from Wood-Burning Biomass Boilers

Measurement and Modelling of Fine Particulate Emissions (PM10 & PM2.5) from Wood-Burning Biomass Boilers

Report to The Scottish Government 26 September 2008 The views expressed in this report are those of the authors and do not necessarily reflect those of the Scottish Government or Scottish Ministers

Measurement and Modelling of Fine Particulate Emissions (PM10 & PM2.5) From Wood- Burning Biomass Boilers Title Measurement and Modelling of Fine Particulate Emissions (PM10 & PM2.5)

From Wood- Burning Biomass Boilers Customer Scottish Government Customer reference CR/2007/38 Confidentiality, copyright reproduction

This document has been prepared by AEA Energy & Environment in connection with a contract to supply goods and/or services and is submitted in accordance with the terms of the contract to which it applies.

AEA Energy & Environment Glengarnock Technology Centre Caledonian Road Lochshore Business Park Glengarnock Ayrshire KA14 3DD

Tel: 0870 190 6574 Fax: 0870 190 5151

AEA Energy & Environment is a business name of AEA Technology plc AEA Energy & Environment is certificated to ISO9001 and ISO14001 Author Name John Abbott, Robert Stewart, Stephen Fleming, Ken

Stevenson, Jo Green and Peter Coleman Approved by Name Ken Stevenson Signature

Date 26/09/2008

© Crown copyright 2008

ISBN 978-0-7559-7296-8

The Scottish GovernmentSt Andrew’s HouseEdinburghEH1 3DG

Produced for the Scottish Government by RR Donnelley B58366 11/08

Published by the Scottish Government, November 2008

Measurement and Modelling of Fine Particulate Emissions From Wood- Burning Biomass Boilers

AEA Energy & Environment iii

Executive summary

The Scottish Government encourages the adoption of biomass combustion in order to reduce emissions of greenhouse gases, mitigate against climate change effects and improve energy security and rural development. In addition, as part of the Renewable Energy Framework, The Scottish Government is committed to the growth of the biomass market, particularly in areas not connected to the gas grid network. However, combustion of biomass, along with many other industrial, commercial and transport activities, leads to emissions of air pollutant species that are potentially harmful to human health. Within Scotland (and the remainder of the UK) there is relatively little knowledge or understanding of the possible scale of and impact of pollutant emissions from biomass combustion. As part of the UK Air Quality Strategy, Scotland has adopted challenging Air Quality Objectives for particulate matter in the atmosphere in order to provide enhanced protection of human health. However, in several Scottish cities the Objectives set in the Air Quality Strategy are already closely approached or exceeded. This is the case for Dundee and Edinburgh and these cities were therefore selected for this detailed study to evaluate the potential cumulative impact of biomass boilers on particle concentrations in urban areas. A key component of this study was the inclusion of specific detailed measurements of particle emissions from a range of typical small-scale biomass boilers installed and operational in urban areas throughout Scotland. In total, 6 boilers were tested to determine emissions of PM10 and PM2.5 particle size fractions1. The boilers chosen for the test programme cover a range of manufacturers, sizes and fuel types. The results of these tests and a review of available literature indicated a wide range of emission factors. Based on these measurements, and the literature review, two emission factors2 of 20g/GJ and 60g/GJ were selected as representative of the range of boilers tested. These values were also found to be generally consistent with the biomass emission factors reported elsewhere. However, it is recognised that this is a relatively small sample and it is restricted to a specific boiler capacity range and, hence, extrapolation of the results to other cities with potentially different biomass boiler installations needs to be undertaken with caution. Lower emission factors can be achieved by means of more effective abatement technologies, but there is currently no requirement to apply these technologies. Unabated emissions from some plant could be greater. In this study a number of important assumptions relating to the likely profile of typical biomass boiler installations have been made. In particular that the maximum local contribution to annual mean particulate matter concentrations from each individual plant operating at capacity is limited to less than 1μg m-3. (In this study, it has been assumed that this will be achieved by use of an appropriate chimney height. However, other measures, such as, additional emission abatement control systems, fuel type and boiler selection could be used to achieve the same outcome.) Information from Dundee City Council and The City of Edinburgh Council was used to prepare scenarios for possible biomass implementation in 2010 and 2020. The 2010 scenario was developed using details of existing planning applications for biomass boilers in both cities. It was assumed that all of these boilers would be granted planning permission and be installed by 2010. In order to assess the potential impact of biomass combustion on air quality in Dundee and Edinburgh in 2020, it was necessary to estimate where the biomass combustion would occur and the quantities of heat to be provided. Potential biomass installations were identified from local development plans together with assumed property replacement and renovation rates3. This provided an estimate of the distribution of biomass combustion sources throughout both cities.

1 PM10 and PM2.5 particle size fractions relate to particulate matter nominally smaller than 10μm and 2.5μm aerodynamic diameter respectively 2 Emission factors relate the rate of emission of pollutant species to a given activity. For a combustion process this is typically the mass of pollutant species (in grammes) per unit of fuel used or, as in this case, the mass of pollutant emitted in grammes (g) to the energy input in gigajoules (GJ) 3 The potential biomass installations were identified for the purposes of this assessment only and the inclusion in the assessment does not imply that the identified installations would be approved or that it would be practical, economic or desirable to install biomass combustion at these locations.

Measurement and Modelling of Fine Particulate Emissions (PM10 & PM2.5) From Wood- Burning Biomass Boilers

iv AEA Energy & Environment

Air quality modelling, using recognised and validated air quality models, was then undertaken for each scenario in each city using the two emission factors derived from the emission monitoring programme. The modelling of particulate concentrations for 2010 shows that the potential impact of the current proposed biomass installations for both Dundee and Edinburgh for both the 20g/GJ and the 60g/GJ emission factor cases is likely to be less than 0.1μg m-3 except in the immediate vicinity of the proposed installations. The modelled PM10 concentration arising from all other sources in 2010 is in the range 14 to 20μg m-3 in these city centre areas and hence, the biomass contribution is in the range 0.5 –0.7%. The model for 2020, using the 20g/GJ emission factor, shows that the effect of biomass combustion is likely to increase annual mean PM10 concentrations across much of the city centres for both Dundee and Edinburgh by 0.2-0.5μg m-3. For an emission factor of 60g/GJ the model shows increases in particulate concentrations of 0.5-1.0μg m-3 across large parts of both cities. The modelled PM10 concentration arising from all other sources in 2020 is in the range 14 to 20μg m-3 in these city centre areas and hence, the biomass contribution is in the range 1 – 7%. The Scottish Air Quality Objective for annual mean PM2.5 is not predicted to be exceeded at any background locations for any scenario in either Dundee or Edinburgh. The UK has also set a PM2.5 exposure reduction target of 15% by 2020 in urban background areas. The business as usual scenario without biomass installations indicates this target will not be achieved. The combined impact of large-scale uptake of biomass installations, under the conditions assumed in this study could increase the difficulty in achieving this target. Additional controls on emissions from individual boilers could be explored to minimise this impact. The modelling study demonstrates that biomass boilers will not be the major source of PM10 or PM2.5 in urban areas. However, in areas that are already close to PM10 Air Quality Objectives the additional contribution of biomass may lead to an exceedence at some city background locations. Note that this result applies to urban background concentrations and higher particle concentrations may be seen in areas close to other specific sources. As part of this study screening tools have been developed to assist Local Authorities to assess the impact of both individual and multiple boiler applications. The individual installation tool will allow Authorities to make informed judgements on the impact of biomass combustion on air quality and the potential need to specify control measures. Emissions from individual boilers can be controlled by boiler design, specification and rating, fuel type and quality, emission abatement equipment and/or chimney height specification. The combined impact tool will help to identify high-density housing or industrial areas where single large district or community heating schemes may be more appropriate, and have less impact on air quality, than many individual smaller boilers. For example, at one large proposed housing development in Edinburgh, this study shows that use of a small number of centralised biomass boilers may contribute 0.5-1μg m-3 to PM10 and PM2.5 concentrations, compared to a contribution of 2-5μg m-3

for individual heating systems. Currently, the Clean Air Act is the main legislative instrument for the control of emissions from small and medium scale boilers. However this Act was developed primarily to control emissions from coal combustion and is not entirely appropriate to biomass combustion in modern appliances. The Act focuses on visible smoke and larger particle emissions rather that the smaller particle size fractions considered in this report. The Act may therefore need to be revised to provide greater consistency with current Air Quality Objectives. In the light of the findings of this study there is a need to review the provisions of the Clean Air Act and to consider the way the planning system operates in practice, so as to take better account of the potential cumulative air quality impacts of district level biomass boilers in urban areas to help ensure that fine particulate levels do not exceed national and EU limit values. In addition, potential costs and benefits of emission abatement equipment, such as particulate filters, to reduce PM10 and PM2.5 emissions could usefully be explored for certain boilers, especially in urban areas where levels are close to EU or national objectives for air quality. However, investigation of specific changes to the Clean Air Act, planning guidance and cost benefit analysis are beyond the scope of this report.


AEA Energy & Environment v

This study has focused on Dundee and Edinburgh. For other areas, the screening tools will allow Local Authorities to take account of the likely different background particle concentration arising from other sources in these areas.


vi AEA Energy & Environment

Table of contents

1 Introduction ...................................................................................................... 1 1.1 Drivers for biomass use in Scotland...................................................................................... 1 1.2 Background to potential air quality impacts of biomass combustion..................................... 2

1.2.1 Airborne Particulate Matter ............................................................................................ 2 1.2.2 Emissions from biomass boilers..................................................................................... 3

1.3 Overview of the Scottish Biomass Study .............................................................................. 5 1.4 Clean Air Act.......................................................................................................................... 6

2 Development of emissions factors for biomass combustion ...................... 8 2.1 Emissions measurements ..................................................................................................... 8

2.1.1 Boiler selection............................................................................................................... 8 2.1.2 Testing methodology.................................................................................................... 11 2.1.3 Results ......................................................................................................................... 11 2.1.4 Derivation of emission factors for use in the model ..................................................... 12

2.2 Comparison with existing emission factors ......................................................................... 13 2.3 Comparison with the London biomass study ...................................................................... 15

3 Scenario development and air quality modelling........................................ 16 3.1 Dispersion modelling ........................................................................................................... 16 3.2 Background concentrations................................................................................................. 17

3.2.1 Emissions from domestic, transport, commercial, industrial and agricultural sources 17 3.2.2 Emissions from large point sources ............................................................................. 18 3.2.3 Emissions from other sources throughout UK and Europe.......................................... 18 3.2.4 Emissions of sulphur dioxide and nitrogen oxides....................................................... 18 3.2.5 Coarse particulate matter from wind-blown dust, sea salt and other natural sources. 19 3.2.6 Verification of modelled concentrations against measured concentrations................. 19

3.3 Overview of scenario development ..................................................................................... 20 3.4 Dundee modelling................................................................................................................ 23

3.4.1 Recent year, 2006: Dundee ......................................................................................... 23 3.4.2 Business as usual, 2010: Dundee ............................................................................... 25 3.4.3 Future year 2010, with proposed biomass: Dundee .................................................... 27 3.4.4 Business as usual, 2020: Dundee ............................................................................... 30 3.4.5 Future year 2020, with substantial biomass combustion: Dundee .............................. 31 3.4.6 Summary for Dundee ................................................................................................... 42

3.5 Edinburgh modelling............................................................................................................ 44 3.5.1 Recent year, 2006: Edinburgh ..................................................................................... 44 3.5.2 Business as usual, 2010: Edinburgh............................................................................ 47 3.5.3 Future year 2010, with proposed biomass: Edinburgh ................................................ 49 3.5.4 Business as usual 2020: Edinburgh............................................................................. 51


AEA Energy & Environment vii

3.5.5 Future year 2020, with substantial biomass combustion: Edinburgh .......................... 52 3.5.6 Total concentrations..................................................................................................... 55 3.5.7 Summary for Edinburgh ............................................................................................... 58

4 Air Quality Screening Tool for Biomass Combustion in Scotland ............ 60

5 Conclusions.................................................................................................... 61

6 References...................................................................................................... 63

Appendices

Appendix 1 Emissions Test Results

Appendix 2 Edinburgh Scenario Development and Modelling Results for 2020 with Substantial Biomass Combustion

Appendix 3 Air Quality Screening Tool for Biomass Combustion in Scotland


AEA Energy & Environment 1

1 Introduction The Biomass Action Plan for Scotland and the proposed Renewable Heat Action Plan formulate policy and action within Scotland to encourage the take up of biomass as a heat fuel source. This is part of a range of measures to reduce CO2 emissions, to reduce energy costs and to gain economic advantages from the deployment of all forms of renewable energy. However, it is clear that this policy must be aligned with the need for clean air and a healthy environment. The Scottish Government re-affirms its commitment to delivering clean air for a good quality of life in the 2007 Air Quality Strategy for England, Scotland, Wales and Northern Ireland. The Scottish Government has adopted more challenging air quality objectives than the remainder of the UK for both PM10 and PM2.5. In many urban areas of Scotland, reductions in ambient particle concentrations are already required to achieve these objectives and a number of local Air Quality Management Areas have been designated, and associated Air Quality Action Plans prepared, to work towards achieving these reductions. Hence, especially in these areas, the introduction of biomass boilers needs to be carefully considered and evaluated. The Scottish Government commissioned AEA Energy and Environment to undertake a detailed study of the likely cumulative impact of particle emissions from wood burning biomass boilers on air quality in urban areas. Two cities were selected for the study – Dundee and Edinburgh.

1.1 Drivers for biomass use in Scotland The Scottish Government is committed to the growth of the biomass market, particularly off the gas grid, as part of its Renewable Energy Framework. The Biomass Action Plan for Scotland (Scottish Executive, 2007) sets out a coordinated programme for the development of the biomass sector in Scotland. It summarises the various existing activities, and provides a framework under which they will be coordinated and also supplemented by further actions. The Scottish Biomass Support Scheme4 provided grant funding aimed at promoting use of biomass (primarily wood fuel) in Scotland. The scheme provided grants to support supply chain, heat and CHP installations. The key drivers of the scheme were:

• The strategic transformation of the Scottish biomass wood fuel sector market; • Maximising carbon savings; • Supporting rural economies by creating sustainable green jobs; and • Contributing to renewable energy targets.

Around 60 biomass projects across Scotland have received £7 million. This is estimated to reduce CO2 emissions by up to 20,000 tonnes a year.

4 http://www.usewoodfuel.co.uk/ScottishBiomassSupportScheme.stm


2 AEA Energy & Environment

1.2 Background to potential air quality impacts of biomass combustion

All combustion appliances emit a range of air pollution species which may be harmful to human health. The air pollutants emitted include oxides of nitrogen, oxides of sulphur and particulate matter. However, these pollutants are also emitted from a range of other sources. Of particular concern for biomass combustion is the emission of particulates (PM10 and PM2.5). The section below describes the main UK sources of particulates and their potential effects on human health and the likely contribution from emissions from biomass boilers.

1.2.1 Airborne Particulate Matter

Particulate Matter (PM) consists of a wide range of materials arising from a variety of sources. PM is generally categorised on the basis of the size of the particles. The most frequently used metric is PM10, i.e. particles with a diameter less than 10 micrometres (μm) in diameter. Concentrations of PM2.5 (i.e. particles with a diameter less than 2.5 μm in diameter) are also becoming more important following the introduction of a PM2.5 UK Air Quality Objective (Defra, 2007). Both short-term and long-term exposure to ambient levels of PM are consistently associated with respiratory and cardiovascular illness and mortality as well as other ill-health effects. The Air Quality Objectives for PM are primarily based on health effects. The Department of Health’s Committee on the Medical Effects of Air Pollution (COMEAP) estimated that in Great Britain in 1996, PM10 pollution was associated with around 8,100 deaths and 10,500 hospital admissions being brought forward in sensitive sections of the population (COMEAP, 1998). This was associated with short-term (acute) exposure and it is likely that the health impacts of long-term (chronic) exposure were greater. The main effects of PM are inflammation of the airways causing problems in people with lung disease and enhancing sensitivity in people with hay fever and asthma. It may also alter the ability of the blood to clot and circulation of red- blood cells (AQEG 2005). It is not currently possible to discern a threshold concentration below which there are no effects on the whole population’s health. Recent reviews by WHO and Committee on the Medical Effects of Air Pollutants (COMEAP) have suggested exposure to a finer fraction of particles (PM2.5), which typically make up around two thirds of PM10 emissions and concentrations, give a stronger association with the observed ill health effects. There is a wide range of emission sources that contribute to PM10 concentrations in the UK (AQEG, 2005). These sources can be divided into 3 main categories:

• Primary particle emissions which are derived directly from combustion sources, including road traffic, power generation, industrial processes etc.

• Secondary particles which are formed by chemical reactions in the atmosphere, and comprise principally of sulphates and nitrates.

• Coarse particles which comprise of emissions from a wide range of sources, including resuspended dusts from road traffic, construction works, and mineral workings.

In the UK, the largest anthropogenic sources are stationary fuel combustion and transport. Road transport gives rise to primary particles from engine emissions, tyre and brake wear and other non-exhaust emissions. Other primary sources include quarrying, construction and non-road mobile sources. Secondary PM is formed from emissions of ammonia, sulphur dioxide and oxides of nitrogen as well as from emissions of organic compounds from both combustion sources and vegetation. Figure shows the emission of PM10 by UNECE source category as reported by the e-digest of Environmental Statistics5. Emissions estimates for 2005 for the UK suggest that 13% of PM10 emissions are derived from commercial and residential combustion plant whilst 24% of PM10 emissions are derived from road transport.

5 http://www.defra.gov.uk/environment/statistics/airqual/alltables.htm



Figure 1.1: Estimated emissions of PM10 by UNECE source category.

1.2.2 Emissions from biomass boilers

Biomass boilers could, potentially, be a significant source of particulate matter. Hence, concern has been raised within the air pollution community at the possible widespread adoption of biomass boilers, especially where these are located in urban areas. The Clean Air Act (see Section 1.4) already regulates emissions from commercial and domestic premises in designated Smoke Control Areas. However, this legislation was developed in the 1960’s and is primarily aimed at coal combustion and not appropriate to the modern pollution situation and control of particulate matter emissions from biomass boilers of fractions PM10 and below. The specific concern is that the majority of boilers in urban areas are now gas fuelled, and hence boiler emissions are significantly lower than the Act's requirements. Therefore, although biomass boilers may meet Clean Air Act standards, in many circumstances they still have the potential to produce PM10 emissions that are worse than the current gas equivalent. In addition, under the Environment Act 2005, Local Authorities throughout the UK have a statutory duty to review and assess air quality in their Council area and identify any likely exceedences of the Air Quality Objectives. All Authorities must assess air quality in their area against the objectives set for NO2, PM10 and SO2 (and other gases). At present there is not a requirement for Authorities to assess against the PM2.5 Objective. This is to be handled at a national level. The Air Quality Objectives for PM10 and PM2.5 that apply in Scotland are given in Table 1.1.

0

100

200

300

400

500

600

1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Year

Tonn

es ('

000)

Energy industries Manufacturing industries and constructionRoad transport Other transportCommercial and institutional ResidentialAgriculture and forestry fuel use Industrial procesesOther



Table 1.1: Air Quality Objectives for PM10 and PM2.5 Scotland.

Air Quality Objective Pollutant

Concentration Measured as Date to be achieved by

Particles (PM10) (gravimetric)a (Authorities in Scotland onlyb)

50 µg m-3 not to be exceeded more than 7 times a year 18 µg m-3

24 hour mean annual mean

31.12.2010 31.12.2010

Particles (PM2.5) (gravimetric)a (Authorities in Scotland only)

12µg m-3

target of 15%reduction in concentration at urban background

Annual mean Annual mean

2020 Between 2010 and 2020

a. Measured using the European gravimetric transfer sampler or equivalent. b. These 2010 Air Quality Objectives for PM10 apply in Scotland only, as set out in the Air Quality (Scotland) Amendment Regulations 2002.

Currently five Scottish Local Authorities have declared Air Quality Management Areas (AQMA) due to exceedences of the PM10 Air Quality Objectives. A further 5 have declared on other pollutants. The Councils that have declared and the pollutants that they have declared against are listed in Table 1.2. Where an AQMA has been declared then the Authority is required to produce an Air Quality Action Plan defining actions to be taken to improve air quality.

Table 1.2: Summary of Air Quality Management Areas declared in Scotland6.

Pollutant declared for Council Number of AQMAs

declared NO2 PM10 SO2

Aberdeen City 1

Edinburgh City 2

Glasgow City 3

Dundee City 1

East Dunbartonshire 1

Falkirk Council 1

Midlothian Council 1

North Lanarkshire 3

Perth and Kinross 1

Renfrewshire 1

6 Further information available at http://www.scottishairquality.co.uk/laqm.php



1.3 Overview of the Scottish Biomass Study The primary aim of this study was to quantify any likely air quality impacts from emissions of particulate matter from biomass boilers and to examine these in relation to the Air Quality Objectives for Scotland. The specified Project Objectives were as follows:

• To measure particulate emissions (PM10 & PM2.5) from the most widely used types of biomass boilers. To model PM10 levels in Edinburgh and Dundee based upon these emission figures, using local meteorological data, given the number of planned and/or existing biomass boilers, to evaluate if PM10 levels would exceed Air Quality Strategy Objectives for Scotland. To provide advice on the potential cumulative impacts of PM10 emissions from biomass boilers in urban smoke control areas and compare this to rural sites.The project has been overseen at

all stages by a project Steering Group convened by The Scottish Government. The Steering group members included representatives from the following organisations:

• Scottish Renewables Forum • Edinburgh City Council • Dundee City Council • Scottish Government Renewables Policy Unit • Scottish Government Water, Air, Soils and Flooding Division • Defra (Air Quality and Industrial Pollution Programme) • SEPA • Forestry Commission Scotland

The Steering Group were consulted on a number of the significant project decisions. These included:

• The choice by AEA of a representative selection of currently operational boilers for emissions testing and

• The range of emissions scenarios to be modelled. AEA developed detailed emissions scenarios in consultation with Dundee and Edinburgh Councils. Other specific inputs were provided by individual members of the Steering Group. An overview of the project activities is provided in Figure 1.2.

Figure 1.2: Overview of Project Activities.

Kick–off Meeting

Emissions Data Literature Survey Emissions Measurement

Modelling Scenarios

Modelling

Advice to LAs and Tech Guidance AQ Impact of Biomass

Final Report

Clean Air Act Edinburgh, Dundee

Biomass Strategy



The key project stages are described in the Chapters of this report. Chapter 2 describes the emission measurement programme undertaken as part of the project to measure real-life emissions from boilers currently operation in Scotland. Chapter 3 discusses the development of the scenarios for the likely future deployment of biomass boilers based on current and anticipated planning applications and National and Local biomass uptake strategies. The emissions data from Chapter 2 and the agreed biomass uptake scenarios were then utilised in the air quality dispersion modelling to evaluate the likely impact on air quality. Chapter 3 also presents the modelling results. Chapter 4 presents details of screening tools that have been developed to assist Local Authorities in assessing the impact of both individual and multiple boiler applications in Scotland. Chapter 5 brings together the main conclusions and recommendations of the work. Figure 1.2 also shows that key aspects that AEA brought to the project were the linkages to the Clean Air Act (http://www.uksmokecontrolareas.co.uk/index.php) and linkages to the Review and Assessment Technical Guidance for Local Authorities. The close linkage with the Clean Air Act ensures that relevant findings can be incorporated into the future operation of the Act within the UK. Similarly, the close linkage with the Review and Assessment Technical Guidance for Local Authorities means that the results of this project can be fed into the current process of update of this document - see Appendix 3. This will ensure that the findings and the assessment methodologies developed are available to all Scottish Local Authorities for their use in Review and Assessment and for the assessment of biomass boiler planning applications. The draft updated Technical Guidance is currently out for public consultation7 and it is anticipated that the results of this study will be incorporated into the final document to be published in December 2008.

1.4 Clean Air Act The Clean Air Act is likely to be the main regulatory control that Local Authorities will have over biomass burners. Particulate emissions from residential and industrial combustion sources are controlled under the Clean Air Act 1993. The Clean Air Act (CAA) was developed to address the impact of air pollution on public health following smog events in London in 1954. The 1993 Act combines and repeals the 1956 and 1968 Acts along with some other changes such as metrication. The Act restricts smoke emissions from premises, applies particulate emission limits to industrial combustion units and includes the following powers:

• Prohibits the emission of dark smoke from chimneys unless within the limited periods allowed by the dark smoke permitted periods regulations (s1);

• Prohibits the emission of dark smoke from industrial or trade premises unless it was inadvertent and all practical steps taken (s2);

• Requires all new furnaces, other than domestic boilers less than 16.12kW output (defined as domestic furnaces), to be capable of operating smokelessly and to be notified to the local authority (s4);

• Allows the Secretary of State to prescribe emission limits on grit and dust from furnaces other than domestic furnaces (s5);

• Prohibits the use of a furnace other than a domestic furnace in a building or outdoors which burns pulverised fuel, solid fuel at 45.4 kg/h or more or liquid and gas fuels at 366.4 kW or more unless it has grit and dust arrestment plant fitted which have been agreed by the local authority or unless the Local Authority has been satisfied that the emissions will not be prejudicial to health or a nuisance (s6);

• Where a furnace is burning pulverised fuel, solid fuel at 45.4 kg/h or more or, liquid and gas fuels at 366.4 kW or more the Local Authority may direct that measurements of the dust emissions are made (s10). However, if the furnace is burning solid matter at less than 1.02 te/h or liquid or gas at 8.21 MW or less then the Local Authority can be required to carry out

7 http://www.scotland.gov.uk/Topics/Environment/Pollution/16215/6166



the measurements (s11);

• Allows the local authority to request the occupier of a building to provide such information as may be reasonably required on the furnaces in the building and the fuels or wastes burnt on them (s12);

• Prohibits the use of furnace with a chimney which burns pulverised fuel, solid fuel at 45.4 kg/h or more or liquid and gas fuels at 366.4 kW or more unless the chimney height has been approved by the Local Authority following the provision of relevant information by the applicant, unless the application was made and the Local Authority did not respond within 4 weeks or a longer time mutually agreed (s14 15);

• Allows Local Authorities to create smoke control areas (s18) in which smoke emission is prohibited (s20) unless arising from the burning of authorised fuel or from the use of an exempt appliance;

• Allows the Secretary of State to authorise fuels (s20) and exempt classes of fireplaces (s21) which he is satisfied can be used without producing smoke or a substantial quantity of smoke (details of authorized fuels and appliances can be found here http://www.uksmokecontrolareas.co.uk/);

• Prohibits the acquisition or delivery of solid fuel in a smoke control area other than to an appliance exempt under s21;

• Requires occupiers of buildings other than private dwellings or caravans when requested by the Local Authority to return estimates of the emission of pollutants from the premises (s36).

The rating of 45.4 kg/h for solid wood fuels will imply a range of heat input rates depending on the moisture content of the wood and the implied calorific value, i.e. increased moisture content leads to lower calorific values. For example, a fuel with a calorific value of 10MJ/kg would represent 126 kW (input), and at 20 MJ/kg this would imply 252 kW (input). Hence, appliances burning low moisture content biomass fuels (for example pellets with low moisture content) would be covered by the arrestment plant requirements (s6) and chimney heights provisions (s14-15) of the act at larger capacities than appliances burning biomass with higher moisture content (for example part dried wood chip or green timber) and associated lower calorific value. Smoke control areas are primarily urban areas that have had a concentration of industry and/or coal-fired dwellings. Many urban regions are covered by smoke control areas. Unfortunately, due to the passage of time and the age and number of the individual orders passed to establish smoke control areas there are no easily accessible records of the location of smoke control areas in some authorities. In smoke control areas either authorised fuels or exempt appliances must be used. While biomass based fuels easily pass the requirement that authorised fuels have a sulphur content below 2% on a dry basis they normally struggle to pass the smoke test (BS3841) to become authorised fuels. Hence, to use biomass in a smoke control area it must be burnt in an appliance which is exempt under Section 21. Exempted appliances have undergone type-approval emission tests to determine if they can operate within prescribed particulate emission limits which are related to appliance capacity/output. Exemption testing for appliances is straightforward albeit somewhat dated and with relatively few test facilities able to undertake the test work. The Clean Air Act 1993 potentially controls PM emissions greater than 10um in aerodynamic diameter for wood combustion activities up to 20 MWth (the threshold above which the PPC Regulations apply). However, if the fuel is deemed to be a waste (or derived from a waste) then PPC Regulations apply at a lower net rated thermal input.



2 Development of emissions factors for biomass combustion

This section details the rationale behind the selection of boilers for emissions testing, details the results of the tests and discusses the choice of emissions factors for use in the modelling phase. These monitoring results are also compared to emissions data from some recent studies and test reports.

2.1 Emissions measurements A total of six boilers were tested within this study to determine real-life emissions of PM10 and PM2.5 of a range of boilers in Scotland. The results from these tests were used to ascertain the most representative emission factors to be used in the modelling work. This section describes the process undertaken to select the boilers, the testing methodology employed and presents the results.

2.1.1 Boiler selection

A range of boilers were selected for testing based on four main criteria:

1) Boiler rating expressed as heat output in kW; 2) Fuel types (pellets, wood chips or logs); 3) Boiler make and model; 4) If external particulate abatement was fitted.

Boiler testing was carried out at six separate sites taking into account a variety of examples within the above criteria. Recognition also had to be made on the availability of the boilers for independent testing. All boilers were tested with the aim of getting real-world operational PM10 and PM2.5 emissions data to provide a reflection of current on-site performance. All boilers were therefore tested under normal operational conditions and under supervision of owners/operators. 2.1.1.1 Boiler Rating It was important that the boilers selected for emission testing were representative of what is currently operating within Scotland. The amount of information available on the size and types of boilers operating was very limited. As part of this study a list of existing plant was compiled to identify what technology was currently being used. The list was generated from accurate information provided by a number of grant funds such as Scottish Biomass Support Scheme, Scottish Enterprise and other grant schemes such as Scottish Community and Householder Renewables Initiative (SCHRI) and Highlands and Island Enterprise (HIE). This information was analysed to determine the location of the boilers, their size and type of fuels used. A total of 128 units were identified as part of this process. The total installed capacity in Scotland was calculate to be 18,428 kW. The existing applications were almost all hot water boilers that ranged from small domestic heating plants at 20 kW to larger commercial boilers at 2000 kW. The average installed capacity was found to be 222 kW and the most common units fitted ranged between 100 and 120 kW. 2.1.1.2 Fuel supply The three main fuel types commonly used are Wood Chip, Wood Pellets and Log Wood. Wood pellets are compressed wood generally made from sawdust and wood shavings and are typically 6-12 mm in diameter and 6-20 mm long. Pellets have the main advantages of being dry and consistent in shape and composition. This allows them to be easily handled and they flow freely from hoppers and through fuel feed systems to the boiler and hence make them ideal as a fuel for automatic feed systems. Pellets however are more expensive than wood chip or log but they have a higher density (600-700 kg/m3) and so can be transported in larger volumes reducing transport costs.



Wood chip can be produced from a number of wood sources and are normally produced by industrial chippers that consist of rotating blade that reduce the larger wood stems to various sizes but typically 15 – 30 mm by 5 –10 mm. The final chip will have the same moisture content as the wood stems and require air drying by either natural means or a drying air floor system. The density of the wood chips is much lower than pellets at 200 – 350 kg/m3 and therefore transport costs are higher. Wood chip quality can be problematic to automatic boiler plant and can cause blockages to feed systems. Log wood, like chips, can be produced from a number of sources but generally is produced from smaller round woods that are of much lower value to forestry and sawmill operations. Good quality log wood will be cut, split and stored in the winter for use the following winter. Logs for automatic boilers are 300 –500 mm long and a maximum of 70 mm diameter and they should be stored under cover with free ventilation to promote good drying. The density of log wood is again much lower than pellets at 300 – 550 kg/m3 and therefore transport cost are higher. 2.1.1.3 Boiler Designs Biomass boiler manufactures offer a very wide and diverse range of units that are specifically designed to meet various efficiency and emission criteria predominantly. Because of this wide diversity of boiler size, design criteria and fuel type it was important to consider testing boilers which were representative of equipment used in Scotland. The range of boilers available can loosely be characterised into three main technology groups. These are type of heating application; fuel type (discussed above) and combustion technology. Boilers can be used to produce hot water or steam. Steam boilers are normally used by the industrial sector for process heating application. Other instances where steam boilers would be used are for larger heating applications where steam to hot water heat exchangers can be employed. These types of boilers can be found, for example, as larger centralised Hospital boiler plants. Hot water boilers can be supplied as low (LTHW), medium (MTHW) or high temperature (HTHW) hot water boilers. This classification is determined by the type of heating system to which the boilers are applied. In nearly all instances the units in Scotland found were of the LTHW type and therefore these were put forward for testing. The biomass boilers in Scotland were comprised of three key types of combustion technology: overfeed; underfeed and moving grates.

• Overfeed stokers are generally used for larger sizes of fuel such as logs. These boilers operate on a downdraft principle where air is forced down through holes in the combustion chamber to a secondary chamber where more air is introduced for final combustion. Logs are automatically fed in from the top in the first combustion chamber. These boilers are generally up to 70 –100 kW and because of the size, feed system and lack of abatement fitted they tend to have the highest emission levels.

• Underfeed stokers are designed generally for smaller wood chips or pellets less than 50 mm where the fuel is fed into the combustion chamber of the boiler by screw conveyors. This type of design covers boiler up to 2MW capacity. Since fuel feed is controlled and abatement technology is used this type of combustion results in lower emissions than the overfeed stokers.

• Moving grates are identified by the way that the grate moves such as vibrating, inclined, horizontal or travelling. This design is a further improvement on the underfeed stoker as it allows for more control of the air and fuel mixing at various stages of the combustion process. This gives the advantages of being able to handle a wider specification of fuel types and moisture contents and is generally applied to larger Industrial applications in excess of 2 MW.

2.1.1.4 Abatement technology Smaller biomass boilers are generally not fitted with any pollution abatement devices as these are generally not required to meet current CAA requirements for emissions. However, most larger new



automatic boilers are fitted with some form of flue gas cleaning device to remove particle (dust) from the flue gas before release to the atmosphere. The dust collection system has to be chosen with respect to the required emission level and the actual operating conditions. For many small grate boilers and some underfeed boilers, single or multi cyclones are sufficient to meet the required emissions. The cyclone removes the coarse fraction but does not remove smaller particles. The cyclones are in some instances fitted internally as an integral part of the boiler plant, however the principle of operation is basically the same. All single cyclone designs apply the same basic principle of inducing the particulate laden flue gases to swirl around inside the cyclone body for sufficient time and with sufficient vigour that grit and dust is centrifuged to the inside wall surface and is carried downwards to the dust outlet. The point of separation of the flue gases from the particulates occurs at the base of the cyclone body, where the gases reverse direction and vortex back upwards to the central clean gas outlet tube. Multi cyclone arrestors perform in a similar way to a single cell but use a number of smaller cells contained in a chamber that is directly fitted to the boiler flue. Other Devices More stringent particle emission requirements can easily be met with an electrostatic precipitator (ESP). The ESP has usually high particle removal efficiency in the complete particle size range. The removal efficiency has a minimum for particles having an aerodynamic diameter around 0.2 mm. ESP’s are widely used for this type of application in Sweden, when the requirements are more stringent or the multi cyclone is unable to meet the requirements. Fabric filter is an alternative when high removal efficiencies are required. It is not widely used for grate boilers firing wood fuels due to the risk for fire. However, fabric filter is used after straw fired boilers, after fluidised bed boilers and after multi cyclones. 2.1.1.5 Final selections made A selection of boilers was included in this study to represent examples of each type of fuel, abatement, boiler rating and combustion technology. The proportion of fuels used was also reflected. The majority of biomass boilers in Scotland use wood chip with only a small number of pellet and log boilers and so only one example each of pellet and log boilers was tested. The selection of boilers for testing was reviewed and discussed by the project Steering Group and a final list agreed. We believe that the resulting range of boilers tested covers an optimum range of currently available boiler sizes and technologies and is a representative sample of boilers currently installed in Scotland, mainly in rural areas. However, it should be noted that it may not be representative of boilers included in the scenario which are outwith the size range and scale of those tested. Table 2.1 lists the critical technical specifications of the final 6 boilers selected for the emission measurement programme.

Table 2.1: Specifications of the 6 Boilers Selected for the Emissions Testing Programme.

Site code Output (kW) Boiler Type Abatement Approved Appliance Fuel Type

A 120 Underfeed none No Chip

B 600 Underfeed single cell cyclone Yes Chip

C 300 Underfeed single cell cyclone Yes Chip

D 220 Moving Grate Internal cyclone Yes Pellet

E 70 Downdraft none No Log

F 400 Moving Grate multi cell cyclone No Chip



2.1.2 Testing methodology

The testing phase of this study was subcontracted to TUV NEL who provide ISO9001 and UKAS accredited emissions monitoring. As well as determining PM10 and PM2.5 concentrations the flue gases were also tested for other pollutants, namely oxides of nitrogen, carbon monoxide and carbon dioxide.

It is important to note that all of the tests were conducted in the same manner, i.e. as they were found in a live operational situation with no involvement from installers or manufacturers to ensure data collected was true reflection of current on site performance.

PM10 and PM2.5 were sampled in accordance with US EPA Method 201A. A fixed flowrate, as near as possible to the isokinetic rate, was selected and the sample was drawn from the centre point of the stack through a filter via a cyclone. The cyclone removed matter with a nominal aerodynamic diameter of 10µm and 2.5µm depending on the test required. The remaining material (<10µm or <2.5µm) was collected on a filter and the mass determined gravimetrically at a laboratory according to TUV NEL’s internal procedure WI/PE2/962 which references BS EN 13284.

Flue gas concentrations of CO and CO2 were determined using a non-dispersive infra-red analyser. Flue gas was sampled according to TUV NEL’s internal procedure Work Instruction WI/PE2/971 which references ISO 12039. The flue gases were extracted, dried and passed through a measuring cell. Infra-red radiation tuned to a frequency absorbed by the gas was transmitted through the cell and the attenuation of the beam was recorded.

Flue gas concentration of oxides of nitrogen, NOx was determined by following TUV NEL’s internal procedure Work Instruction WI/PE2/971 which references ISO 10849. The flue gases were extracted, dried and passed through an analyser operating on the chemiluminescence principle where ozone is added to the sample gas which oxidises the NO contained in the sample into NO2. A NOx converter reduces any NO2 in the initial sample to NO. The portion of the NO2 in an excited state radiates light when it returns to normal state. The light emitted from this reaction is detected and amplified by a photomultiplier tube.

The stack conditions were also measured. The flue gas concentration of oxygen was determined using a Zirconia cell oxygen analyser following TUV NEL’s internal procedure Work Instruction WI/PE2/971 which references ISO 12039. These devices make use of the fact that oxygen ions become highly mobile in Zirconia (ZrO2) heated to temperatures above 600°C. It is therefore possible to use Zirconia as a solid electrolyte for an oxygen sensor provided it is heated (typically 750°C). The stack gas velocity, flow rate and moisture content are integral to the PM10 and PM2.5 measurements and the measurement techniques are based on TUV NEL’s internal procedure WI/PE2/961 which references BS EN 13284. Velocity was determined by means of a pitot tube and manometer, temperature by means of a thermocouple and the moisture content was determined gravimetrically.

2.1.3 Results

The results from the monitoring are provided in detail in Appendix 1. Table 2.2 presents the particulate emissions data in g/GJ for each test and the average and median for each boiler. The third PM10 test for boiler B was removed from the dataset because there was an uncharacteristically low flow rate during that period of testing compared to the rest of the tests. The PM10 result from the last test of boiler E was not removed as there were no unusual characteristics noted during this test and so it was deemed to be a real example of emissions from the boiler (which had no abatement equipment fitted). However, we have no information on how frequently or infrequently such events may occur.



Table 2.2: Particulate emissions by test and averaged over all tests (g/GJ).

Test No. Site

1 2 3 4 5 6 7 Mean Median

PM10

A 26.6 30.9 27.9 - - - - 28.5 27.9 B 55.8 54.3 - - - - - 55.1 55.1 C 19.3 10.9 14.6 - - - - 14.9 14.6 D 45.2 50.3 92.8 59.8 66.7 45.2 62.3 60.3 59.8 E 3.1 25.2 28.3 32.5 18.6 18.0 355.1 68.7 25.2 F 22.1 34.4 16.1 23.4 20.9 30.5 31.2 25.5 23.4

PM2.5

A 22.5 5.6 19.9 - - - - 16.0 19.9 B 47.1 39.1 40.5 - - - - 42.2 40.5 C 22.0 14.4 11.7 - - - - 16.0 14.4 D 28.2 34.1 46.0 69.6 87.2 47.9 37.1 50.0 46.0 E 2.4 17.2 24.1 32.4 19.2 18.8 15.3 18.5 18.8 F 19.2 18.5 20.0 20.1 17.5 15.7 19.9 18.7 19.2

Using the fuel test data and the operational data recorded for each site it was possible to estimate the firing rate of each boiler during the tests. This was calculated for each hour of operation that the tests were carried out and Table 2.3 shows the range of firing rate for each boiler. Boilers C, D and F were operating at lower loads than the appliance rating. These data are still valid for this study, however, as it was the aim to monitor emissions from boilers in their normal operational state. This perhaps a good indication that boilers are not often operated at their full potential. There was no correlation between boiler rating and emission rates or indeed the firing rate and emissions rates.

Table 2.3: Energy rating of each boiler versus firing rate (input range) during testing.

Site Boiler rating (kW) Calculated input range (kW net)

A 120 154-176

B 600 545-645

C 300 102-184

D 220 35-92

E 70 55-100

F 400 133-200

2.1.4 Derivation of emission factors for use in the model

The results from the six boilers show a range in median emission rate for particulate (both PM10 and PM2.5) of 14.4 g/GJ to 59.8g/GJ and a range in the mean emissions rate of 14.9 g/GJ to 68.7 g/GJ. It was decided to model for a best and worst case scenario – i.e. making two assumptions: firstly, that all boilers installed would be operating close to the lower emission rate and secondly that they would all be operating close to the higher emission rate. To be broadly consistent with the test figures gathered an upper level of 60 g/GJ and a lower value of 20 g/GJ was taken forward to the modelling phase. It is recognised that this is a relatively small sample and restricted to a specific boiler capacity range and,



hence, extrapolation of the results to other cities with potentially different biomass boiler installations needs to be undertaken with caution. To help to put these emissions into context Table 2.4 shows some approximate emission factors for other fuels. These were derived from the UK National Atmospheric Emission Inventory (NAEI) emission factors and making some assumptions about the efficiency of plant for each fuel.

Table 2.4: Approximate emission factors (energy input) from other sectors within the combustion industry.

Fuel Emission factor (g/GJ)

coal 120 fuel oil 12 gas oil 5

natural gas 1 Based on the emission factors for biomass derived for this study, particulate emissions from biomass are typically lower than small coal fired plant but higher than oil and gas. Hence, where a biomass boiler is a replacement unit an important consideration is what type of combustion appliance is being replaced.

2.2 Comparison with existing emission factors In order to put the measured emission rates into context they have been compared to emissions data from some recent studies and test reports A very comprehensive particulate emissions study was undertaken recently by the International Energy Agency (IEA) Bioenergy Task 32 (Nussbaumer et al, 2008). This study collected emission data directly from research institutes and universities, and considered data available from literature sources. Input was provided from the 17 institutions in the seven member countries of the IEA Task 32 (Austria, Denmark, Germany, Norway, The Netherlands, Sweden, and Switzerland). A range of data were analysed to include results from ideal operation, typical results at in-service operation and worst results at very bad handling. This therefore provided a good comparison dataset to the in-service testing that was carried out in Scotland. The study looked at all biomass combustion equipment from a wide range of applications. The main conclusions from the report relevant to this study were the typical measured particulate emissions for logwood, pellets and chip. Table 2.5 shows a summary of the results.

Table 2.5: Average particulate emissions reported in Nussbaumer et al (2008).

Boiler type Typical PM emission factors (g/GJ)

Log boiler 105 Underfeed boiler using wood chip 80 Grate boilers using wood chip 60 Pellet boilers 30

Table 2.6 compares the emissions results from the monitoring of the six Scottish boilers with the typical emission rates reported in the IEA Bioenergy Task 32 report. It can be seen that all cases the Scottish emissions data were found to be lower than the typical IEA figures. This is not unexpected as the IEA study reported emissions figures from a much wider range of boilers encompassing installations of a much wider age range than those monitored in Scotland. It also specifically looked at “worse” case emissions as well as usual in-operation and ideal operation data. This provides perhaps a clearer picture of real emissions from boiler plant currently operational across Europe but is less relevant to this study where the objective it to look at emissions from more modern boilers with a view to reporting future trends with the installation of new, more efficient equipment.



Table 2.6: Comparison of monitoring data in Scotland with typical emissions reported from the IEA (Nussbaumer et al, 2008).

Site code Boiler Type Fuel Type

Average PM10 emission factors

(g/GJ) Typical IEA PM emission factor

A Underfeed Chip 28.5 80 B Underfeed Chip 55.1 80 C Underfeed Chip 14.9 80 D Moving Grate Pellet 60.3 60 E Downdraft Log 68.7 105

F Moving Grate Chip 25.5 60 The data from the Scottish tests were also compared to both the specific manufacturers test data, where available, and also some average statistics derived from over 200 type-approval test reports from the Austrian test-house Bundesanstalt für Landtechnik (BLT (Federal Institution for Agricultural Engineering)) which were averaged for fuel use as opposed to boiler type. These are presented in Table 2.7. A comparison with both the test data for the specific model monitored in Scotland and the average of results from BLT show that type-approval test results are generally below the real-world emissions as measured in Scotland and presented by Nussbaumer and co-workers (2008). Again this is not unexpected as the type-approval tests are undertaken under controlled conditions such as steady heat load and uniform fuel feed. In contrast boilers in real-world situations are subject to fluctuating heat demand and are unlikely to be used constantly at their optimum running criteria.

Table 2.7: Comparison of monitoring data from Scotland with typical emissions reported test reports.

Site code Fuel Type

Average PM10 emission factor

(g/GJ)

Model- specific PM test data

(g/GJ)

Average of BLT PM test data

(g/GJ)

A Chip 28.5 19 20 B Chip 55.1 n/a 20 C Chip 14.9 37 20 D Pellet 60.3 18 17 E Log 68.7 n/a 17

F Chip 25.5 n/a 20 This exercise has shown the wide range of emission rates that are available in the literature. These reflect the wide range of factors that can affect the results of such testing. These include the boiler model and combustion technology used, the presence or absence of abatement technologies and the operation mode during testing. The use of real-world monitoring data from existing boilers in Scotland has gone some way to control for all of these factors by undertaking modelling work based on real emissions from boilers in operation.



2.3 Comparison with the London biomass study The work carried out for the Scottish Government follows earlier studies of the impact of biomass combustion on air quality in London (Abbott et al, 2007). The London study was an initial assessment of the potential impact. It made various simplifying assumptions:

1) that the spatial distribution of new biomass combustion throughout London would be similar to that for gas;

2) that sources of biomass combustion could be represented in the modelling as low level volume sources throughout the city;

3) the rates of emission were based on default emission factors from the CORINAIR database. The London study predicted that concentrations of particulate matter in the centre of the city would be substantially increased by biomass combustion. A much more detailed approach has been adopted for this Scottish study. The key differences are:

1) new biomass emissions sources have been assumed to be installed where land is available for development, often on the outskirts of the city;

2) emission sources for large new developments have been represented as elevated point sources to take account of the dispersion of pollutants from chimneys;

3) the rates of emission were based on measurements from biomass combustion sources recently installed in Scotland. The emissions rate for PM10 used in the London study was 66 g/GJ. The testing undertaken in Scotland has illustrated that this was a very conservative estimate with average boiler emissions of PM10 ranging from 14.9 g/GJ to 68.7 g/GJ with an overall mean of 34.3 g/GJ.

These key changes to the methodology are designed to provide a more accurate and realistic estimation of the future impact of biomass uptake in the study areas of Dundee and Edinburgh.



3 Scenario development and air quality modelling

It was important to base this study on urban locations where concentrations of PM10 are close to or are exceeding the Air Quality Objective. Edinburgh and Dundee were selected on this basis. For example, the urban background sites, Edinburgh St Leonards and Dundee Broughty Ferry Road, both measured annual mean PM10 concentrations in 2006 of 20 μg m-3 (see Table 3.2). This is above the Scottish Air Quality Objective for annual mean PM10 of 18 μg m-3. As a comparison, the annual average PM10 concentrations for the rurally located monitoring sites at Auchencorth Moss and Glasgow Waulkmillglen Reservoir for 2006 were 7 μg m-3 and 15 μg m-3 respectively. This is well below the Scottish Air Quality Objective for annual mean PM10. The impact of any additional contribution to PM10 emissions in the urban areas is therefore of greater concern. The recent Air Quality Progress reports produced by both the City of Edinburgh and City of Dundee have also identified that further work, in the from of a Detailed Assessment, is required for PM10 across the city. The impact of biomass combustion on air quality in Edinburgh and Dundee was predicted using a dispersion model for a range of hypothetical emissions scenarios. The dispersion model and emission scenarios are described in this section and the results of the modelling are presented. The model was used to predict annual mean air quality ground level concentrations, which were then compared with relevant air quality objectives. The air quality objectives in Scotland for particulate matter were set out in the Air Quality Strategy 2007. They are:

• 18 μg m-3 as an annual mean for PM10 to be achieved by 31 December 2010 and maintained thereafter;

• 50 μg m-3 as a 24-hour mean for PM10 not to be exceeded on more than 7 times per year to be achieved by 31 December 2010 and maintained thereafter;

• 12 μg m-3 as an annual mean for PM2.5 to be achieved by 2020 and maintained thereafter; • a 15% reduction in PM2.5 annual mean concentrations at urban background locations between

2010 and 2020. The population-weighted mean has also been considered. The population-weighted mean concentration provides a measure of the average exposure of the population of Edinburgh and Dundee to particulate concentrations. It takes into account the spatial variability of the predicted concentrations and the distribution of the population throughout the cities. The concentration is predicted for each 1 km square of the city. Census data for 2001 is also available for each 1 km square. The population-weighted mean concentration is calculated by: 1) multiplying the concentration by the population for each 1 km square; 2) calculating the sum of these products over the whole city; 3) dividing the sum by the total population of the city.

3.1 Dispersion modelling The dispersion model ADMS4 was used to predict the contribution to annual mean particulate concentrations from biomass combustion sources throughout Edinburgh and Dundee. The ADMS4 model is well established and is widely used for air quality impact assessments for planning and permitting purposes for industrial, domestic, commercial and transport emission sources. Individual emission sources may be represented in the ADMS4 model as point sources, line sources, volume sources or area sources. Point sources were used to represent the emissions from individual boiler stacks. Volume sources, 10 m deep, were used to represent more diffuse emissions from large numbers of small domestic, commercial and industrial sources covering a wider area. A dispersion kernel modelling approach was used to apply the results of the ADMS4 modelling for these volume sources to a 1 km x 1 km grid of emissions.



The emissions from different categories of emission source (e.g. new housing developments, new business developments, schools) were modelled separately and the total impact was then calculated as the sum of the contributions from each source category. The model took into account hourly sequential meteorological data from Edinburgh Airport, 2006 and Leuchars, 2005. The Edinburgh Airport data was applied when modelling Edinburgh and the Leuchars data was applied when modelling Dundee because these were the closest sites to the two cities with adequate data for modelling. The modelling used the data with adequate data coverage for the most recent years available to us at the time of the work. A surface roughness of 1 m was used to represent the urban terrain throughout Edinburgh and Dundee. The ADMS4 model allows the differences in surface roughness between the cities and the airport meteorological sites to be taken into account. The surface roughness at Edinburgh Airport and Leuchars was assumed to be 0.1 m. The urban heat island effect was taken into account by limiting the Monin-Obukhov length to 30 m or more.

3.2 Background concentrations Biomass is only one of very many emission sources contributing to particulate concentrations. In order to assess the impact from biomass combustion on air quality it is necessary to determine both:

• the contribution to particulate concentrations from biomass combustion alone; and • the total concentration from all sources, for comparison with the air quality objectives.

In this study, the contribution from all sources other than biomass combustion is described as the background concentration. The contribution from the biomass combustion sources and the background concentration were determined separately. ADMS4 was used to calculate the contribution from the biomass combustion emissions. The annual mean background PM10 and PM2.5 concentration was then added to the modelled contributions from biomass sources to calculate the total background concentration. It is important to note that concentrations of PM10 and PM2.5 will be higher at locations closer to specific sources. This would need to be considered to determine the actual compliance with the air quality objectives. A wide range of sources contribute to background particulate matter concentrations in Edinburgh and Dundee. The method used for estimating the background concentration is described below.

3.2.1 Emissions from domestic, transport, commercial, industrial and agricultural sources

The background concentration throughout Edinburgh and Dundee for 2006, 2010 and 2020 was determined using the method developed by AEA Energy & Environment for the Environment Agency to enable the Agency to audit the contribution of regulated processes to pollution (Abbott, Stedman and Vincent, 2007a and 2007b). The approach uses two models: ADMS4 for modelling pollutant emissions from sources within 50 km and AEA’s acid deposition model, TRACK, for more distant sources. Estimates of area source emissions for 2006 were taken from the National Atmospheric Emission Inventory 1 km x 1 km for 2006. The inventory provides emissions estimates for each UNECE SNAP 97 source category for each 1 km square. The scaling factors for each SNAP source category are shown in Table 2.1.The emissions for each square for 2006 were scaled to 2010 and 2020 using historic and forecast emissions estimates from the NAEI.



Table 3.1: Year scaling factors applied to UNECE SNAP sector particulate matter emissions, with 2006 as base year.

Scaling factor with respect to 2006 emissions SNAP code Sector

2006 2010 2020

1 Combustion in energy 1 1.08 0.80 2 Residential and commercial 1 0.91 0.84 3 Combustion in industry 1 1.02 1.02 4 Production processes 1 0.93 0.98 5 Extraction/dist of fuels 6 Solvent 1 0.94 0.92 7 Road transport 1 0.89 0.53 8 Other transport and machines 1 0.93 0.92 9 Waste treatment 1 0.94 0.93

10 Agriculture 1 1.00 1.00 11 Other sources and sinks 1 1.00 1.00

The NAEI predicts that there are relatively high emissions from solid fuel combustion in Dundee, largely as an artefact of the methodology. Dundee City Council’s Review and Assessment Updating and Screening Assessment, 2003 reported that in 1994 2.4% of all housing tenures in Dundee were heated primarily by solid fuel/fuel oil. By 2004, it was predicted that the number of dwellings heated primarily by solid fuel/fuel oil would be significantly lower. It concluded that the PM10 contributions of domestic sources to air quality in 2004 would be negligible. The contribution from existing domestic sources to background particulate matter concentrations in Dundee was therefore set to zero.

3.2.2 Emissions from large point sources

Emissions data from large point sources within 50km of Dundee and Edinburgh were input into the model. Large point source emissions for 2005 were taken from the Environment Agency Pollution Inventory and the Scottish Pollution Release Inventory8. The large point source inventory included sources with emissions of greater than 500 tonnes per year of sulphur dioxide, 500 tonnes per year of oxides of nitrogen and 200 tonnes per year of PM10.

3.2.3 Emissions from other sources throughout UK and Europe

Estimates of European emissions were taken from the EMEP 50 x 50 km Expert emissions inventory for 2004, 2010 and 20209. The 2004 data was applied to 2006 without scaling - the inventory is used to calculate the contribution from long-range sources, which should be sufficiently small that year-to-year changes are unimportant.

3.2.4 Emissions of sulphur dioxide and nitrogen oxides

Sulphur dioxide reacts in the atmosphere to create particulate sulphate whilst nitrogen oxides react to create particulate nitrate. Sources of sulphur dioxide and nitrogen oxides throughout the UK and Europe are therefore important. Emissions for the 2010 and 2020 base cases for sulphur dioxide and the total fuel consumption for each coal-fired power station were obtained from the NAEI and were consistent with BERR’s Updated Energy Projections 30. Emissions of oxides of nitrogen for Drax, Eggborough and Longannet were taken from the National Emissions Reduction Plan (Statutory Instrument No. 2325, 2007). For other coal-fired power stations, the emissions of oxides of nitrogen were estimated based on the emission limits in the Large Combustion Plant Directive and typical flue

8 http://www.sepa.org.uk/SPRI/index.htm 9 http://www.emep-emissions.at/ceip/



gas flows of 8000 Nm3 at reference conditions per tonne of coal consumed. Emissions of PM10 for the future case were estimated based on emission factors calculated from the 2005 reported emissions and the coal consumed in each plant. A generic emission factor for PM10 specific to plant fitted with flue gas desulphurisation (FGD), calculated as the average of the 2005 emission factors for Drax, Ratcliffe and West Burton power stations, was applied to plants converting to FGD. The emissions from other large point sources were assumed to remain constant at 2005 levels. The 2020 case assumed that 4GW of new coal-fired plant would be in built and operating at 80 % load to replace old plant that has been scheduled to close. The new plant was assumed to be located close to the Thames Estuary (3.2 GW capacity) and in the East Midlands (0.8 GW capacity).

3.2.5 Coarse particulate matter from wind-blown dust, sea salt and other natural sources.

A component of 10.5 μg m-3 gravimetric was added to the modelled PM10 concentrations to take account of other sources (including natural sources such as wind –blown dust) that are not included in the model. This is consistent with assumptions made in Technical Guidance LAQM.TG(03) for Local Authority Review and Assessment. A component of 3.5 μg m-3 was added to modelled PM2.5 concentrations. There is considerable uncertainty about the contribution to particulate matter concentrations from natural sources and it is likely that the contribution will change with location. For example, the contributions in urban, suburban and rural areas may be different.

3.2.6 Verification of modelled concentrations against measured concentrations

Particulate matter (PM10) concentrations were measured at various sites throughout Scotland by Tapered Element Oscillating Microbalance (TEOM) in 2006. The data are reported in the Scotland Air Quality Data and Statistics Database10. The TEOM method differs from the gravimetric reference method specified in the Air Quality Regulations and a factor of 1.3 has been applied to convert the TEOM measurements to gravimetric. There were no valid measurements of annual mean PM10 concentrations using the gravimetric reference method at background sites in Scotland in 2006. It has been suggested that a factor smaller than 1.3 may be applicable in Scotland and this would lead to lower measured concentrations: however, the 1.3 factor is currently recommended for local authority review and assessment. The measured concentrations for 2006 from urban background, urban centre and rural sites were compared against the values derived from the model. The sites used were Aberdeen, Dundee Broughty Ferry Road, Edinburgh St Leonards, Glasgow Centre, Glasgow Waulkmillglen Reservoir and Perth. The data is presented in Table 3.2. The agreement between modelled and measured concentrations is satisfactory, with an error of 1.7 μg m-3 or less. Table 3.2 also shows, for comparison, concentrations provided by the background maps for 2005 used for Local Authority Review and Assessment11. These are lower than the measured and modelled concentrations and it was therefore concluded that the modelling approach used provides a better estimate of the measured concentrations. Nevertheless, the use of the model to predict the background concentrations introduces an element of uncertainty. Part of that uncertainty arises because the model predicts urban background concentrations at 1 km x 1 km resolution. Concentrations may vary within each 1 km square, particularly near to emission sources such as roads, where substantially higher concentrations are possible. The City of Edinburgh and Dundee City Councils reviewed measured PM10 concentrations in their most recent Local Authority Review and Assessment Progress Reviews and recommended that Detailed Assessments are carried out to determine the extent of potential exceedence of the air quality objectives in the two cities.

10 http://www.scottishairquality.co.uk/data_and_statistics.php 11 http://www.scottishairquality.co.uk/laqm.php?n_action=tools



Table 3.2: Comparison of measured and modelled PM10 concentrations.

Site Measured

concentration 2006 (μg m-3)

Modelled Concentration 2006 (μg m-3)

Difference (μg m-3)

Air quality archive

background data

Aberdeen 20.3 22.0 +1.7 15.5 Dundee Broughty Ferry Road 19.6 18.4 -1.2 13.8 Edinburgh St Leonards 20.0 18.7 -1.3 16.4 Glasgow Centre 21.3 22.5 +1.2 21.7 Glasgow Waulkmillglen Reservoir 14.9 15.3 +0.4 13.7 Perth 21.0 20.1 -0.9 14 There are other monitoring sites operated by local authorities in Scotland that are not included in the Scotland Air Quality Data and Statistics Database. The measurements from these sites have not been subjected to the same quality assurance procedures, but are likely to be valid measurements in most cases. The City of Edinburgh operates such a suburban background site at Currie High School. The annual mean PM10 concentration at this site in 2005 was 12.0 μg m-3 gravimetric equivalent (City of Edinburgh, 2006), which may be compared with the modelled concentration for 2006 of 16.7 μg m-3. This suggests that the model may overestimate concentrations in some suburban parts of Edinburgh. The model’s application in these areas may be considered to provide a conservative overestimate of PM10 concentrations. There were no valid measurements of annual mean PM2.5 concentrations at urban background sites in Scotland in 2006 and so no comparison of modelled and measured PM2.5 concentrations has been possible.

3.3 Overview of scenario development The assessment has considered five main scenarios. These are:

• Recent year, 2006; • Future year, 2010, business as usual without significant new biomass combustion; • Future year, 2010, including all planning applications with biomass combustion received by

the City of Edinburgh and Dundee City Councils; • Future year, 2020, business as usual without significant new biomass combustion; • Future year, 2020, with substantial estimated biomass combustion.

In order to assess the potential impact of biomass combustion on air quality in Edinburgh and Dundee in 2020, it is necessary to know where the biomass combustion will occur and the quantities of heat to be provided. The size and location of biomass combustion sources is not known for 2020. In this assessment, potential biomass installations have been identified in order to provide an estimation of the distribution of biomass combustion sources throughout the city. The potential installations include:

• housing developments in the local plans; • replacement of demolished housing or renovation; • existing housing; • schools; • business developments identified in the local plans; • retail developments identified in the local plans; • other institutions- universities, hospitals, barracks, prisons, government offices, etc.

The potential biomass installations have been identified by AEA Energy and Environment for the purposes of this assessment only. The inclusion in the assessment does not imply that the identified installations would be approved by the Scottish Government, City of Edinburgh Council, Dundee City



Council or the Scottish Environment Protection Agency. Nor does it imply that it will be practical, economic or desirable to install biomass combustion at these locations. The assumptions as to the most likely future installations have been made purely to assess the consequences for air quality of substantial biomass combustion. The purpose of this study is to assess whether the combined effect of many biomass installations would lead to substantial increases in particulate concentrations throughout areas of Dundee and Edinburgh. The maximum impact from each individual biomass installation will occur close to the point of discharge. This task implicitly assumes that the local impact of individual boilers can be adequately controlled by local authorities, planning authorities or by SEPA. The assessment assumes that the biomass installations will have similar emissions per unit of heat input to those tested, as the tested units were considered to be typical of current installations. Thus the assessment assumed that, on average, biomass combustion installations will emit between 20 and 60 g/GJ of particulate matter. The impact of individual biomass combustion appliances can be controlled by various measures. In this study we have assumed control of emissions is achieved via discharging through an elevated chimney stack. The maximum ground level concentration for a given emission rate depends on the stack height above ground and above nearby buildings. For this assessment, it has been assumed that the stack height will be sufficient to limit maximum ground concentrations to less than 1 μg m-3 for operation at capacity. Local authorities, as regulators, may set more or less stringent criteria depending on local circumstances. For example, they may require individual stacks to contribute considerably less than 1 μg m-3 if the background concentrations (including the influence of roads in the immediate vicinity) were already approaching the air quality objective. On the other hand, they may allow the individual plant to contribute more than 1 μg m-3 where there is no relevant exposure of members of the public. However, our experience suggests that the 1 μg m-3 criterion is likely to be protective of public exposure in most cases without requiring excessive stack heights. Draft Technical Guidance for Local Authority Review and Assessment TG(08) provides screening tools to allow local authorities to identify where there is a risk that an individual biomass combustion installation will lead to local exceedence of air quality objectives. The tools have been adapted in Appendix 3 to allow for Scottish meteorological conditions and the different air quality objectives in Scotland. The screening tools were used to estimate the stack heights required to limit maximum individual contribution to ground level concentrations to less than 1 μg m-3. The heat demand that could be met in 2020 by biomass at the identified installations has been estimated separately for Edinburgh and Dundee. The Scottish Government has set a target that 50% of the demand for electricity generated in Scotland must be met from renewable resources by 2020, with an interim milestone of 31% by 2011. There is currently no specific target for the fraction of heat demand (as opposed to electricity) to come from renewable sources. The Renewable Heat Group (Scottish Executive, 2008) recommended that the Scottish Government set a target for the minimum percentage of heat to come from a mix of renewable technologies by 2020. The Renewable Heat Group suggests that at least 20% of heat would need to come from renewable sources to achieve the EU target of 20% of energy consumed in the EU to come from renewable sources by 2020. This is currently being considered by the Scottish Government in the context of its forthcoming Renewable Energy Framework and the commitment to contribute to the EU target of 20% of all energy demand to be met from renewables by 2020. Table 3.3 shows the consumption of fossil fuels and electricity in Dundee, Edinburgh and Scotland for 2005 (BERR, 2008). Most of the electricity is used for purposes other than heating such as lighting, cooking and running appliances. It has been assumed that 28% of domestic electricity and 17.7% of commercial electricity is used for space and water heating12,13. It is thus estimated that the total annual heat demand in 2005 was 11.07 PJ in Dundee and 24.7 PJ in Edinburgh. It is anticipated that the heat demand will change in future years as the result of energy efficiency measures (e.g. increased insulation and more efficient boilers in the existing buildings), the replacement of demolished buildings with more thermally efficient buildings and as a result of new residential, commercial and retail

12 http://stats.berr.gov.uk/energystats/ecuk3_7.xls 13 http://stats.berr.gov.uk/energystats/ecuk5_5.xls



developments. The change in heat demand as the result of these changes is considered for Dundee and Edinburgh in Sections 3.4 and 3.5 respectively. Table 3.3: Annual heat demand for the whole of Scotland and for Dundee and Edinburgh in

2005 in terajoules (TJ).

Area Scotland Dundee Edinburgh

Industry & Commercial 195193 3608 9986 Fossil fuels

Domestic 143362 5607 12516

Industry & Commercial 61610 1784 6145 Electricity

Domestic 44609 1452 3710

Industry & Commercial 10905 316 1088 Electricity used for heating Domestic 12491 407 1039

Industry & Commercial 206098 3924 11074

Domestic 155853 6013 13554 Total heat

Renewables and waste* 15796 1133 73

Total 377747 11070 24701 * The contribution for renewables and waste has been included within the total heat demand. A substantial part of the waste in Dundee is burned in an Energy from Waste plant. Although the plant supplies electricity to the grid, it does not currently supply heat to Dundee consumers.



3.4 Dundee modelling This section details the scenario development for Dundee for 2010 and 2020 and presents the results for the five modelling scenarios. Figure 3.1 shows the boundaries of the City of Dundee, which are presented in each of the figures in this section. The major road network is included on Figure 3.1 to provide a point of reference.

Figure 3.1: Map of the City of Dundee showing the area modelled.

3.4.1 Recent year, 2006: Dundee

Figure 3.2 shows the modelled annual mean background PM10 concentration for a recent year, 2006. The modelled concentration in Dundee is less than the air quality objective for 2010 of 18 μg m-3 for much of the Council area. The modelled concentrations exceeded the objective for 2010 in parts of the city centre and some industrial areas.



Modelled PM10 concentration, ug/m3 gravimetric

<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.2: Modelled annual mean PM10 concentrations at background locations in Dundee, 2006.

The National Atmospheric Emissions Inventory allocates relatively high emissions to some industrial areas based on employment statistics and this results in the prediction of relatively high particulate matter concentrations in the immediate vicinity of the industrial areas. However, the inventory does not contain site-specific information relating to the factories and so the predicted high concentrations may be considered to be an artefact of the inventory. Dundee City Council has assessed industrial emissions as part of the Local Authority Air Quality Review and Assessment process and concluded that detailed assessment was not required (Dundee City Council, 2003). It is not likely that that the objective will be exceeded near to these industrial areas. The predicted number of exceedences of the 24 hour limit value for PM10 of 50 μg m-3 was calculated from the annual mean value using the statistical relationship presented in Technical Guidance LAQM.TG(03) for Local Authority Review and Assessment. Less than 2 exceedences were predicted throughout Dundee except close to the industrial estate at Denhead of Gray. The model predicted that the objective of less than 7 exceedences would be met at background locations throughout the city. Figure 3.3 shows the predicted annual mean PM2.5 concentration at background locations throughout Dundee in 2006. The predicted concentration was less than the objective of 12 μg m-3 at background locations throughout the city.



PM2.5 concentration, ug/m3

<8

8-10

10-12

12-14

14-16

>16

Figure 3.3: Modelled annual mean background PM2.5 concentrations in Dundee, 2006.

3.4.2 Business as usual, 2010: Dundee

Figure 3.4 shows the modelled annual mean PM10 concentration for the business as usual case for 2010. The modelled concentration in Dundee is less than the air quality objective for 2010 of 18 μg m3 at background locations throughout the Council area.

Modelled PM10 concentration, ug/m3 gravimetric<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.4: Modelled annual mean PM10 concentrations at background locations in Dundee, business as usual, 2010.

The predicted number of exceedences of the 24 hour limit value for PM10 of 50 μg m-3 was calculated from the annual mean value using the statistical relationship presented in Technical Guidance LAQM.TG(03) for Local Authority Review and Assessment. The predicted number of exceedences is fewer than two at all background locations throughout Dundee, compared to the objective for 2010 of fewer than seven exceedences.



Figure 3.5 shows the predicted annual average PM2.5 concentrations for Dundee. The predicted concentration is less than the objective of 12 μg m-3 for 2010 at background locations throughout the city. The PM2.5 population-weighted mean concentration for Dundee was 8.54 μg m-3.

PM2.5 concentration, ug/m3<8

8-10

10-12

12-14

14-16

>16

Figure 3.5: Modelled annual mean background PM2.5 concentrations in Dundee, business as usual. 2010.



3.4.3 Future year 2010, with proposed biomass: Dundee

In order to assess the potential impact of biomass combustion on air quality in Dundee in 2010, it is necessary to know where the biomass combustion will occur and the quantities of heat to be provided. Dundee City Council has received planning applications for the installation of biomass combustion units for two developments: an office development and a Part B regulated industrial process14. Dundee University is also considering a biomass boiler installation for the Fulton Building. For the purposes of this modelling scenario Dundee City Council has identified various other sites that it considers have the most potential for biomass heating. It is possible that biomass heating could be operating by 2010 at these sites. However, given the timescales involved, it is not likely that many other significant new installations will be in operation by 2010. The 2010 scenario assessed in this study assumes that all potential biomass combustion sources identified by the Council will be in operation. The identified sites are listed in Table 3.4.

Table 3.4: Potential biomass installations for 2010 in Dundee.

Name Category Easting (m)

Northing (m) Estimated Load

Harris Academy Secondary School 337919 729774 700kW Braeview Academy Secondary School 343751 733882 700kW

Craigie High Secondary School 343304 731593 700kW

Barnhill Primary School 347429 732167 300kW

Eastern Primary School 346592 730981 300kW

Lawside Academy Secondary School 338354 733106 700kW

St Saviour's High Secondary School 343574 732804 700kW

Wallacetown Health Centre Planning Application 340906 731213 ?

Office development Planning Application 335008 731351 130 - 250kW

Dundee University, Fulton Building Planning Application 339718 730071 2MW

Part B industrial process Planning Application 337149 732974 1.75MW output/ 2.2MW nominal input rating

Broughty Ferry Library Public Library 346275 731029 50kW No information was available on the emission discharge arrangements or building dimensions for the proposed developments except for the Part B industrial process site. Table 3.5 shows the modelled point source discharge characteristics for each of the modelled developments. The average heat demand for each boiler unit (for the Part B process) was estimated assuming 30% utilisation: the generating unit at the Fulton building was assumed to run at capacity at all times. The average rate of emission was estimated based on emission factors of 20 g/GJ and 60 g/GJ representing the range of current boiler performance (except for the Part B process) based on the range of boilers tested in this study. Discharge flowrates at capacity were then estimated assuming a theoretical air requirement of 0.3 kg air per MJ (Chemical Engineers Handbook (Perry and Green, 2007)), 6% excess air and discharge at 100oC. Stack diameters were then selected from the set 0.1 m, 0.2 m, 0.5 m and 1 m based on the natural draught flowrates used in the development of the nomographs (Appendix 3). Stack heights above ground were then estimated using the nomographs with the aim of limiting the maximum local contribution to annual mean particulate matter concentrations from each individual plant operating at capacity to less than 1 μg m-3. It was assumed that each stack would discharge above a rectangular building 10 m high and 30 m square.

14 Part B processes are lesser polluting industrial processes that are regulated by Local Authorities for their emissions to air.



Table 3.5. Modelled point source discharge characteristics for 2010 biomass installations.

Location Particulate emission rate (g/s)

Stack height (m)

Site Easting Northing 20 g/GJ 60 g/GJ

Diameter (m)

Discharge velocity (m s-1) 20

(g/GJ)60

(g/GJ)

Harris Academy 337919 729774 0.0042 0.0126 0.5 2.57 15 20

Braeview Academy 343751 733882 0.0042 0.0126 0.5 2.57 15 20

Craigie High 343304 731593 0.0042 0.0126 0.5 2.57 15 20

Barnhill 347429 732167 0.0018 0.0054 0.5 1.10 12 15

Eastern 346592 730981 0.0018 0.0054 0.5 1.10 12 15

Lawside Academy 338354 733106 0.0018 0.0054 0.5 1.10 12 15

St Saviour's High 343574 732804 0.0042 0.0126 0.5 2.57 15 20

Wallacetown Health Centre 340906 731213 0.0012 0.0036 0.5 0.73 11 14

Office development** 335008 731351 0.0015 0.0045 0.5 0.92 12 15

Dundee University Fulton Building 339718 730071 0.0400 0.1200 1 5.50 18 24

Part B industrial process*

337149 732974 0.21 0.21 0.4 15.6 24 24

Broughty Ferry Library 346275 731029 0.0003 0.0009 0.2 1.15 11 12 * Planning Application No DCC No. 08/00587/FUL. ** The emissions and stack discharge characteristics modelled here differ from those proposed by the developers. The modelling presented here is illustrative only and does not take into account all the factors potentially affecting the dispersion of pollutants. Figure 3.6 shows the predicted contribution from the identified biomass installations to annual mean particulate matter concentrations for boilers with an emission factor of 60 g/GJ. The predicted contribution is less than 0.1 μg m-3 at most locations except close to the proposed boilers. The maximum predicted ground level concentration was 0.7 μg m-3 close to the proposed Part B process plant.



Contribution, ug/m3<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.6: Modelled contribution to particulate matter concentrations from identified biomass

installations in Dundee in 2010 assuming an emission factor of 60 g/GJ. The contribution from the proposed developments has been added to the background concentrations for 2010. Figure 3.7 shows the resulting total PM10 concentration for biomass emissions at 60 g/GJ. The concentrations are slightly increased compared with the business as usual case, but the modelled concentration in Dundee remains less than the air quality objective for 2010 of 18 μg m-3 at background locations throughout the Council area. The predicted number of exceedences of the 24-hour PM10 objective remains fewer than two at all background locations throughout Dundee, compared to the objective of less than seven exceedences. The total PM10 concentrations for biomass emissions at 20 g/GJ were indistinguishable from the business as usual case for 2010 and hence are not plotted in this report.


14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.7: Modelled annual mean background PM10 concentrations in Dundee, 2010, including proposed new developments with emission factor 60 g/GJ.



Figure 3.8 shows the predicted total PM2.5 concentrations for biomass emissions at 60 g/GJ. The predicted concentrations are slightly greater than for the business as usual case, but remain below the objective of 12 μg m-3 at background locations throughout the city. The predicted PM2.5 population–weighted mean concentration for Dundee was less than 0.01 μg m-3 greater than for the business as usual case. The total PM2.5 concentrations for biomass emissions at 20 g/GJ were indistinguishable from the business as usual case for 2010 and hence are not plotted in this report.


8-10

10-12

12-14

14-16

>16

Figure 3.8: Modelled annual mean background PM2.5 concentrations in Dundee, 2010,

including proposed new developments with emission factor 60 g/GJ.

3.4.4 Business as usual, 2020: Dundee

Figure 3.9 shows the modelled annual mean PM10 concentration for the business as usual case for 2020. The modelled concentration in Dundee is less than the air quality objective for 2010 of 18 μgm-3 at background locations throughout the Council area.


14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.9: Modelled annual mean PM10 concentrations at background locations in Dundee, business as usual, 2020.



The predicted number of exceedences of the 24 hour limit value for PM10 of 50 μg m-3 was calculated from the annual mean value using the statistical relationship presented in Technical Guidance LAQM.TG(03) for Local Authority Review and Assessment. The predicted number of exceedences is fewer than two at all background locations throughout Dundee, compared to the objective for 2010 of fewer than seven exceedences. Figure 3.10 shows the predicted annual average PM2.5 concentrations for Dundee. The predicted concentration is less than the objective of 12 μg m-3 for 2020 at background locations throughout the city. The predicted population-weighted mean concentration for Dundee was 8.40 μg m-3, approximately 2% less than the equivalent concentration for 2010. It will be difficult to achieve substantial exposure reduction in Dundee between 2010 and 2020 without additional measures to control PM2.5 emissions.


8-10

10-12

12-14

14-16

>16

Figure 3.10: Modelled annual mean background PM2.5 concentrations in Dundee, business as usual, 2020.

3.4.5 Future year 2020, with substantial biomass combustion: Dundee

The scenario for 2020, with substantial biomass combustion, has been derived by identifying potential sources from a number of groups of developments. These groups are as follows:

• Future housing developments already identified • Replacement of demolished housing • Modification at existing housing • Schools • Business, retails and institutional developments.

For most of these development groups, the modeled contributions from biomass with an emission factor of 20g/GJ was less than 0.1 μgm-3 throughout the modeled area and hence, could not be shown on a concentration map. For the total contribution from all groups, concentration maps for both 20g/GJ and 60g/GJ emission factors are provided.

Housing developments identified in the local plans

The Dundee and Angus Housing Land Audit 2007 (Angus Council and Dundee City Council, 2007) identified a mix of greenfield and brownfield sites throughout the city. The City Council provided up-to-date data on the status of these sites including the total number of dwellings allocated to each site and the number of dwellings for which construction has started or been completed. It has been assumed here that dwellings for which construction had already started would not be heated by biomass combustion but that all of the remaining 4527 dwellings would be heated by biomass combustion.



The total heat demand for these new dwellings has been estimated based on an annual heat demand of 30 GJ per household (see discussion below for Edinburgh, Section 3.5.5). The estimated total heat demand was 136 TJ. This is approximately 1.2% of the current heat demand in Dundee.

The Local Audit indicates that most of the new developments will have relatively low housing densities. It is likely that each house would be supplied with an individual boiler. The emissions have therefore been modelled as 1 km x 1 km volume sources, 10 m deep. Modelling was carried out assuming that the installed boilers have emissions factors of 20 g/GJ and 60 g/GJ, representing the range of emission factors measured in recently installed boilers.

Figure 3.11 shows the contribution to particulate concentrations from the new developments with biomass boilers emitting 60 g/GJ. The predicted impact is restricted to areas close to the new developments. The predicted contribution to particulate matter concentrations is less than 0.1 μg m-3 throughout most of Dundee, increasing to 0.2-0.5 μg m-3 near the largest developments. For boilers emitting 20 g/GJ, the contribution is a factor of three lower and is less than 0.2 μg m-3 throughout the city.


0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.11: Modelled contribution to particulate matter concentrations from new housing developments in Dundee in 2020 assuming an emission factor of 60 g/GJ.

Replacement of demolished housing

Table 3.3 indicates that the current domestic heat demand satisfied by fossils fuels and electricity in Dundee is 6013 TJ per annum. Part of the existing housing will be demolished or substantially renovated and replaced by housing meeting new building regulations. The Dundee and Angus Structure Plan 2001-2016 (Dundee City Council, 2002), Report of Survey reports plans to demolish 2490 dwellings out of a housing stock of 66400 households (3.9%) but notes that further demolitions will undoubtedly come forward over the Structure Plan period, although considerable uncertainty exists over the extent of this. It has been assumed here that 5% of the housing stock is replaced by 2020. The energy demands of the new houses will be less than the existing houses. Typical annual heat demands for UK households for space and water heating are 63.8 GJ per household15 compared to 30 GJ assumed here for new household heat demands. The overall heat demand will be reduced by 159 TJ per annum if demolished or renovated houses are replaced on a like for like basis. The annual heat requirement for the replacement properties will be 141 TJ, approximately 1.3% of Dundee’s current heat demand. If the heat demand for the new properties is met by biomass boilers

15 http://stats.berr.gov.uk/energystats/ecuk3_3.xls http://stats.berr.gov.uk/energystats/ecuk3_6.xls



with particulate emissions of 20 g/GJ of heat provided then the annual emission would be 2.83 tonnes. For an emission factor of 60 g/GJ, the emission will be three times greater. No information was available about where demolition and renovation will take place. The particulate emissions have therefore been allocated across the city in proportion to population based on 2001 census data. The contribution to annual mean concentrations from this source is predicted to be less than 0.1 μgm-3 for appliances with emission factors of 20 g/GJ. Figure 3.12 shows the predicted contribution from replacement houses fitted with biomass boilers with emission factors of 60 g/GJ. The predicted contribution remains less than 0.2 μg m-3 throughout Dundee, with the highest concentrations in the city centre.


0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.12: Modelled contribution to particulate matter concentrations from replacement housing in Dundee in 2020 assuming an emission factor of 60 g/GJ.

Existing houses

Houses in the least densely populated areas of Dundee have the greatest potential to install biomass heating. Tenement blocks in the more densely populated areas have less potential for conversion. In this study, we have assessed the potential for conversion to biomass on the basis of population density throughout Dundee in 2001 as follows:

Less than 1000 inhabitants per km2 10% Between 1000 and 4000 inhabitants per km2 5% More than 4000 inhabitants per km2 1%

Overall, it is estimated that this would lead to conversion of 4.1% of the existing housing stock. It has also been assumed that biomass would then meet 4.1% of the current domestic heating demand for the city (244.6 TJ per annum) (2.2% of Dundee’s total heat demand). Assuming a particulate matter emission factor of 20 g/GJ for these installations provides an estimated annual emission of 4.89 tonnes. For an emission factor of 60 g/GJ, the emission will be three times greater. The contribution to annual mean concentrations from this source is predicted to be less than 0.1 μgm-3 for appliances with emission factors of 20 g/GJ. Figure 3.13 shows the predicted contribution from existing houses fitted with biomass boilers with emission factors of 60 g/GJ. The predicted contribution remains less than 0.2 μg m-3 throughout Dundee, with the highest concentrations in the suburbs surrounding the city centre.



Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.13: Modelled contribution to particulate matter concentrations from biomass installations as replacement heating in existing housing in 2020 in Dundee assuming an emission factor of 60 g/GJ.

Schools

The gross internal floor area of primary schools in Dundee is 110629 m2: the floor area of secondary schools is 116973 m2. There were 9720 primary school pupils and 8026 secondary school pupils in 200716. Service sector fuel use for space and water heating in 2005 was typically 5327 GJ gross per hectare of floor space (BERR data). The annual heat demand for primary schools is thus 58.9 TJ; for secondary schools the annual heat demand is estimated to be 62.3 TJ. If this heat demand is met by biomass combustion with particulate emission factor of 20 g/GJ the annual emission from schools would be 2.4 tonnes. For an emission factor of 60 g/GJ the emission is three times greater. The total emissions have been allocated to each school in Dundee in proportion to the number of pupils. Each of the primary school boiler discharges was modelled as a point source with stack diameter 0.5 m and stack height 12 m above ground next to a rectangular building 10 m high and 30 m square. The discharge temperature was assumed to be 100oC and the discharge velocity was 1.4 m s-1. These conditions broadly correspond to a 400 kW boiler. Each of the secondary school boiler discharges was modelled as a point source with stack diameter 0.5 m and stack height 14 m above ground next to a rectangular building 10 m high and 30 m square. The discharge temperature was assumed to be 100oC and the discharge velocity was 2.6 m s-1. These conditions broadly correspond to a 700 kW boiler. The stack heights were selected to ensure that the contribution from the individual boilers did not exceed 1 μg m-3 in the immediate vicinity of the boilers. In practice, the stack heights will be selected for each school on a case-by-case basis. Figure 3.14 shows the modelled contribution to particulate matter concentrations from biomass installations in all schools in Dundee assuming an emission factor of 60 g/GJ. The predicted contribution is less than 0.1 μg m-3 over most of the city, with higher concentrations in the vicinity of the schools. The maximum predicted contribution was less than 0.5 μg m-3. If the boilers operated with an emission factor of 20 g/GJ, the maximum predicted contribution was less than 0.2 μg m-3 and the predicted contribution over most of the city was less than 0.1 μg m-3.

16 http://www.scotland.gov.uk/Topics/Statistics/Browse/School-Education/TrendSchoolEstate (Scottish Government Statistics)



Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.14: Modelled contribution to particulate matter concentrations from biomass installations in all schools in 2020 in Dundee assuming an emission factor of 60 g/GJ.

Business, retail and institutional developments

The Dundee Local Plan identifies the main areas allocated for economic development in Dundee. High amenity economic development areas identified include the Dundee Technology Park, the Ninewells Medi-Park, the Hawkhill Technopole and the Railyards Digital Media Park. In addition, the Local Plan allocates a large high amenity strategic site within the Dundee Western Gateway area and further areas at the Claverhouse Business Park, the Linlathen Economic Development site and at the gas holder site in Dock Street. The Local Plan identifies areas for retail development at the gas holder site on Dock Street, at the Linlathen High School site and on Dura Street. The Local Plan considers further development at the sites of major institutions such as NHS Trusts and higher and further education institutions. The Dundee Central Waterfront Masterplan provides the basis for extensive development of the waterfront and the integration of the waterfront with the city centre. Current developments are in progress or have been recently completed at Gellaty Street, City Quay, Seabraes Mills, Merchant’s Quay, Marketgait, the former Homebase site, Seabraes and Dundee One. Two development sites have been advertised at Yeoman Shore and at Seabraes Yards, which together will provide 36,000 m2 of mixed-use space. Table 3.6 lists the business, retail and institutional development areas taken into account in this assessment. The area of the development was in most cases taken from the Local Plan or estimated from the Local Plan map. Floor areas for each development were then estimated on the basis of 2-storey buildings covering 50 % of the land area. Service sector fuel use for space and water heating in 2005 was typically 5327 GJ gross per hectare of floor space (BERR data). The heat demands have been estimated on this basis in Table 3.6. The total heat demand for the Waterfront area was estimated to be 43 TJ on the basis of space at the two current development sites and allowing for further development at other sites in the area. The total heat demand calculated for all these developments is 1233 TJ, corresponding to 11.1% of Dundee’s current heat demand. It has been assumed here as the maximum impact case that all the heat demand will be met by biomass combustion. Table 3.6 also shows the annual particulate emission for each development based on a particulate emission factor of 20 g/GJ. For developments with annual heat demands greater than 30 TJ, it has been assumed that the heat is supplied by biomass CHP with 50% thermal efficiency. It has



also been assumed that the electricity generated is exported to the grid, rather than used for electrical heating within the development.

Table 3.6: Business, retail and institutional developments in Dundee.

Site Area Easting (m)

Northing (m)

Floorspace (m2)

Heat demand

(TJ)

Particulate emission

(kg/year @20 g/GJ)

Western Gateway 50 333300 730800 500000 266 10654

Ninewells MediPark 12 335500 730600 120000 64 2557

Dundee Technology Park 40 334800 730900 400000 213 8523

DTP2 20 334800 731400 200000 107 4262

Digital media Park 5 339487 729523 50000 27 533

Hawkhill Technopole 3 339143 729957 30000 16 320

Claverhouse Business Park 20 342500 734500 200000 107 4262

Linlathen 50 346500 733500 500000 266 10654

Gasholder site 5 341500 731500 50000 27 533

Gasholder retail 2 341200 731500 20000 11 213

Linlathen High School 0.4 346500 733500 4000 2 43

Dura street 0.13 341051 731471 1300 1 14

Medical School 336000 730400 43 1703

University 339500 730500 43 1703

Waterfront 340400 729800 43 1703

Table 3.7 summarises the modelled discharge characteristics for the discharge points for the boilers installed at each of the development areas. The thermal capacity of each unit was estimated assuming 30% utilisation for boiler units and 45% utilisation for CHP units. Discharge flowrates at capacity were then estimated assuming a theoretical air requirement of 0.3 kg air per MJ (Chemical Engineers Handbook), 6% excess air and discharge at 100oC. Stack diameters were then selected from the set {0.1 m, 0.2 m, 0.5 m and 1 m} based on the natural draught flowrates used in the development of the nomographs (Appendix 3). It was assumed that large installations would have multiple stacks with 1 metre stack diameter. Stack heights above ground were then estimated using the nomographs with the aim of limiting the maximum local contribution to annual mean particulate matter concentrations from each individual development to less than 1 μg m-3. It was assumed that each stack would discharge above a rectangular building 10 m high and 30 m square.



Table 3.7: Modelled discharge characteristics for business, retail and institutional developments in Dundee.

Site Average

emission rate (g/s @

20 g/GJ)

Maximum emission

rate (g/s@

20 g/GJ)

Thermal capacity

(MW) Diameter No.

units Discharge velocity

Stack height, m for

20g/GJ emissions

Stack height, m for 60g/GJ emissions

Western Gateway 0.3378 0.7507 37.5 1 8 4.30 40 50

Ninewells MediPark 0.0811 0.1802 9.0 1 1 8.25 24 37

Dundee Technology Park 0.2703 0.6006 30.0 1 6 4.58 38 50

DTP2 0.1351 0.3003 15.0 1 3 4.58 29 42

Digital media Park 0.0169 0.0563 2.8 1 1 2.58 19 25

Hawkhill Technopole 0.0101 0.0338 1.7 1 1 1.55 17 20

Claverhouse Business Park 0.1351 0.3003 15.0 1 3 4.58 29 42

Linlathen 0.3378 0.7507 37.5 1 8 4.30 40 50

Gasholder site 0.0169 0.0563 2.8 1 1 2.58 19 25

Gasholder retail 0.0068 0.0225 1.1 1 1 1.03 14 18

Linlathen High School 0.0014 0.0045 0.2 0.5 1 0.83 12 14

Dura street 0.0004 0.0015 0.1 0.2 1 1.68 11 12

Medical School 0.0540 0.1200 6.0 1 1 5.50 21 32

University 0.0540 0.1200 6.0 1 1 5.50 21 32

Waterfront 0.0540 0.1200 6.0 1 1 5.50 21 32

Figure 3.15 shows the modelled contribution from business, retail and institutional developments in Dundee to particulate matter concentrations for an emission factor of 20 g/GJ. The modelled contribution is less than 0.1 μg m-3 over most of Dundee, with higher contributions up to 1 μg m-3 in the immediate vicinity of the Western Gateway and Dundee Technology Park. Figure 3.16 shows the contribution for an emission factor of 60 g/GJ. The modelled contribution exceeds 0.2 μg m-3 over a substantial part of Dundee, with concentrations up to 2 μg m-3 in the immediate vicinity of the Western Gateway and Dundee Technology Park.



Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.15: Modelled contribution to particulate matter concentrations from biomass installations in business, retail and institutional developments in 2020 in Dundee assuming an emission factor of 20 g/GJ.

Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.16: Modelled contribution to particulate matter concentrations from biomass

installations in business, retail and institutional developments in 2020 in Dundee assuming an emission factor of 60 g/GJ.

Total contributions from biomass combustion to particulate concentrations

Figure 3.17 shows the total contribution from biomass installed in new housing developments, rebuilt or renovated houses, a proportion of existing houses, all schools, new business developments, new retail developments and various institutions assuming that the emission factor is 20 g/GJ. Figure 3.17 shows that it is predicted that annual mean particulate concentrations will increase by 0.2-0.5 μg m-3 in large parts of the city.



Figure 3.18 shows the total contribution to annual mean particulate concentrations if the boilers operated with an emission factor of 60 g/GJ. It is predicted that annual mean particulate concentrations will increase by 0.5-1.0 μg m-3 in large parts of the city.


0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.17: Modelled contribution to particulate matter concentrations from all modelled biomass installations in 2020 in Dundee assuming an emission factor of 20 g/GJ.


0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.18: Modelled contribution to particulate matter concentrations from all modelled biomass installations in 2020 in Dundee assuming an emission factor of 60 g/GJ.



Total concentrations

Figure 3.19 shows the sum of the modelled contributions from biomass combustion and the background PM10 concentration for biomass combustion with a 20 g/GJ emission factor whilst Figure 3.20 shows the sum of the modelled contributions from biomass combustion and the background PM10 concentration for biomass combustion with a 60g/GJ emission factor. The predicted concentration is less than the objective for 2010 of 18 μg m-3 at all locations for both emission factors. With the 60g/GJ factor there are fewer than two predicted exceedences of the 24-hour limit value of 50 μg m-3 in the city centre compared to the objective of less than 7 exceedences.


14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.19: Modelled annual mean PM10 concentrations at background locations in Dundee, 2020, with modelled biomass installations emitting 20 g/GJ.


<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.20: Modelled annual mean PM10 concentrations at background locations in Dundee, 2020, with modelled biomass installations emitting 60 g/GJ.



Figure 3.21 shows the predicted annual average PM2.5 concentrations for 2020 including biomass combustion with emission factors of 20 g/GJ whilst Figure 3.22 shows the predicted annual average PM2.5 concentrations for 2020 including biomass combustion with emission factors of 60 g/GJ.. The predicted concentration is less than the objective of 12 μg m-3 for 2010 at background locations throughout the city for both scenarios. The predicted population-weighted mean concentration was 8.89 μg m-3 with biomass combustion with emission factors of 60 g/GJ and 8.53 μg m-3 for an emission factor of 20 g/GJ. These concentrations may be compared with the business as usual concentration of 8.40 μg m-3 for 2020 and 8.54 μg m-3 for 2010. Hence, compared to the target 15% exposure reduction for PM2.5, there is a 2% reduction with no biomass, no reduction with biomass with 20g/GJ emission rate and a 4% increase with biomass with a 60 g/GJ emission rate.


8-10

10-12

12-14

14-16

>16

Figure 3.21: Modelled annual mean background PM2.5 concentrations in Dundee, 2020, with

modelled biomass installations emitting 20 g/GJ.


8-10

10-12

12-14

14-16

>16

Figure 3.22: Modelled annual mean background PM2.5 concentrations in Dundee, 2020, with modelled biomass installations emitting 60 g/GJ.



3.4.6 Summary for Dundee

Modelled annual mean PM10 concentrations in Dundee for 2006 were generally less than the objective for 2010 of 18 μg m-3, except in parts of the city centre and some industrial areas. By 2010, the model predicts that the annual mean concentration will be less than the objective throughout the city in the absence of substantial biomass combustion. Further small reductions in PM10 concentrations are predicted by 2020. The Dundee City Council has received planning applications for the installation of biomass combustion units for various developments. The potential impact of these biomass installations for 2010 is small provided that the localised impacts are controlled to limit the maximum contribution to ground concentrations to less than 1 μg m-3 for operation at capacity17. Predicted contributions to particulate concentrations are generally less than 0.1 μg m-3 except in the immediate vicinity of the proposed installations. The size and location of biomass combustion sources is not known for 2020. In this assessment, potential biomass installations have been identified in order to provide an assessment of the distribution of biomass combustion sources throughout the city.

The current heat demand for Dundee of 11070 TJ per annum will increase as the result of the identified new developments, demolition and renovation to 12280 TJ. If biomass combustion was installed in each of the identified new developments, in some of the existing housing and in schools and other institutions identified, it is expected that it would provide a total of 1876 TJ of heat. This is 15.3% of the projected total heat demand. In practice, it will not be possible to install biomass heating in all the sites identified. In addition, there will be other sites, not yet identified where biomass heating can be readily installed. Nevertheless, the analysis provides the basis for assessing the distribution of biomass combustion sources throughout the city and the effect on air quality of widespread adoption of biomass combustion. To estimate the impact of biomass combustion at different uptake rates of biomass heating, the modelling outputs presented here will scale in proportion to the fraction of the heat demand met by biomass. The combined effect of the potential biomass installations for 2020 depends on the emission rate and the design of the discharge stacks. Model runs were carried out assuming emission factors of 20 and 60 g/GJ representing the range of emissions measured in plant recently installed in Scotland. Chimney heights for business, retail and institutional developments have been assigned to limit the individual ground level contributions from each development to annual mean concentrations to less than 1 μg m-3 for plant operating continuously at capacity. For the 20g/GJ emission factor, the effect of biomass combustion is to increase annual mean particulate matter concentrations across much of the city centre by 0.2-0.5 μg m-3. This equates to 1 to 4% of the modelled PM10 concentration arising from all other sources in these city centre areas. For biomass combustion installations operating with emission factors of 60 g/GJ, the particulate concentrations are predicted to increase by 0.5-1.0 μg m-3

across large parts of the city. This is equivalent to 4 to 7% of the modelled PM10 concentration arising from all other sources in these city centre areas. The model indicates that the air quality objective of 18 μg m-3 as an annual mean for PM10 will be met at background locations throughout the city in 2010 and 2020 for all modelled scenarios, with and without biomass combustion. The model predictions for 2010 and 2020 indicate that the daily mean objective for PM10 of less than 7 exceedences per year of the limit value of 50 μg m-3 will be met at background locations throughout the city for all modelled scenarios, with and without biomass combustion. The model predicts urban background concentrations at 1 km x 1 km resolution. Concentrations will vary within each 1 km square and may be substantially higher close to emission sources such as roads. At these locations, the objective may not be achieved: indeed, for some small areas, a very small increase associated with biomass combustion will be sufficient to cause exceedence of the objective where it would not otherwise occur. Dundee City Council’s most recent

17 In this study, it has been assumed that this will be achieved by use of an appropriate chimney height. However, other measures, such as, additional emission abatement control systems, fuel type and boiler selection could be used to achieve the same outcome.



Local Air Quality review and Assessment Progress Report indicated that there was a risk that the air quality objective would not be achieved and recommended that a Detailed Assessment be carried out. The predicted annual average PM2.5 concentrations for 2010 and 2020 are less than the objective for 2020 of 12 μg m-3 at background locations throughout Dundee for all scenarios, with and without biomass combustion. Compared to the exposure reduction target of 15% by 2020, for PM2.5, there is a 2% reduction with no biomass, no reduction with biomass with 20g/GJ emission rate and a 4% increase with biomass with a 60 g/GJ emission rate. Hence, the modelling scenarios without biomass installations indicate that it will already be difficult to achieve the 15% exposure reduction objective between 2010 and 2020. Based on the assumption in this study, the combined impact of widespread uptake of biomass installations could increase the difficulty in achieving this target, taking into account emissions from the main existing sources. Controlling emissions from biomass boilers to the lower range used in this study will minimise this impact and additional controls could be explored.



3.5 Edinburgh modelling This section details the scenario development for Edinburgh for 2010 and 2020 and presents the results for the five modelling scenarios. Figure 3.23 shows the boundaries of the city, which are presented in each of the figures in this section. The major road network is included on Figure 3.21 to provide a point of reference.

Fig. 3.23: Map of the City of Edinburgh showing the area modelled.

3.5.1 Recent year, 2006: Edinburgh

Figure 3.24 shows the modelled annual mean PM10 concentration for a recent year, 2006. The modelled concentration in Edinburgh is less than the air quality objective for 2010 of 18 μg m-3 for much of the Council area. The modelled concentrations exceeded the objective for 2010 in parts of the city centre, Newbridge and Queensferry and close to quarries in the rural west of Edinburgh. The National Atmospheric Emissions Inventory allocates relatively high emissions to quarry operations and this results in the prediction of relatively high particulate matter concentrations in the immediate vicinity of the quarries. However, the inventory does not contain site-specific information relating to the individual quarries and so the predicted high concentrations may be considered to be an artefact of the inventory. The City of Edinburgh Council has assessed the quarries in the most recent round of Local Authority Air Quality Review and assessment and concluded that it was unlikely that the air quality objectives would be exceeded at relevant receptor locations in the vicinity of the quarries.




<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.24: Modelled annual mean background PM10 concentrations in Edinburgh, 2006.

The predicted number of exceedences of the 24 hour limit value for PM10 of 50 μg m-3 was calculated from the annual mean value using the statistical relationship presented in Technical Guidance LAQM.TG(03) for Local Authority Review and Assessment. The predicted number of exceedences in Edinburgh is shown in Figure 3.25. The predicted number of exceedences at background locations is fewer than the objective for 2010 of 7 exceedences except in the vicinity of quarries in the west of Edinburgh.

No. of exceedences<2

2-5

5-7

7-10

10-20

>20

Figure 3.25: Modelled number of exceedences of the daily PM10 objective in Edinburgh, 2006



Figure 3.26 shows the predicted annual average PM2.5 concentrations for Edinburgh. The predicted concentration is less than the objective for 2020 of 12 μg m-3 at background locations throughout the city, except close to quarry operations in the west of the Council area.


8-10

10-12

12-14

14-16

>16

Figure 3.26: Modelled annual mean background PM2.5 concentrations in Edinburgh, 2006.



3.5.2 Business as usual, 2010: Edinburgh

Figure 3.27 shows the modelled annual mean PM10 concentration for the business as usual case for 2010. The modelled concentration in Edinburgh is less than the air quality objective for 2010 of 18 μg m-3 for much of the Council area. The modelled concentrations only exceeded the objective for 2010 close to the quarries in the rural west of Edinburgh.


<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.27: Modelled annual mean background PM10 concentrations in Edinburgh, business as usual, 2010.

The predicted number of exceedences of the 24 hour limit value for PM10 of 50 μg m-3 was calculated from the annual mean value using the statistical relationship presented in Technical Guidance LAQM.TG(03) for Local Authority Review and Assessment. The predicted number of exceedences in Edinburgh is shown in Figure 3.28. The number of exceedences is fewer than the objective for 2010 at background locations throughout Edinburgh.



No. of exceedences<2

2-5

5-7

7-10

10-20

>20

Figure 3.28: Number of exceedences of the daily PM10 objective in Edinburgh, business as

usual, 2010. Figure 3.29 shows the predicted annual average PM2.5 concentrations for Edinburgh. The predicted concentration is less than the objective of 12 μg m-3 for 2020 at background locations throughout the city. The predicted PM2.5 population-weighted mean concentration in Edinburgh was 8.7 μg m-3.


<8

8-10

10-12

12-14

14-16

>16

Figure 3.28: Modelled annual mean background PM2.5 concentrations in Edinburgh, business as usual, 2010



3.5.3 Future year 2010, with proposed biomass: Edinburgh

In order to assess the potential impact of biomass combustion on air quality in Edinburgh in 2010, it is necessary to know where the biomass combustion will occur and the quantities of heat to be provided. The City of Edinburgh Council has received planning applications for the installation of biomass combustion units for various developments. Permission has not yet been granted for many of these installations, but it may be granted at a later date for some sites. It is thus possible that biomass heating will be operating by 2010 at these sites. However, given the timescales involved, it is not likely that many other significant new installations will be in operation by 2010. The 2010 scenario assessed in this study assumes that all the biomass combustion sources identified from planning applications will be operational. It also includes four biomass combustion sources that have recently been installed in Edinburgh. These boilers are listed in Table 3.8.

Table 3.8: Potential biomass installations for 2010 in Edinburgh.

Site Boiler capacity (MW th)

Russell Road vehicle maintenance 0.36 Lochend Road Care Home 0.3 Botanical Gardens 0.15 Newbridge Industrial Estate 0.056 Bonaly Primary School 0.4 Holyrood 1.25 Juniper Green 0.04 Craigroyston 1.25 Forresters 1.25 St Augustines 1.25 Broughton 1.25

Table 3.9 shows the modelled point source discharge characteristics for each of the modelled developments. The average heat demand for each boiler unit was estimated assuming 30% utilisation. The average rate of emission was estimated based on emission factors of 20 g/GJ and 60 g/GJ representing the range of current boiler performance. As with the Dundee scenarios discharge flowrates at capacity were then estimated assuming a theoretical air requirement of 0.3 kg air per MJ (Chemical Engineers Handbook), 6% excess air and discharge at 100oC. Stack diameters were then selected from the set 0.1 m, 0.2 m, 0.5 m and 1 m based on the natural draught flowrates used in the development of the nomographs (Appendix 3). Stack heights above ground were then estimated using the nomographs with the aim of limiting the maximum local contribution to annual mean particulate matter concentrations from each individual plant operating at capacity to less than 1 μg m-3. It was assumed that each stack would discharge above a rectangular building 10 m high and 30 m square.



Table 3.9: Modelled point source discharge characteristics.

Location Particulate emission rate, g/s Stack height, m

Site Easting Northing

Boiler capacity (MW th)

Average heat load

(MW) 20 g/GJ 60 g/GJ

Diameter (m)

Discharge velocity

m s-1 20 g/GJ 60 g/GJ

Russell Road vehicle maintenance 323527 672829 0.36 0.108 0.00216 0.00648 0.5 1.32 12* 17

Lochend Road Care Home 327442 675405 0.3 0.09 0.0018 0.0054 0.5 1.10 12* 15

Botanical Gardens 324500 675500 0.15 0.045 0.0009 0.0027 0.5 0.55 11 13

Newbridge Industrial Estate 311900 672300 0.056 0.0168 0.000336 0.0010 0.2 1.28 11 12

Bonaly Primary School 321482 668135 0.4 0.12 0.0024 0.0072 0.5 1.47 13 17

Holyroode 328700 672600 1.25 0.375 0.0075 0.0225 1 1.15 15 19

Juniper Green 319737 669032 0.04 0.012 0.00024 0.00072 0.2 0.92 11 11

Craigroyston 321910 675795 1.25 0.375 0.0075 0.0225 1 1.15 15 19

Forresters 319623 671640 1.25 0.375 0.0075 0.0225 1 1.15 15 19

St Augustines 319570 671835 1.25 0.375 0.0075 0.0225 1 1.15 15 19

Broughton 323800 674900 1.25 0.375 0.0075 0.0225 1 1.15 15 19 *Estimated stake heights used during the model. Subsequent data showed that Russell Rd site has a stack height of approximately 3m and Lochend Rd approximately 8m.

Figure 3.30 shows the predicted contribution from the identified biomass installations to annual mean particulate matter concentrations for boilers with an emission factor of 60 g/GJ. The predicted contribution is less than 0.1 μg m-3 at most locations except close to the proposed boilers. The maximum predicted ground level concentration was 0.5 μg m-3 close to the installations at the Forresters and St Augustine’s schools. The maximum predicted contribution for boilers with a 20 g/GJ emission factor was 0.2 μg m-3. The contribution from the proposed developments has been added to the background concentrations for 2010. The resulting concentration maps cannot be distinguished from the business as usual case and hence, are not presented in this report.

Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.30: Modelled contribution to particulate matter concentrations from identified biomass installations in Edinburgh in 2010 assuming an emission factor of 60 g/GJ.



3.5.4 Business as usual 2020: Edinburgh

Figure 3.31 shows the modelled annual mean PM10 concentration for the business as usual case for 2020. The modelled concentration in Edinburgh is less than the air quality objective for 2010 of 18 μg m-3 for much of the Council area. The modelled concentrations only exceeded the objective for 2010 close to quarries in the rural west of Edinburgh.


<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.31: Modelled annual mean background PM10 concentrations in Edinburgh, 2020. The predicted number of exceedences of the 24 hour limit value for PM10 of 50 μg m-3 was calculated from the annual mean value using the statistical relationship presented in Technical Guidance LAQM.TG(03) for Local Authority Review and Assessment. The predicted number of exceedences in Edinburgh is less than the objective for 2010 at background locations throughout Edinburgh with the majority of the area experiencing less than 2 exceedences.

Figure 3.32 shows the predicted annual average PM2.5 concentrations for Edinburgh. The predicted concentration is less than the objective of 12 μg m-3 for 2010 at background locations throughout the city. The predicted PM2.5 population-weighted mean concentration in Edinburgh was 7.8 μg m-3, approximately 10% less than the mean predicted for 2010 (8.7μg m-3). This reduction may be set against the exposure reduction target of 15%. It is thus likely that the exposure reduction target will be difficult to meet even in the absence of biomass combustion.




<8

8-10

10-12

12-14

14-16

>16

Figure 3.32: Modelled annual mean background PM2.5 concentrations in Edinburgh, 2020.

3.5.5 Future year 2020, with substantial biomass combustion: Edinburgh

The scenario for 2020 with substantial biomass combustion has been derived by identifying potential sources from a number of groups of developments. These groups are as follows:

• Future housing developments already identified • Replacement of demolished housing • Modification at existing housing • Schools • Business development • Proposals for shops and other similar developments • Other institutions

The methodology used to estimate emissions from each of these sources is the same as was used for Dundee but due to the number of developments it is more detailed. The methodology is therefore described in detail in Appendix 2 whilst the impact of each sector is summarised in this section along with the modelled output of the cumulative effect of all of the developments.

Future housing developments

Two scenarios have been developed under this grouping. One assuming all new developments will be heated by centralised district heating (where heating is supplied from a small number of centralised biomass boilers or CHP systems), and one where all are heated by their own individual household boilers (individual heating systems). Figure 3.33 (and Figure A2.1 in Appendix 2) shows the modelled contribution to particulate matter concentrations from the identified housing developments for emission factors of both 20 g/GJ and 60 g/GJ and also both centralised district heating and individual heating systems. For centralised district heating with an emissions factor of 20 g/GJ the predicted impact is restricted to small areas close to the biomass installations. The maximum contribution to ground level annual mean concentrations is generally predicted to be less than 0.5 μg m-3 from these sources. For centralised district heating with an emissions factor of 60 g/GJ the predicted area of impact is substantially greater. Nevertheless, the maximum contribution to ground level annual mean concentrations is generally predicted to be less than 1 μg m-3 from these sources, except to the north east of a development in Leith where maximum contributions are modelled to be 2 μg m-3.



For individual heating systems with an emissions factor of 20 g/GJ the predicted impact is restricted to small areas close to the biomass installations. However, the impact is greater where there are large numbers of new houses in Leith and Granton. The maximum contribution from these sources to ground level annual mean concentrations is almost 2 μg m-3. For individual heating systems with an emissions factor of 60 g/GJ the maximum contribution from these sources to ground level annual mean concentrations is predicted to be almost 5 μg m-3. Emission factor of 20 g/GJ and centralised heating

Emission factor of 60 g/GJ and centralised heating

Emission factor of 20 g/GJ and individual heating systems


Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5 Figure 3.33: Modelled contribution to particulate matter concentrations from new housing

developments in 2020 in Edinburgh.




The contribution to annual mean concentrations from the replacement of demolished housing is predicted to be less than 0.1 μg m-3 for appliances with emission factors of 20 g/GJ. Figure A2.2 in Appendix 2 shows the predicted contribution from replacement houses fitted with biomass boilers with emission factors of 60 g/GJ. The predicted contribution remains less than 0.2 μg m-3 throughout Edinburgh, with the highest concentrations in the city centre.

Modification to existing housing

The contribution to annual mean concentrations from the installation of biomass heating in existing housing is predicted to be less than 0.1 μg m-3 for appliances with emission factors of 20 g/GJ. Figure A2.3 in Appendix 2 shows the predicted contribution from existing houses fitted with biomass boilers with emission factors of 60 g/GJ. The predicted contribution remains less than 0.2 μg m-3 throughout Edinburgh, with the highest concentrations in the suburbs surrounding the city centre.

Schools

Figure A2.4 in Appendix 2 shows the modelled contribution to particulate matter concentrations from biomass installations in all schools in Edinburgh assuming an emission factor of 60 g/GJ. The predicted contribution is less than 0.1 μg m-3 over most of the city, with higher concentrations in the vicinity of the schools. The maximum predicted contribution was less than 0.5 μg m-3. If the boilers operated with an emission factor of 20 g/GJ, the maximum predicted contribution was less than 0.2 μg m-3.

Business Developments

Figure A2.5 in Appendix 2 shows the modelled contribution from new business developments in Edinburgh if they were heated by biomass installations with an emission factor of 20 g/GJ and 60 g/GJ. For an emissions factor of 20 g/GJ the predicted contribution is less than 0.1 μg m-3 over most of Edinburgh, with higher contributions in the vicinity of the larger developments. The maximum contribution to annual mean concentrations was predicted to be 0.6 μg m-3. For installations with an emission factor of 60 g/GJ the predicted contribution is more than 0.1 μg m-3 over a substantial part of Rural West Edinburgh, with higher contributions in the vicinity of the larger developments. The maximum contribution to annual mean concentrations was predicted to be 1.1 μg m-3.

Proposals for shops and other similar developments

The modelled contribution from emissions from new redevelopments fitted with biomass heating is generally less than 0.1 μg m-3 throughout Edinburgh except in the immediate vicinity of the retail developments.

Other institutions

Figure A2.6 in Appendix 2 shows the modelled contribution from biomass installed in identified institutions in Edinburgh if they were heated by biomass installations with an emission factor of 60 g/GJ. The predicted contribution is more than 0.1 μg m-3 over a substantial part of the city, with higher contributions in the vicinity of the larger developments.

Total contributions from biomass combustion to particulate concentrations

Figure 3.34 shows the total contribution from biomass installed in new housing developments, rebuilt or renovated houses, a proportion of existing houses, all schools, new business developments, new retail developments and various institutions assuming that the emission factor is 20 g/GJ. It has been assumed that new housing developments are supplied with heat by centralised district heating from a small number of boilers or CHP plant. As discussed in section 3.3, chimney heights have been assigned to each development to limit the individual ground level contributions to annual mean concentrations to less than 1 μg m-3 for plant operating continuously at capacity. Figure 3.34 shows that it is predicted that annual mean particulate concentrations will increase by 0.2-0.5 μgm-3 in large parts of the city. Figure 3.35 shows the total contribution to annual mean particulate concentrations if the boilers operated with an emission factor of 60 g/GJ. It is predicted that annual mean particulate concentrations will increase by 0.5-1.0 μg m-3 in large areas of the city.



Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.34: Total modelled contribution to background particulate matter concentrations from biomass installations identified in Edinburgh in 2020 assuming an emission factor of 20 g/GJ.

Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure 3.35: Total modelled contribution to background particulate matter concentrations from biomass installations identified in Edinburgh in 2020 assuming an emission factor of 60 g/GJ.

3.5.6 Total concentrations

Figure 3.36 shows the sum of the modelled contributions from biomass combustion and the background PM10 concentration for biomass combustion with a 20 g/GJ emission factor. The predicted concentration is less than the objective for 2010 of 18 μg m-3 at all locations except near to the quarries and at one 1 km square in the city: the exceedence is small (0.01 μg m-3) at this location and the contribution from biomass combustion is also small (0.17 μg m-3) compared to the uncertainty in the background concentration.



Figure 3.37 similarly shows the sum of the modelled contributions from biomass combustion and the background PM10 concentration for biomass combustion with a 60 g/GJ emission factor. The predicted concentration is less than the objective for 2010 of 18 μg m-3 at all locations except near to the quarries and at one 1 km square in the city: the exceedence is small (0.13 μg m-3). There are fewer than two predicted exceedences of the 24-hour limit value of 50 μg m-3 in the city centre compared to the objective of less than 7 exceedences. Both of these scenarios demonstrate that, with the biomass boilers installed in all of the potential new developments, there is a contribution to PM10 background concentrations sufficient to move from no exceedences in the city centre to one of the 1km by 1km squares indicating an exceedence. It must be noted that this exceedences is very small (0.01μg m-3 with a 20 g/GJ emission factor and 0.13 μg m-3

with a 60 g/GJ emission factor) and as such this contribution needs to be put in perspective against other sources of emissions in the city centre, such as road traffic.


<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.36: Modelled annual mean PM10 concentrations in Edinburgh, 2020 with biomass installations emitting 20 g/GJ.




<14

14-16

16-18

18-20

20-22

22-24

24-26

26-28

Figure 3.37: Modelled annual mean PM10 concentrations in Edinburgh, 2020 with biomass installations emitting 60 g/GJ.

Figure 3.38 and Figure 3.39 show the predicted annual average PM2.5 concentrations in 2020 for Edinburgh including biomass combustion with emission factors of 20 g/GJ and 60 g/GJ. The predicted concentration is less than the objective of 12 μg m-3 for 2010 at background locations throughout the city in both cases. The predicted population-weighted concentration was 8.0 μg m-3 for biomass with emission factor of 20 g/GJ and 8.3 μg m-3 for biomass with emission factor of 60 g/GJ. This may be compared with 7.8 μg m-3 in 2020 without biomass and 8.7 μg m-3 in 2010. Hence, compared to the target 15% exposure reduction for PM2.5, there is a 10% reduction with no biomass, 8% reduction with biomass with 20g/GJ emission rate and a 5% reduction with biomass with a 60 g/GJ emission rate.


<8

8-10

10-12

12-14

14-16

>16

Figure 3.38: Modelled annual mean background PM2.5 concentrations in Edinburgh, 2020 with biomass installations emitting 20 g/GJ.




<8

8-10

10-12

12-14

14-16

>16

Figure 3.39: Modelled annual mean background PM2.5 concentrations in Edinburgh, 2020 with biomass installations emitting 60 g/GJ.

3.5.7 Summary for Edinburgh

Modelled annual mean PM10 concentrations in Edinburgh for 2006 were generally less than the objective for 2010 of 18 μg m-3, except in parts of the city centre, Newbridge and Queensferry and close to quarries in the rural west of Edinburgh. By 2010, the model predicts that the annual mean concentration will be less than the objective throughout the city in the absence of substantial biomass combustion, except near the quarries. Further small reductions in PM10 concentrations are predicted by 2020. The City of Edinburgh Council has received planning applications for the installation of biomass combustion units for various developments. The potential impact of these biomass installations for 2010 is small provided that the localised impacts are controlled to limit the maximum contribution to ground concentrations to less than 1 μg m-3 for operation at capacity18. Predicted contributions to particulate concentrations are generally less than 0.1 μg m-3 except in the immediate vicinity of the proposed installations. The operation of the proposed boilers will not lead to exceedences of the air quality objectives in 2010 at background locations in the city. The size and location of biomass combustion sources is not known for 2020. In this study, potential biomass installations have been identified in order to provide an assessment of the distribution of biomass combustion sources throughout the city. The current heat demand for Edinburgh of 24701 TJ per annum will increase as the result of the identified new developments, demolition and renovation to 26654 TJ. If biomass combustion was installed in each of the identified new developments, in some of the existing housing and in schools and other institutions identified, it is expected that it would provide a total of 3976 TJ of heat. This is 14.9% of the projected total heat demand. In practice, it will not be possible to install biomass heating in all the sites identified. In addition, there will be other sites, not yet identified, where biomass heating can be readily installed. Nevertheless, the analysis provides the basis for assessing the distribution of biomass combustion sources throughout the city and the effect on air quality of widespread adoption of biomass combustion. To a first

18 In this study, it has been assumed that this will be achieved by use of an appropriate chimney height. However, other measures, such as, additional emission abatement control systems, fuel type and boiler selection could be used to achieve the same outcome.



approximation the impact of biomass combustion will scale in proportion to the fraction of the heat demand met by biomass. To estimate the impact of biomass combustion at different uptake rates of biomass heating, the modelling outputs presented here will approximately scale in proportion to the fraction of the heat demand met by biomass. The combined effect of the potential biomass installations for 2020 depends on the emission rate and the design of the discharge stacks. Model runs were carried out assuming emission factors of 20 and 60 g/GJ representing the range of emissions measured in plant recently installed in Scotland. Chimney heights have been assigned to limit the individual ground level contributions from each development to annual mean concentrations to less than 1 μg m-3 for plant operating continuously at capacity. For the 20g/GJ emission factor, the effect of biomass combustion is to increase annual mean particulate matter concentrations across much of the city centre by 0.2-0.5 μg m-3. This equates to 1 to 4% of the modelled PM10 concentrations arising from all other sources in these city centre areas. For biomass combustion installations operating with emission factors of 60 g/GJ, the particulate concentrations are predicted to increase by 0.5-1.0 μg m-3 across large parts of the city. This equates to 4 to 7% of the modelled PM10 concentrations arising from all other sources in these city centre areas. The assessment has been based on the assumption that each development is provided by centralised district heating from a small number of biomass combustion plants. The alternative is to provide the heat from many individual biomass combustion plants throughout each development, for example, with a separate boiler for each dwelling. This would considerably increase the air quality impact of biomass combustion in some large developments - for example, the contribution to particulate concentrations in parts of new residential developments in Leith is predicted to be up to 5 μg m-3 for the case where heat is provided by many boilers distributed throughout the development. The model indicates that the air quality objective of 18 μg m-3 as an annual mean for PM10 will be exceeded in one additional 1 km square area in the city centre for the 2020 with biomass scenario. However, the modelled contribution from biomass combustion at this location is small compared with the uncertainty in the background concentration. It must be noted that these figures do not take into account any other sources of PM10 and these would need to be considered to determine the actual compliance with the air quality objectives across Edinburgh. The model predictions for 2006, 2010 and 2020 indicate that the daily mean objective for PM10 of less than 7 exceedences per year of the limit value of 50 μg m-3 will be met for all modelled scenarios, with and without biomass combustion, except in the vicinity of quarries in the west of the city. The predicted annual average PM2.5 concentrations for 2010 and 2020 are less than the objective for 2010 of 12 μg m-3 at background locations throughout Edinburgh for all scenarios, with and without biomass combustion. Compared to the exposure reduction target of 15% exposure PM2.5, there is a 10% reduction with no biomass, 8% reduction with biomass with 20g/GJ emission rate and a 5% reduction with biomass with a 60 g/GJ emission rate. Hence, the modelling scenarios without biomass installations indicate that it will already be difficult to achieve the 15% exposure reduction objective between 2010 and 2020. Based on the assumption in this study, the combined impact of widespread uptake of biomass installations could increase the difficulty in achieving this target, taking into account emissions from the main existing sources. Controlling emissions from biomass boilers to the lower range used in this study will minimise this impact and additional controls could be explored.



4 Air Quality Screening Tool for Biomass Combustion in Scotland

Local Authorities are required to review and assess air quality in their areas against objectives set out in the Government’s Air Quality Strategy. Technical Guidance LAQM.TG(03) provided advice on how to assess air quality. The Air Quality Strategy was revised in July 2007 and new Technical Guidance to support Local Authorities in their duties has been prepared and is currently the subject of consultation (Defra, 2008). The Technical Guidance is supported by a technical report describing the development of the Guidance for biomass combustion. This provides Local Authorities with a simple tool for assessing whether a biomass combustion installation in the range 50 kW to 20 MW thermal will lead to pollutant concentrations exceeding the air quality objectives or will compromise the effectiveness of measures set out in their Action Plans. This Technical Guidance was prepared for application across the United Kingdom as a whole. Further guidance and additional nomographs that are specific to Scotland have been developed within this study and detail is provided in Appendix 3. The additional guidance takes into account the more stringent air quality objectives that apply in Scotland and different meteorology. These new nomographs have also assisted with the modelling scenarios. The potential biomass installation information provided by the local authorities was not sufficiently detailed at this stage to provide details of stack heights. This information is an essential input into the modelling process. As described in Section 3.3, these stack heights were estimated using the nomographs in Appendix 3 with the aim of limiting the maximum local contribution to annual mean particulate matter concentrations from each individual plant operating at capacity to less than 1 μg m-3. Although in this study, it has been assumed that this will be achieved by use of an appropriate chimney height, other measures, such as, additional emission abatement control systems, fuel type and boiler selection could be used to achieve the same outcome.



5 Conclusions The key conclusions that have been drawn from this modelling study are discussed below.

1. The contribution of biomass to urban background ambient PM10 and PM2.5 concentrations is predicted to be less than about 1μgm-3 as an annual mean, compared to the Air Quality Objectives of 18μgm-3 and 12μgm-3 for PM10 and PM2.5 respectively.

These results can be taken as representative of the typical impact of biomass on background air quality in other Scottish towns and cities. Note however that this result is based on the following key assumptions:

• PM10 and PM2.5 emissions from biomass combustion units are at levels consistent with those currently achievable (i.e. between the best performing technology and emissions permitted for exempt appliances under the UK Clean Air Act);

• The heat supplied by biomass combustion is up to 15% of the city heat requirement; • Where appropriate, large high-density housing, commercial or industrial developments are

heated by means of centralised district heating systems with a small number of biomass combustion plants. The study provides an example which shows that at a large proposed housing development in Edinburgh, the use of a small number of centralised biomass boilers may contribute 0.5–1 μgm-3 to PM10 and PM2.5 concentrations, compared to a contribution of 2–5 μg m-3 for individual heating systems. A screening tool has been developed to allow Local Authorities to identify where there is a risk that many small boilers will combine to adversely affect air quality.

2. This additional contribution from biomass may be significant in some circumstances. The modelled results are based on the contribution to background concentrations. It would therefore be important to consider future biomass developments in context to local conditions and sources. The small contribution modelled here, for example, may be significant in locations where PM10 air quality concentrations are close to exceeding air quality objectives and in or near Air Quality Management Areas that have been declared for PM1o due to other sources (for example road traffic). They will be less significance in other areas.

3. Both scenarios used in this study demonstrate compliance with PM2.5 annual mean objectives, but a large uptake in biomass use, under the assumptions used in this study, could increase the difficulty in achieving the PM2.5 urban background exposure reduction target.

The modelled baseline (business as usual) scenarios without biomass installations indicate that it will be difficult to achieve the 15% exposure reduction objective between 2010 and 2020. With additional biomass combustion, the population-weighted mean exposure to PM2.5 in 2020 for the 20g/GJ case is predicted to increase by about 2% (for emissions at a 20g/GJ level) and 5–6 % (for emissions at the 60 g/GJ level). This equates to a change in the modelled 2% exposure reduction in Dundee to no reduction (for the 20g/Gj scenario) or a modelled 4% increase (for the 60g/GJ scenario), and a change in the modelled 10% reduction with no biomass to a smaller reduction of 8% (for the 20g/Gj scenario) or of 5% (for the 60g/GJ scenario) in Edinburgh. Based on the assumptions in this study, the combined impact of widespread uptake of biomass installations could increase the difficulty in achieving this objective. If there is a large uptake, additional controls on individual installations should be explored and additional reductions in the major sources of emissions sources will be required to achieve the exposure reduction target.



4. The emission limits in the Clean Air Act are not adequate to ensure that emission levels from biomass units (or other relevant fuels) are within 20 or 60g/GJ.

The Clean Air Act provides a mechanism for Local Authorities to control installation of furnaces in developments. However, this Act was developed primarily to control emissions from coal combustion and is not entirely appropriate to biomass combustion in modern appliances. The Act requires all new non-domestic furnaces to be notified to Local Authorities and solid fuel appliances >45.4kg/h need to be approved by Local Authorities. This provides a mechanism for Local Authorities to control potential impacts on air quality by emissions from larger biomass combustion appliances by adopting guidelines on PM emission. However emissions from domestic furnaces and solid fuel furnaces <45.4 kg/h (potentially as large as 200 kW output) would not be subject to such approval. Within smoke control areas domestic and non-domestic solid fuel appliances need to be approved (that is it has been tested to demonstrate capability of operating with no substantial smoke). However, the emission limits applied to appliances exempted for use in smoke control areas are NOT sufficient to guarantee operation at 60g/GJ. The emission rates for particulate matter used in this assessment are therefore considerably smaller than the limits required under the Clean Air Act. It follows that biomass combustion installations operating at the Clean Air Act limits would have a substantially greater impact than those modelled here. Further changes to the Clean Air Act to limit the emissions from solid fuel combustion have been proposed by BERR in its recent consultation document on the UK Renewable Energy Strategy. In the light of the findings of this study there is a need to review the provisions of the Clean Air Act and to consider the way the planning system operates in practice, so as to take better account of the potential cumulative air quality impacts of district level biomass boilers in urban areas to help ensure that fine particulate levels do not exceed national and EU limit values. In addition, potential costs and benefits of emission abatement equipment, such as particulate filters, to reduce PM10 and PM2.5 emissions could usefully be explored for certain boilers, especially in urban areas where levels are close to EU or national objectives for air quality. However, investigation of specific changes to the Clean Air Act, planning guidance and cost benefit analysis are beyond the scope of this report.

5. The importance of appropriate boiler specification

The emission performance of any biomass boiler system is dependent on the specification of the combustion equipment and its suitability to match the load applied at the site. Research in other European Countries where biomass combustion has been well established indicates that the design of system as a whole (including fuel type, abatement equipment and stack height etc.) is as important as the equipment specified.

For example, stack heights need to be specified to limit the individual ground level contributions from each boiler to annual mean concentrations to less than 1μg m-3 in order to ensure that the overall impact of biomass combustion remains within the results predicted in this study. Lower stack heights will achieve this result when emissions from individual boilers are further controlled by boiler design, specification and rating, fuel type and quality and/or use of emission abatement equipment.



6 References Abbott J (2008). Technical Guidance: Screening assessment for biomass boilers. AEA/ED48673005/R2655- Issue 1. AEA Energy and Environment. July 2008.

Abbott J, Barker N, Coleman P, Howes P, Stewart R, Leonard A, Collings A (2007). Review of the Potential Impact on Air Quality from Increased Wood Fuelled Biomass Use in London. AEA/ENV/R/2495/Issue 2 December 2007.

Abbott J, Stedman J and Vincent K (2007a). Auditing the contribution of Environment Agency regulated processes to pollution – Part 1. Science Report SC030172/SR2. Environment Agency. ISBN: 978-1-84432-686-0.

Abbott J, Stedman J and Vincent K (2007b). Auditing the contribution of Environment Agency regulated processes to pollution – Part 2. Science Report SC030172/SR3. Environment Agency. ISBN: 978-1-84432-685-3.

Angus Council and Dundee City Council (2007). Audit of housing land in Dundee and Angus. http://www.angus.gov.uk/housinglandaudit2007/housingaudit2007.pdf

AQEG (2005). Particulate matter in the United Kingdom. Air Quality Expert Group. Defra, London. ISBN 0-85521-143-1.

BERR (2008). Total final energy consumption at regional and local authority level – 2005. Publication URN 08/P1c. Excel spreadsheet found at http://www.berr.gov.uk/files/file42995.xls

City of Edinburgh Council (2006). Updating and Screening Assessment Report - Review and Assessment of Air Quality. Round 3 - Local Air Quality Management 2006. http://www.edinburgh.gov.uk/internet/Attachments/Internet/Environment/Environmental_health/Pollution/Air_pollution/Air_quality/Air%20Quality%20Round%203.pdf

COMEAP (1998). The quantification of the effects of air pollution on health in the United Kingdom. HMSO. London.

Defra (2008). Local air quality management – technical guidance TG(08). Consultation document. Department for Environment, Food and Rural Affairs in partnership with the Scottish Executive, Welsh Assembly Government and Department of the Environment Northern Ireland. June 2008. http://www.defra.gov.uk/corporate/consult/airqualitymanage-guidance/technical-guidance.pdf

Defra (2007). The Air Quality Strategy for England, Scotland, Wales and Northern Ireland (Volume 1). Department for Environment, Food and Rural Affairs in partnership with the Scottish Executive, Welsh Assembly Government and Department of the Environment Northern Ireland. July 2007. http://www.defra.gov.uk/environment/airquality/strategy/pdf/air-qualitystrategy-vol1.pdf

Dundee City Council (2003). Local authority updating and screening assessment. May 2003. http://www.dundeecity.gov.uk/dundeecity/uploaded_publications/publication_174.pdf

Dundee City Council (2002). Dundee and Angus structure plan 2001-2016. http://www.dundeecity.gov.uk/structureplan/index.php

Nussbaumer T, Czasch C, Klippel N, Johansson L, Tullin C (2008). Particulate emissions from biomass, combustion in IEA countries - Survey on measurements and emission factors. International Energy Agency (IEA) Bioenergy Task 32, Swiss Federal Office of Energy (SFOE). Zurich January 2008. http://www.ieabcc.nl/publications/Nussbaumer_et_al_IEA_Report_PM10_Jan_2008.pdf

Perry RH and Green DW (eds) (2007). Perry’s chemical engineers handbook. 8th edition. McGraw-Hill, October 2007.

Scottish Executive (2008). Scotland’s Renewable Heat Strategy: Recommendations to Scottish Ministers. Renewable Heat Group (RHG) Report 2008. The Scottish Government, February 2008.

Scottish Executive (2007). Biomass action plan for Scotland. Scottish Executive, March 2007.

Statutory Instrument No. 2325 (1007). The Large Combustion Plants (National Emission Reduction Plan) Regulations 2007. http://www.opsi.gov.uk/si/si2007/uksi_20072325_en_1.



Appendices

Appendix 1: Emissions Test Results

Site A Emissions results

O2 H2O Flow PM10 PM2.5 Cutpoint Velocity Gas Temp Moisture Oxygen Emission

factor Test %, dry % m3s-1 mgm-3 mgm-3 µm m/s oC % % g/GJ

1 9.9 5.7 0.09 45.9 - 10.8 3.0 186 5.7 9.9 26.6

2 9.9 6.0 0.08 53.2 - 10.9 3.0 206 6.0 9.9 30.9

3 10.2 5.8 0.08 48.1 - 11.0 3.0 213 5.8 10.2 27.9

4 9.8 7.6 0.09 - 38.8 2.7 3.0 159 7.6 9.8 22.5

5 10.4 7.6 0.09 - 9.7 2.3 3.0 176 7.6 10.4 5.6

6 9.9 5.2 0.09 - 34.2 2.7 3.0 205 5.2 9.9 19.9 Flow rates are expressed for a dry gas at STP, 101.3kPa, 273K, referenced to 11% Oxygen w/v concentrations are expressed for a dry gas at STP, 101.3kPa, 273K, referenced to 11% Oxygen

Fuel analysis

Sample Reference AET035 – Site A

Total Moisture % 15.0

Ash % 0.3

Sulphur % 0.01

Gross Calorific Value kJ/kg 17344

Net Calorific Value kJ/kg * 15915

Carbon % 42.9

Hydrogen % ** 5.0

Nitrogen % 0.19 *Calculated using determined values. ** Hydrogen corrected for moisture.



Site B Emissions results



1 16.0 3.8 0.3 96.1 - 9.8 12.0 164 3.8 16.0 55.8

2 16.3 3.7 0.3 93.5 - 9.7 12.0 162 3.7 16.3 54.3

3 20.3 2.2 0.1 - - 9.5 12.0 135 2.2 20.3

4 16.7 4.5 0.3 - 80.9 2.7 12.0 170 4.5 16.7 47.1

5 16.6 4.2 0.3 - 67.2 2.6 12.0 162 4.2 16.6 39.1


Fuel analysis

Sample Reference AET035 – Site B


Ash % 0.3

Sulphur % 0.01



Carbon % 42.5

Hydrogen % ** 4.9

Nitrogen % 0.22 *Calculated using determined values ** Hydrogen corrected for moisture.



Site C Emissions results



1 12.0 7.4 0.1 33.3 - 9.5 2.9 136 7.4 12.0 19.3

2 12.1 6.1 0.1 18.7 - 9.2 2.8 139 6.1 12.1 10.9

3 13.6 4.5 0.1 25.2 - 10.9 2.8 144 4.5 13.6 14.6

4 14.3 4.6 0.1 - 37.9 2.2 2.9 144 4.6 14.3 22.0

5 11.9 5.2 0.1 - 24.9 2.3 2.8 145 5.2 11.9 14.4


Fuel analysis

Sample Reference AET035 – Site C


Ash % 0.3

Sulphur % 0.01



Carbon % 42.7

Hydrogen % ** 4.9




Site D Emissions results



1 11.7 7.3 0.05 77.9 - 9.3 1.4 79 7.3 11.7 45.2

2 12.5 9.7 0.04 - 48.6 2.3 1.4 84 9.7 12.5 28.2

3 12.0 4.9 0.05 86.6 - 9.5 1.4 81 4.9 12.0 50.3

4 14.1 7.1 0.03 - 58.8 2.3 1.4 85 7.1 14.1 34.1

5 15.4 4.6 0.03 159.9 - 9.8 1.5 92 4.6 15.4 92.8

6 13.2 8.9 0.04 - 79.2 2.4 1.5 91 8.9 13.2 46.0

7 12.8 5.9 0.04 103.1 - 9.5 1.5 86 5.9 12.8 59.8

8 14.4 6.7 0.04 - 119.9 2.4 1.5 84 6.7 14.4 69.6

9 13.3 4.1 0.04 114.9 - 9.1 1.5 82 4.1 13.3 66.7

10 13.6 6.7 0.04 77.8 - 9.4 1.5 94 6.7 13.6 45.2

11 15.6 4.0 0.03 - 150.2 2.5 1.5 92 4.0 15.6 87.2

12 13.0 5.6 0.04 107.3 - 9.6 1.5 85 5.6 13.0 62.3

13 13.8 4.5 0.04 - 82.6 2.4 1.5 84 4.5 13.8 47.9


Fuel analysis

Sample Reference AET035 – Site D


Ash % 0.3

Sulphur % 0.01



Carbon % 46.2

Hydrogen % ** 5.3




Site E Emissions results



1 19.0 1.9 0.01 5.3 - 9.2 1.7 40 1.9 19.0 3.1

2 16.0 5.8 0.02 - 4.2 2.3 1.7 61 5.8 16.0 2.4

3 7.0 4.8 0.04 43.4 - 10.4 1.7 210 4.8 7.0 25.2

4 7.1 13.2 0.04 - 29.6 2.8 1.7 207 13.2 7.1 17.2

5 9.0 5.3 0.04 48.8 - 8.9 1.5 129 5.3 9.0 28.3

6 10.9 8.2 0.03 - 41.6 2.3 1.5 161 8.2 10.9 24.1

7 11.0 3.4 0.03 55.9 - 9.3 1.5 140 3.4 11.0 32.5

8 10.3 3.7 0.03 - 55.7 2.2 1.5 112 3.7 10.3 32.4

9 7.5 12.7 0.03 32.0 - 9.8 1.6 215 12.7 7.5 18.6

10 8.8 9.5 0.03 - 33.0 2.4 1.6 196 9.5 8.8 19.2

11 7.9 11.1 0.04 31.0 - 9.0 1.6 160 11.1 7.9 18.0

12 8.8 8.2 0.03 - 32.4 2.5 1.6 195 8.2 8.8 18.8

13 7.9 4.9 0.04 611.7 - 9.1 1.5 92 4.9 7.9 355.1


Fuel analysis

Sample Reference AET035 – Site E


Ash % 0.3

Sulphur % 0.01



Carbon % 46.2

Hydrogen % ** 5.3




Site F Emissions results



1 14.4 5.5 0.2 38.2 - 9.9 4.1 110 5.5 14.4 22.1

2 14.0 5.9 0.2 - 33.1 2.5 3.8 113 5.9 14 19.2

3 14.5 5.7 0.2 59.2 - 9.9 4.0 104 5.7 14.5 34.4

4 14.3 5.6 0.2 - 31.9 2.5 4.1 108 5.6 14.3 18.5

5 14.3 5.1 0.2 27.7 - 10.2 3.9 109 5.1 14.3 16.1

6 13.9 6.0 0.2 - 34.5 2.5 3.9 109 6 13.9 20.0

7 14.0 5.3 0.2 40.2 - 10.0 4.1 106 5.3 14 23.4

8 14.5 5.8 0.2 - 34.6 2.5 4.1 108 5.8 14.5 20.1

9 14.2 5.4 0.2 35.9 - 9.9 3.9 107 5.4 14.2 20.9

10 14.3 5.5 0.2 - 30.1 2.5 3.9 107 5.5 14.3 17.5

11 14.5 5.0 0.2 52.5 - 9.9 4.1 117 5 14.5 30.5

12 14.6 5.2 0.2 - 27.1 2.5 4.1 111 5.2 14.6 15.7

13 14.8 5.8 0.1 53.8 - 9.9 3.9 107 5.8 14.5 31.2


Fuel analysis

Sample Reference AET035 – Site F


Ash % 0.3

Sulphur % 0.01



Carbon % 43.91

Hydrogen % ** 4.88




Appendix 2: Edinburgh Scenario Development and Modelling Results for 2020 with Substantial Biomass Combustion The scenario for 2020 with substantial biomass combustion has been derived by identifying potential sources from a number of groups of developments. These groups are as follows:

• Future housing developments already identified • Replacement of demolished housing • Modification at existing housing • Schools • Business development • Proposals for shops and other similar developments • Other institutions

The methodology used to estimate emissions from each of these sources is described in detail below. For some development groups, the modeled contributions from biomass with an emission factor of 20g/GJ was less than 0.1 μgm-3 throughout the modeled area and hence, could not be shown on a concentration map.

Housing developments identified in the local plans

The Edinburgh City Local Plan has identified sites throughout the city centre in the areas listed in Table A2.1, whilst the Rural West Edinburgh Local Plan identifies further sites for housing development shown in Table A2.2.

Table A2.1: Housing developments listed in the Edinburgh City Local Plan.

Status Local Plan Reference Site location Estimated capacity

(no. households)

WAC 1a Leith Waterfront (Western Harbour) 2400

WAC 2 Granton Waterfront 6000

CA 4 Quartermile 1000

HSG 1 Craigs Road (SASA) 280

HSG 2 Chesser Avenue 275

HSG 3 Hyvots 310

HSG 4 Lochend Butterfly 356

HSG 5 New Greendykes 810

HSG 6 Greendykes 990

Existing housing sites

HSG 7 Nidrie Mains 600

WAC 1b Leith Waterfront (Leith Docks) 18000

WAC 1c Leith Waterfront (Salamander Place) Not yet determined

CA 3 Fountainbridge 1200

HSG 8 Clermiston Campus 295

Sites to meet strategic housing land requirements

HSG 9 Telford College (North Campus) 300




(no. households)

HSG 10 Telford College (South Campus) 350

HSG 11 Meadowbank 800

HSG 12 Eastern General Hospital 275

HSG 13 Newcraighall North 200

HSG 14 Newcraighall East 220

HSG 15 Edinburgh Zoo 100

HSG 16 Powderhall 100

HSG 17 South Gyle Wynd 180

HSG 18 Shrub Place 400

Other new housing sites

HSG 19 City Park 280

Table A2.2: Housing developments listed in the Rural West Edinburgh Local Plan.


(households)

HSG 1 Kinleith Mill To be established

HSG 2 Springfield 150

HSG 3 Baird Road 6

HSG 4 Hawthornbank 23

HSG 5 Stewart Terrace 117

HSG 6 Port Edgar To be established

Existing housing sites

HSG 7 Society Road To be established

HSP1 North Kirkliston 610*

HSP2 Main Street West, Kirkliston 90

HSP3 Kirkliston Distillery, Kirkliston 103

HSP4 Newbridge Nursery, Newbridge 25

HSP5 Hillwood Road, Ratho Station 50*

HSP6 Craigpark Quarry, Ratho 80

Sites to meet strategic housing land requirements

HSP7 Freelands Road Ratho 100

* Housing on these greenfield sites shall not be occupied before the West Edinburgh Tram to Newbridge is operational or its funding has been committed or, in the event of this not being delivered, other strategic (or strategically significant) improvements in public transport accessibility to the area have been secured. The Council has published The Edinburgh Standards for Sustainable Building19 as Supplementary Planning Guidance. Priority Standard 1 on energy efficiency states:

“The Council will require all new build developments with floor space of 1000 square metres or more, or ten residential units or more, or a site of 0.5 ha or more to reduce

19http://www.edinburgh.gov.uk/internet/environment/planning_buildings_i_i_/planning/planning_policies/CEC_edinburgh_standards_for_sustainable_buildings



predicted carbon dioxide emissions to a Buildings Emission Rating (BER) which attains a Target Emissions Rating (TER) minus 5%.”

Priority Standard 2 on on-site renewable energy generation states that:

“The Council will require in all developments, either new build or conversion, with floor space of 1000 square metres or more, or ten residential units or more, or a site of 0.5 ha or more, a minimum of 10% (20% in Areas of major Change developments of 2000 sq m or 20 residential units or more) of its remaining energy requirements to be supplied by on-site renewable energy generation. This on-site renewable energy generation must provide at least a further 10% (20% in AMCs) reduction in the development’s CO2 emissions. (This CO2 reduction is further to that achieved through the improved efficiency priority standard)”.

In 2007, the Scottish Buildings Standards Agency produced A Low Carbon Buildings Standard Strategy for Scotland-the Sullivan report20. The Sullivan report recommended for new buildings:

• Net zero carbon buildings (i.e. space and water heating, lighting and ventilation) by 2016/2017, if practical;

• Two intermediate stages on the way to net zero carbon buildings, one change in energy standards in 2010 (low carbon buildings) and another in 2013 (very low carbon buildings);

• The 2010 change in energy standards for non-domestic buildings should deliver carbon dioxide savings of 50% more than 2007 standards;

• The 2010 change in energy standards for domestic buildings should deliver carbon dioxide savings of 30% more than 2007 standards;

• The 2013 change in energy standards for non-domestic buildings should deliver carbon dioxide savings of 75% more than 2007 standards.

• The 2013 change in energy standards for domestic buildings should deliver carbon dioxide savings of 60% more than 2007 standards;

• Backstop levels of U-values and air-tightness for building fabric should be improved in 2010 to match those of Nordic countries, but consideration must be given to the social and financial impact of measures that would necessitate mechanical ventilation with heat recovery in domestic buildings;

• The ambition of total-life zero carbon buildings by 2030. The report also recommended that consideration be given to developing practical performance standards for existing buildings. The Target Emissions Rating for any development will depend on the size and design of the building and the heating and cooling system. The Scottish Buildings Standards Agency commissioned Turner and Townsend to undertake a report on The impact on costs and construction practice in Scotland of any further limitation of carbon dioxide emissions from new buildings21. Turner and Townsend carried out case studies for typical new detached houses (100 m2 floor area), mid-level flats (80 m2 floor area) and office buildings. They calculated Building Emissions Ratings and Target Emissions Ratings and assessed the potential for improvement resulting from a range of measures including improved insulation and airtightness and the use of biomass and other on-site renewable energy sources. The Turner and Townsend report calculated that the carbon dioxide emissions associated with space and water heating for detached houses and mid-level flats meeting the Target Emissions Rating were 2123 kg/year and 1287 kg/year respectively. Assuming a carbon dioxide emission factor of 51.35 kg/GJ gross (approximately 57.09 kg/GJ net22), this corresponds to heat demands of 41 and 25 GJ per annum for the detached house and the mid-level flat respectively.

20 http://www.sbsa.gov.uk/pdfs/Low_Carbon_Building_Standards_Strategy_For_Scotland.pdf 21 http://www.sbsa.gov.uk/pdfs/T&T_Final_Report2.pdf 22 http://www.ghgi.org.uk/unfccc.html



The Turner and Townsend study indicated that the Edinburgh Standards Priority 1 of up to 5% reduction in carbon dioxide emissions can be readily met by means of increased insulation (above the 2007 requirements), airtightness and low energy lighting. In addition, the further reduction of 20% of a development’s carbon dioxide emissions specified in Priority Standard 2 can be achieved readily using biomass. In combination, improved insulation, airtightness and biomass can go a long way towards meeting the recommendations in the Sullivan report. Potential financial and carbon savings from renewable energy technologies identified in the Edinburgh Standards are shown in Table A2.3 These suggest that biomass will be favoured on cost effectiveness grounds by many developers.

Table A2.3: Potential financial and carbon savings from renewable energy technologies.

System Cost (£/house)

Lifetime carbon dioxide saved (tonnes)

Kg carbon dioxide per £

CHP 4600 17808 3.9

Large wind 1125 30100 26.8

Small wind 7400 33080 4.5

PV 8000 19350 2.4

Solar thermal 2500 7600 3.0

Ground source heat pump 5000 6533 1.3

Biomass 3000 29260 9.8 The housing mix in the new developments is uncertain. The Council’s Policy House 2 is that the Council will seek the provision of a mix of house types and sizes where practical, to meet a range of housing needs, including those of families, older people and people with special needs. For this assessment, it has therefore been assumed that the average dwelling in the new developments will have a heat demand of 30 GJ per annum (taking account of Priority 1). Table A2.4 shows the estimated heat demand for each of the housing developments. The total annual heat demand from these sites is 1153 TJ corresponding to approximately 4.7% of Edinburgh’s current heat demand. It has been assumed here as the worst case that the whole of the heat demand for the new developments will be met by biomass combustion. Two cases have been considered:

1. The heat is supplied to each household through individual boilers (“distributed boilers”);

2. The heat is supplied to each household from a small number of centralised boilers (“district heating”).

Table A2.4 also shows the annual particulate emission for each development based on a particulate emission factor of 20 g/GJ and assuming that the biomass boilers have similar efficiency to the gas boilers used in the Turner and Townsend study (91.5%). The emissions are three times greater for an emission factor of 60 g/GJ. For developments with greater than 500 households and district heating, it has been assumed that the heat is supplied by biomass Combined Heat and Power (CHP) with 46% thermal efficiency. It has also been assumed that the electricity generated is exported to the grid, rather than used for electrical heating within the development. For the Leith Waterfront development (WAC 1b), the boiler capacity may exceed 50 MW thermal and so the plant may come under Integrated Pollution Prevention and Control regime. A lower emission factor of 10 g/GJ has been applied for this plant, corresponding approximately to emission benchmarks for plant of this capacity where best available technology is applied.



Table A2.5 shows the modelled discharge point source discharge characteristics for each of the modelled district heating developments. The thermal capacity of each unit was estimated assuming 30% utilisation for boiler units and 45% utilisation for CHP units. Discharge flowrates at capacity were then estimated assuming a theoretical air requirement of 0.3 kg air per MJ (Chemical Engineers Handbook), 6% excess air and discharge at 100oC. Stack diameters were then selected from the set 0.1 m, 0.2 m, 0.5 m and 1 m based on the natural draught flowrates used in the development of the nomographs (Appendix 3). It was assumed that large installations (excluding WAC 1b) would have multiple stacks with 1 m stack diameter. The WAC1b effective stack diameter was selected assuming a discharge velocity of 10 m s-1. Stack heights above ground were then estimated using the nomographs with the aim of limiting the maximum local contribution to annual mean particulate matter concentrations from each individual plant to less than 1 μg m-3. It was assumed that each stack would discharge above a rectangular building 10 m high and 30 m square.



Table A2.4: Heat demand and particulate emissions from new housing developments.

Local Plan Reference Site location

Estimated capacity (no. households)

Modelled capacity (no. households)

Heat demand

(TJ)

Heat only PM emission

(kg/annum)

PM emission (kg/annum with

some district heating)

WAC 1a Leith Waterfront (Western Harbour) 2400 2400 72 1440 2880

WAC 2 Granton Waterfront 6000 6000 180 3600 7200

CA 4 Quartermile 1000 1000 30 600 1200

HSG 1 Craigs Road (SASA) 280 280 8.4 168 168

HSG 2 Chesser Avenue 275 275 8.3 165 165

HSG 3 Hyvots 310 310 9.3 186 186

HSG 4 Lochend Butterfly 356 356 10.7 213.6 214

HSG 5 New Greendykes 810 810 24.3 486 972

HSG 6 Greendykes 990 990 29.7 594 1188

HSG 7 Nidrie Mains 600 600 18 360 720

WAC 1b Leith Waterfront (Leith Docks) 18000 18000 540 10800 10800

WAC 1c Leith Waterfront (Salamander Place)

Not yet determined 800 24 480 960

CA 3 Fountainbridge 1200 1200 36 720 1440

HSG 8 Clermiston Campus 295 295 8.9 177 177

HSG 9 Telford College (North Campus) 300 300 9 180 180

HSG 10 Telford College (South Campus) 350 350 10.5 210 210

HSG 11 Meadowbank 800 800 24 480 960

HSG 12 Eastern General Hospital 275 275 8.3 165 165

HSG 13 Newcraighall North 200 200 6 120 120

HSG 14 Newcraighall East 220 220 6.6 132 132

HSG 15 Edinburgh Zoo 100 100 3 60 60

HSG 16 Powderhall 100 100 3 60 60

HSG 17 South Gyle Wynd 180 180 5.4 108 108

HSG 18 Shrub Place 400 400 12 240 240

HSG 19 City Park 280 280 8.4 168 168

HSG 1 Kinleith Mill To be established 250 7.5 150 300

HSG 2 Springfield 150 150 4.5 90 90

HSG 3 Baird Road 6 6 0.18 3.6 3.6

HSG 4 Hawthornbank 23 23 0.69 13.8 14

HSG 5 Stewart Terrace 117 117 3.51 70.2 70

HSG 6 Port Edgar To be established 200 6 120 240

HSG 7 Society Road To be established 100 3 60 120

HSP1 North Kirkliston 610 610 18.3 366 732

HSP2 Main Street West, Kirkliston 90 90 2.7 54 54

HSP3 Kirkliston Distillery, Kirkliston 103 103 3.09 61.8 61

HSP4 Newbridge Nursery, Newbridge 25 25 0.75 15 15

HSP5 Hillwood Road, Ratho Station 50 50 1.5 30 30

HSP6 Craigpark Quarry, Ratho 80 80 2.4 48 48

HSP7 Freelands Road Ratho 100 100 3 60 60



Table A2.5: Modelled discharge characteristics for housing developments with district heating in Edinburgh.

Height (m) Local Plan Reference Site location Easting

(m) Northing

(m)

Average emission rate, g/s

for 20 g/GJ emission factor

Thermal capacity

(MW)

Diameter (m)

No. units

Discharge velocity (m s-1) 20 g/GJ 60 g/GJ

WAC 1a Leith Waterfront (Western Harbour) 25800 77400 0.0913 10.1 1 2 4.6 25 38

WAC 2 Granton Waterfront 23500 77500 0.2283 25.4 1 5 4.6 33 50

CA 4 Quartermile 25600 72900 0.0381 4.2 1 1 3.9 20 28

HSG 1 Craigs Road (SASA) 18200 73600 0.0053 0.9 1 1 0.8 16 18

HSG 2 Chesser Avenue 22200 71400 0.0052 0.9 1 1 0.8 16 18

HSG 3 Hyvots 28800 68600 0.0059 1.0 1 1 0.9 16 18

HSG 4 Lochend Butterfly 27400 74700 0.0068 1.1 1 1 1.0 16 19

HSG 5 New Greendykes 30100 70900 0.0308 3.4 1 1 3.1 21 25

HSG 6 Greendykes 29700 71200 0.0377 4.2 1 1 3.8 20 27

HSG 7 Nidrie Mains 29300 71800 0.0228 2.5 1 1 2.3 18 23

WAC 1b Leith Waterfront (Leith Docks) 27400 77300 0.3425* 76.1 2.6 1 10.0 40* 40*

WAC 1c Leith Waterfront (Salamander Place) 27800 76100 0.0304 3.4 1 1 3.1 19 25

CA 3 Fountainbridge 24500 72800 0.0457 5.1 1 1 4.6 20 29

HSG 8 Clermiston Campus 19900 73800 0.0056 0.9 1 1 0.9 16 18

HSG 9 Telford College (North) 23000 76100 0.0057 1.0 1 1 0.9 16 18

HSG 10 Telford College (South) 23100 75500 0.0067 1.1 1 1 1.0 16 19

HSG 11 Meadowbank 27800 74300 0.0304 3.4 1 1 3.1 19 25

HSG 12 Eastern General Hospital 28600 75500 0.0052 0.9 1 1 0.8 16 18

HSG 13 Newcraighall North 31900 72000 0.0038 0.6 0.5 1 2.3 14 20

HSG 14 Newcraighall East 32300 71800 0.0042 0.7 0.5 1 2.6 14 20

HSG 15 Edinburgh Zoo 20600 73200 0.0019 0.3 0.5 1 1.2 12 16

HSG 16 Powderhall 25800 75500 0.0019 0.3 0.5 1 1.2 12 16

HSG 17 South Gyle Wynd 19300 72000 0.0034 0.6 0.5 1 2.1 14 18

HSG 18 Shrub Place 26300 75100 0.0076 1.3 1 1 1.2 15 20

HSG 19 City Park 23500 76000 0.0053 0.9 1 1 0.8 16 18

RHSG 1 Kinleith Mill 18900 68000 0.0095 0.8 0.5 1 2.9 17 21

RHSG 2 Springfield 11500 78400 0.0029 0.5 0.5 1 1.7 14 18

RHSG 3 Baird Road 14000 70900 0.0001 0.0 0.2 1 0.4 11 11

RHSG 4 Hawthornbank 13000 78300 0.0004 0.1 0.2 1 1.7 11 12

RHSG 5 Stewart Terrace 12700 78100 0.0022 0.4 0.5 1 1.4 12 15

RHSG 6 Port Edgar 12300 78700 0.0076 0.6 0.5 1 2.3 17 22

RHSG 7 Society Road 11600 78700 0.0038 0.3 0.5 1 1.2 14 15

HSP1 North Kirkliston 12500 76100 0.0232 2.6 1 1 2.4 18 23

HSP2 Main Street West, Kirkliston 11800 75500 0.0017 0.3 0.5 1 1.0 12 15

HSP3 Kirkliston Distillery, Kirkliston 12300 75200 0.0020 0.3 0.5 1 1.2 12 15

HSP4 Newbridge Nursery, Newbridge 12100 72800 0.0005 0.1 0.2 1 1.8 11 13

HSP5 Hillwood Road, Ratho Stn 13500 72500 0.0010 0.2 0.5 1 0.6 11 14

HSP6 Craigpark Quarry, Ratho 13000 70600 0.0015 0.3 0.5 1 0.9 12 15

HSP7 Freelands Road Ratho 14200 71000 0.0019 0.3 0.5 1 1.2 12 16 * 10 g/GJ for plant >50 MW



The emissions for the distributed boiler case were allocated to the nearest 1 km square and were modelled as 1 km x 1 km volume sources, 10 m deep. The Leith Waterfront (Leith Docks) and Granton Waterfront developments extend over more than 1 km2 and so the emissions for these sources have been allocated over several km2 according to the area of the developments. Figure A2.1 shows the modelled contribution to particulate matter concentrations from the identified housing developments for emission factors of 20 g/GJ and 60 g/GJ for both distributed and district heating. Emission factor of 20 g/GJ and centralised heating

Emission factor of 60 g/GJ and centralised heating



Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5 Figure A2.1: Modelled contribution to particulate matter concentrations from new housing developments in 2020 in Edinburgh. The predictions for district heating are based on the assumption that heat will be supplied via district heating from a small number of biomass boilers or CHP systems. Generally, the



predicted impact is restricted to small areas close to the biomass installations. The maximum contribution to ground level annual mean concentrations is generally predicted to be less than 0.5 μg m-3 from these sources. For district heating assuming a larger emission factor of 60 g/GJ, the larger emissions have been taken into consideration when estimating stack heights so that the modelled stack heights are considerably greater than for the 20 g/GJ case. The predicted area of impact is substantially greater than for the 20 g/GJ emission factor case. Nevertheless, the maximum contribution to ground level annual mean concentrations is generally predicted to be less than 1 μg m-3 from these sources, except on the seaward side of the WAC 1b development in Leith. Generally, the predicted impact assuming a distributed boiler case with the 20 g/GJ emission factor is restricted to small areas close to the biomass installations. However, the impact is greater where there are large numbers of new houses in Leith and Granton. The maximum contribution from these sources to ground level annual mean concentrations is almost 2 μg m-3. The distributed boiler case for an emission factor of 60 g/GJ shows a maximum contribution from these sources to ground level annual mean concentrations is predicted to be almost 5 μg m-3.


Table 3.3 in the main text indicates that the current domestic heat demand satisfied by fossils fuels and electricity in Edinburgh is 13554.4 TJ per annum. Part of the existing housing will be demolished or substantially renovated and replaced by housing meeting the Council’s Priority Standards: it has been assumed here that 5% of the housing stock is replaced by 2020 (cf PB Power 5% replacement by 2025). The energy demands of the new houses will be less than the existing houses. Typical annual heat demands for UK households for space and water heating are 63.8 GJ per household23 compared to 30 GJ assumed here for new household heat demands. The overall heat demand will be reduced if demolished or renovated houses are replaced on a like for like basis by 359 TJ per annum. The annual heat requirement for the replacement properties will be 319 TJ, approximately 1.3% of Edinburgh’s current heat demand. If the heat demand for the new properties is met by biomass boilers with particulate emissions of 20 g/GJ of heat provided then the annual emission will be 6.37 tonnes. For an emission factor of 60 g/GJ, the emission will be three times greater. We have no information about where demolition and renovation will take place. The particulate emissions have therefore been allocated across the city in proportion to population based on 2001 census data. The contribution to annual mean concentrations from this source is predicted to be less than 0.1 μg m-3 for appliances with emission factors of 20 g/GJ. Figure A2.2 shows the predicted contribution from replacement houses fitted with biomass boilers with emission factors of 60 g/GJ. The predicted contribution remains less than 0.2 μg m-3 throughout Edinburgh, with the highest concentrations in the city centre.

23 http://stats.berr.gov.uk/energystats/ecuk3_3.xls http://stats.berr.gov.uk/energystats/ecuk3_6.xls



Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure A2.2: Modelled contribution to particulate matter concentrations from replacement housing developments in 2020 assuming an emission factor of 60 g/GJ.

Existing houses

The PB Power study Powering Edinburgh into the 21st Century24 suggested that there would be little conversion to biomass in the existing housing. However, Edinburgh has a range of housing types. Many of the more affluent areas such as Murrayfield and the Grange have large houses and villas with large gardens that may be particularly suitable for biomass conversion. Many of the houses in the Rural West Edinburgh area may also be suitable for conversion and may have access to inexpensive supplies of biomass. The suburban areas on the outskirts of the city may also have some potential. Areas of tenements in the most densely populated areas may be less suitable because of the space requirements. In this study, we have assessed the potential for conversion to biomass on the basis of population density throughout Edinburgh in 2001 as follows:

Less than 1000 inhabitants per km2 10% Between 1000 and 4000 inhabitants per km2 5% More than 4000 inhabitants per km2 1%

Overall, it is estimated that this would lead to conversion of 3.6% of the existing housing stock. It has also been assumed that biomass would then meet 3.6% of the current domestic heating demand for the city (481.8 TJ per annum) (2.0% of Edinburgh’s total heat demand). Assuming a particulate matter emission factor of 20 g/GJ for these installations provides an estimated annual emission of 9.63 tonnes. For an emission factor of 60 g/GJ, the emission will be three times greater. The contribution to annual mean concentrations from this source is predicted to be less than 0.1 μg m-3 for appliances with emission factors of 20 g/GJ. Figure A2.3 shows the predicted contribution from existing houses fitted with biomass boilers with emission factors of 60 g/GJ. The predicted contribution remains less than 0.2 μg m-3 throughout Edinburgh, with the highest concentrations in the suburbs surrounding the city centre.

24http://www.edinburgh.gov.uk/internet/Attachments/Internet/Environment/Sustainable%20Development/PB_POWER_Edinburghv2.pdf



Contribution, ug/m3

<0.1

0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure A2.3: Modelled contribution to particulate matter concentrations from replacement heating in existing houses in 2020 assuming an emission factor of 60 g/GJ.

Schools

The Edinburgh City Local plan identifies current school proposals that involve the development of new sites (Table A2.6).

Table A2.6: Current proposals for new school developments.

Proposal Site name Comments

SCH1 Craigroyston Community High School

Replacement school on brownfield site

SCH2 Tynecastle High School Replacement school on new site

SCH3 Boroughmuir High School Replacement school. Four storeys

SCH4 Portobello High School Replacement school

SCH5 Castlebrae Community High School Replacement school

SCH6 New Greendykes New primary school

SCH7 Waterfront Avenue New primary school

In addition, the Rural West Edinburgh Plan identifies the potential need for a new primary school at North Kirliston. The Council also has a number of proposals to rebuild schools on their existing sites. The Council has agreed a public private partnership to build eight schools by 2010. Biomass fuel has been identified as the preferred primary source of heating for seven of the schools as a solution to meeting the Council’s carbon target. The eighth school, Tynecastle, will be heated by the waste heat from the adjacent North British Distillery.



The gross internal floor area of primary schools in Edinburgh is 274184 m2: the floor area of secondary schools is 286545 m2. There were 24714 primary school pupils and 19454 secondary school pupils in 200725. Service sector fuel use for space and water heating in 2005 was typically 5327 GJ gross per hectare of floor space (BERR data). The annual heat demand for primary schools is thus 146.1 TJ: for secondary schools the annual heat demand is estimated to be 152.6 TJ. If this heat demand is met by biomass combustion with particulate emission factor of 20 g/GJ the annual emission from schools would be 6.0 tonnes. The total emissions have been allocated to each school in Edinburgh in proportion to the number of pupils. Each of the primary school boiler discharges was modelled as a point source with stack diameter 0.5 m and stack height 12 m above ground next to a rectangular building 10 m high and 30 m square. The discharge temperature was assumed to be 100oC and the discharge velocity was 1.4 m s-1. These conditions broadly correspond to a 400 kW boiler. Each of the secondary school boiler discharges was modelled as a point source with stack diameter 0.5 m and stack height 14 m above ground next to a rectangular building 10 m high and 30 m square. The discharge temperature was assumed to be 100oC and the discharge velocity was 2.6 m s-1. These conditions broadly correspond to a 700 kW boiler. Figure A2.4 shows the modelled contribution to particulate matter concentrations from biomass installations in all schools in Edinburgh assuming an emission factor of 60 g/GJ. The predicted contribution is less than 0.1 μg m-3 over most of the city, with higher concentrations in the vicinity of the schools. The maximum predicted contribution was less than 0.5 μg m-3. If the boilers operated with an emission factor of 20 g/GJ, the maximum predicted contribution was less than 0.2 μg m-3.


0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure A2.4: Modelled contribution to particulate matter concentrations from all schools in Edinburgh in 2020 assuming an emission factor of 60 g/GJ.

Business development

Table A2.7 shows the business opportunity sites identified in the Local Plans for Edinburgh City and Rural West Edinburgh. Service sector fuel use for space and water heating in 2005 was typically 5327 GJ gross per hectare of floor space (BERR data). The heat demands have been estimated on this basis. The total heat demand calculated for these developments is 1084 TJ, corresponding to 4.4% of Edinburgh’s current heat demand. It has been assumed

25 Scottish Government Statistics: http://www.scotland.gov.uk/Topics/Statistics/Browse/School-Education/TrendSchoolEstate



here as the maximum impact case that the whole of the heat demand for the new developments will be met by biomass combustion. Table A2.7 also shows the annual particulate emission for each development based on a particulate emission factor of 20 g/GJ. For developments with annual heat demands greater than 30 TJ, it has been assumed that the heat is supplied by biomass CHP with 50% thermal efficiency. It has also been assumed that the electricity generated is exported to the grid, rather than used for electrical heating within the development.

Table A2.7: Current proposals for new business developments.

Ref. Location Area (Ha)

Floorspace (m2)

Heat demand

(TJ)

Particulate emission

(kg/annum)

Centre for biomedical research, first phase

25 133500 71 2845 BUS1

Centre for biomedical research, 2nd phase 15 150000 80 3196

BUS2 Edinburgh Park 16 200000 107 4262

BUS3 Leith Eastern Industrial Area 20 200000 107 4262

ECON1 South Scotstoun, Queensferry 3.5 35000 19 373

ECON2 Ferrymuir, Queensferry 3.3 33000 18 352

ECON3 Clifton, Newbridge 7.2 72000 38 1534

ECON4 Cliftonhall Road, West Newbridge 2.3 23000 12 245

ECON5 Claylands, Newbridge South 31.1 311000 166 6627

ECON6 Cliftonhall Road, South Newbridge 0.9 9000 5 96

ECON7 Newbridge North 22.2 222000 118 4730

ECON8 Newbridge West 20.5 205000 109 4368

ECON9 Gogarburn 36.3 363000 193 7735

ECON10/HSG7 Port Edgar, Queensferry 7.9 79000 42 1683 Floorspace values in italics are estimated on the basis of a 2 storey building occupying half the available land area. Table A2.8 shows the modelled discharge point source discharge characteristics for each of the modelled developments. The thermal capacity of each unit was estimated assuming 30% utilisation for boiler units and 45% utilisation for CHP units. Discharge flowrates at capacity were then estimated assuming a theoretical air requirement of 0.3 kg air per MJ (Chemical Engineers Handbook), 6% excess air and discharge at 100oC. Stack diameters were then selected from the set {0.1 m, 0.2 m, 0.5 m and 1 m} based on the natural draught flowrates used in the development of the nomographs (Appendix 3). It was assumed that large installations would have multiple stacks with 1 metre stack diameter. Stack heights above ground were then estimated using the nomographs with the aim of limiting the maximum local contribution to annual mean particulate matter concentrations from each individual development to less than 1 μg m-3. It was assumed that each stack would discharge above a rectangular building 10 m high and 30 m square.



Table A2.8: Modelled discharge characteristics for business developments in Edinburgh.

Height (m)

Ref Location Easting (m)

Northing

(m)

Average emission

rate (g/s @20

g/GJ)

Thermal capacity

(MW) Diame

ter No.

units Discharge velocity 20 g/GJ 60 g/GJ

Centre for biomedical

research, first phase 29400 70300 0.090 10.0 1 2 4.59 26 37

BUS1 Centre for biomedical

research, 2nd phase 29700 70000 0.101 11.3 1 2 5.16 26 39

BUS2 Edinburgh Park 18000 71300 0.135 15.0 1 3 4.58 29 42

BUS3 Leith Eastern Industrial Area 28300 69200 0.135 15.0 1 3 4.58 29 42

ECON1 South Scotstoun, Queensferry 14000 77300 0.012 2.0 1 1 1.81 17 22

ECON2 Ferrymuir, Queensferry 12900 77300 0.011 1.9 1 1 1.70 17 22

ECON3 Clifton, Newbridge 12000 71800 0.049 5.4 1 1 4.95 21 30

ECON4 Cliftonhall Road, West Newbridge 11600 71800 0.008 1.3 1 1 1.19 15 20

ECON5 Claylands, Newbridge South 12000 71400 0.210 23.3 1 5 4.28 35 45

ECON6 Cliftonhall Road, South Newbridge 11700 71200 0.003 0.5 0.5 1 1.86 14 18

ECON7 Newbridge North 12200 73200 0.150 16.7 1 3 5.09 30 43

ECON8 Newbridge West 11900 72300 0.139 15.4 1 3 4.70 28 42

ECON9 Gogarburn 16600 72000 0.245 27.3 1 5 4.99 36 48

ECON10/HSG7 Port Edgar, Queensferry 11600 78700 0.053 5.9 1 1 5.43 21 31



Figure A2.5 shows the modelled contribution from new business developments in Edinburgh if they were heated by biomass installations with an emission factor of 20 g/GJ or 60 g/GJ. The predicted contribution for emissions factors of 20 g/GJ is less than 0.1 μg m-3 over most of Edinburgh, with higher contributions in the vicinity of the larger developments. The maximum contribution to annual mean concentrations was predicted to be 0.6 μg m-3. The predicted contribution for emissions factors of 60 g/GJ is more than 0.1 μg m-3 over a substantial part of Rural West Edinburgh, with higher contributions in the vicinity of the larger developments. The maximum contribution to annual mean concentrations was predicted to be 1.1 μg m-3. Emission factor of 20 g/GJ Emission factor of 60 g/GJ


0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5 Figure A2.5: Modelled contribution to particulate matter concentrations from biomass installations in new business developments in Edinburgh.

Shopping and related proposals

The Edinburgh Local Plans identify a number of shopping and related proposals (Table A2.9). Service sector fuel use for space and water heating in 2005 was typically 5327 GJ gross per hectare of floor space (BERR data). The heat demands have been estimated on this basis in Table A2.9. The total heat demand calculated for these developments is 75 TJ, corresponding to 0.3% of Edinburgh’s current heat demand. It has been assumed here as the maximum impact case that the whole of the heat demand for the new developments will be met by biomass combustion. Table A2.9 also shows the annual particulate emission for each development based on a particulate emission factor of 20 g/GJ.



Table A2.9: Current proposals for retail developments.

Ref Location Area (Ha) Floorspace (m2)

Heat demand

(TJ)

Particulate emission (kg/year)

CA1 St James Centre Retail 52500 28 559

S1 Wester Hailes Centre New superstore 10000 5 107

S2 Harvesters Way Commercial leisure development 10000 5 107

S3 Hermiston Gait Extend retail park 15000 8 160

S4 Niddrie Mains Road New retails units to extend local centre 2500 1 27

S5 Granton Waterfront Two new local centres 20000 11 213

S6 Leith Waterfront Two new local centres 20000 11 213

S7 Fountainbridge New local centre 10000 5 107 Table A2.10 shows the modelled discharge point source discharge characteristics for each of the modelled developments. The stack discharge characteristics were estimated following the method used for business developments, above.



Table A2.10: Modelled discharge characteristics for retail developments in Edinburgh.

Ref Location Eastin

g (m)

Northing (m)

Average emission rate, g/s

@20 g/GJ

Thermal capacity

(MW) Diameter

(m) No.

units Discharge

velocity (m/s)

Height (m) for 20

g/GJ

Height (m) for 60 g/GJ

CA1 St James Centre 25900 74200 0.018 3.0 1 1 2.71 18 24

S1 Wester Hailes Centre 19900 69900 0.003 0.6 0.5 1 2.06 14 18

S2 Harvesters Way 20000 69700 0.003 0.6 0.5 1 2.06 14 18

S3 Hermiston Gait 18300 71000 0.005 0.8 1 1 0.77 12 17

S4 Niddrie Mains Road 29300 71600 0.001 0.1 0.5 1 0.52 11 13

S5 Granton Waterfront 23700 77400 0.007 1.1 1 1 1.03 15 19

S6 Leith Waterfront 25900 77100 0.007 1.1 1 1 1.03 15 19

S7 Fountainbridge 24300 72800 0.003 0.6 0.5 1 2.06 14 18



The modelled contribution from emissions from new redevelopments fitted with biomass heating is generally less than 0.1 μg m-3 throughout Edinburgh except in the immediate vicinity of the retail developments.

Other institutions

Table A2.11 lists other institutions that may be suitable candidates for biomass heating. We have provisionally estimated the capacity of the boilers, and derived estimates of the annual heat demand and potential particulate emissions if biomass boilers or CHP were installed. The estimates have been based on 30% utilisation for biomass boilers and 45% utilisation for CHP. The total heat demand was estimated to be 564 TJ, approximately 2.3% of Edinburgh’s current heat demand. Table A2.11 also shows the annual particulate emission for each development based on a particulate emission factor of 20 g/GJ. For developments with annual heat demands greater than 30 TJ, it has been assumed that the heat is supplied by biomass CHP with 50% thermal efficiency. It has also been assumed that the electricity generated is exported to the grid, rather than used for electrical heating within the development.

Table A2.11: Other institutions viable for biomass heating.

Site Type Boiler

capacity (MW thermal

input) Utilisation TJ/annum

Particulate emission (kg/year)

Police headquarters Boiler 0.7 0.3 6.6 132 Scottish Executive CHP 3 0.45 42.6 1703

Western General Hospital CHP 3 0.45 42.6 1703 Edinburgh Royal Infirmary CHP 3 0.45 42.6 1703

TA Centre Boiler 0.7 0.3 6.6 132 Edinburgh College of Art Boiler 0.7 0.3 6.6 132

Scottish Agricultural College Boiler 0.7 0.3 6.6 132 Stevenson College Boiler 0.7 0.3 6.6 132

Newbattle Abbey College Boiler 0.7 0.3 6.6 132 Oatridge College Boiler 0.7 0.3 6.6 132

West Lothian College Boiler 0.7 0.3 6.6 132 Prison CHP 3 0.45 42.6 1703

Redford Barracks CHP 3 0.45 42.6 1703 Dreghorn Barracks CHP 3 0.45 42.6 1703

University of Edinburgh CHP 6 0.45 85.1 3406 Queen Margaret University CHP 3 0.45 42.6 1703

Napier University CHP 3 0.45 42.6 1703 Edinburgh University CHP 6 0.45 85.1 3406

Table A2.12 shows the modelled discharge point source discharge characteristics for each of the modelled developments. The stack discharge characteristics were estimated following the method used for business developments, above.



Table A2.12: Modelled discharge characteristics for other potential biomass installations in Edinburgh.

Site Type Easting (m)

Northing(m)

Average emission

rate (g/s @

20g/GJ)

Thermal capacity

(MW)

Stack Dia. (m)

No. units

Discharge velocity

(m/s)

Heightm

(for 20 g/GJ)

Heightm

(for 60 g/GJ)

Police headquarters Boiler 23500 74500 0.004 0.7 0.5 1 c 15 19 Scottish Executive CHP 26900 76700 0.054 6.0 1 1 5.50 22 31 Western General

Hospital CHP 24200 71200 0.054 6.0 1 1 5.50 22 31 Edinburgh Royal

Infirmary CHP 29200 70500 0.054 6.0 1 1 5.50 22 31

TA Centre Boiler 22000 69200 0.004 0.7 0.5 1 2.57 15 19 Edinburgh College of

Art Boiler 25200 73100 0.004 0.7 0.5 1 2.57 15 19 Scottish Agricultural

College Boiler 26500 70400 0.004 0.7 0.5 1 2.57 15 19

Stevenson College Boiler 19400 70400 0.004 0.7 0.5 1 2.57 15 19 Newbattle Abbey

College Boiler 33400 66100 0.004 0.7 0.5 1 2.57 15 19

Oatridge College Boiler 5500 73700 0.004 0.7 0.5 1 2.57 15 19 West Lothian College Boiler 4400 66500 0.004 0.7 0.5 1 2.57 15 19

Prison CHP 21300 71300 0.054 6.0 1 1 5.50 22 31 Redford Barracks CHP 22200 69500 0.054 6.0 1 1 5.50 22 31

Dreghorn Barracks CHP 22500 68300 0.054 6.0 1 1 5.50 22 31 University of Edinburgh CHP 26000 73300 0.108 12.0 1 2 5.50 28 39

Queen Margaret University CHP 20000 73300 0.054 6.0 1 1 5.50 22 31

Napier University CHP 22500 70100 0.054 6.0 1 1 5.50 22 31 Edinburgh University CHP 17500 69200 0.108 12.0 1 2 5.50 28 39

Figure A2.6 shows the modelled contribution from biomass installed in identified institutions in Edinburgh if they were heated by biomass installations with an emission factor of 60 g/GJ. The predicted contribution is more than 0.1 μg m-3 over a substantial part of the city, with higher contributions in the vicinity of the larger developments.



0.1 - 0.2

0.2 - 0.5

0.5 - 1

1-2

2-5

>5

Figure A2.6: Modelled contribution to particulate matter concentrations from biomass installations in other institutions in Edinburgh assuming an emission factor of 60 g/GJ.




Appendix 3: Air Quality Screening Tool for Biomass Combustion in Scotland A3.1 Introduction Local authorities are required to review and assess air quality in their areas against objectives set out in the Government’s Air Quality Strategy. Local authorities are then required to declare an AQMA where it is likely that the objectives will not be achieved. Technical Guidance LAQM.TG(03) provided advice on how to assess air quality. The Air Quality Strategy was revised in July 2007 and new Technical Guidance to support local authorities in their duties has been prepared and is currently the subject of consultation26. The Technical Guidance is supported by a technical report describing the development of the Guidance for biomass combustion27. The new Technical Guidance was prepared for application across the United Kingdom as a whole. Further guidance that is specific to Scotland is given in this section. The additional guidance takes into account the more stringent air quality objectives that apply in Scotland and different meteorology. The air quality objectives in Scotland for particulate matter are set out in the Air Quality Strategy 2007. They are:

• 18 μg m-3 as an annual mean for PM10 to be achieved by 31 December 2010 and maintained thereafter;

• 50 μg m-3 as a 24-hour mean for PM10 not to be exceeded on more than 7 times per year to be achieved by 31 December 2010 and maintained thereafter;

• 12 μg m-3 as an annual mean for PM2.5 to be achieved by 2020 and maintained thereafter; • an exposure reduction target of 15% reduction in PM2.5 annual mean concentrations at urban

background locations between 2010 and 2020. The objectives for nitrogen dioxide are:

• 40 μg m-3 as an annual mean to be achieved by 31 December 2005 and thereafter; • 200 μg m-3 as an hourly mean not to be exceeded on more than 18 days per year to be

achieved by 31 December 2005 and thereafter; The Technical Guidance for local authorities does not consider the exposure reduction target for particulate matter. The exposure reduction target is intended to be met at the national rather than local level: nevertheless, local authorities may wish to limit the contribution to ground level concentrations from biomass combustion sources in order to assist in meeting the national target. The Technical Guidance considers biomass combustion for:

• Domestic heating; • Service sector heating (commercial offices, communication and transport, education,

government, health, hotel and catering, retail, sport and leisure, warehouses); • Industrial combustion<20MW net thermal input (process heating, steam generation, electricity

generation and combined heat and power). Larger plant is regulated under the Pollution Prevention and Control (PPC) regime and is not considered here. Local authorities need to consider:

• whether each separate installation will lead to a local exceedence of the air quality objectives;

26 http://www.defra.gov.uk/corporate/consult/airqualitymanage-guidance/technical-guidance.pdf 27 http://www.airquality.co.uk/archive/reports/cat18/0806261519_methods.pdf


• whether several installations will combine to cause an exceedence of air quality objectives over a wider area.

Methods for assessing the local impact of individual installations are presented in Section A3.1. The methods consider whether the discharge stack is sufficiently tall to disperse the emitted pollutants. The methods cover service sector heating and industrial combustion. The height of chimney stacks for domestic appliances with less than 50 kW thermal input is covered by the Building Regulations. Methods for assessing the combined impact of multiple installations are presented in Section A3.2. The methods presented and are intended to provide an initial screening assessment to determine whether there is a risk of exceeding the objectives. The screening assessment is intended to provide a conservative overestimate of the potential impacts. More detailed assessment is required where the screening methods indicate that there is a risk of exceeding the objectives. The PPC regime covers a wide range of processes, including various combustion activities with less than 20 MW thermal input. The screening methods presented here are not sufficient on their own to meet the requirements of the PPC regime. The screening methods set out in the Technical Guidance are intended to assess whether there is a risk that the air quality objectives will not be met. When considering planning applications for new developments, local authorities may wish to impose more stringent limits on emissions in order to further protect the health of members of the public or to allow headroom for other future developments in the area.

A3.2 Individual installations Introduction Local Authorities require a simple tool for assessing whether a biomass combustion installation in the range 50 kW to 20 MW thermal will lead to pollutant concentrations exceeding the air quality objectives or will compromise the effectiveness of measures set out in their Action Plans. Technical Guidance TG(08) provides some simple nomographs for assessing whether the height of the chimney attached to a biomass appliance is sufficiently tall to disperse the pollutants emitted adequately. Further nomographs for application in Scotland are presented in this report. The development of these nomographs is described below. In some cases in large cities the background concentrations of pollutants already exceed the air quality objectives. In these cases, it will not be possible to install additional combustion plant without further increasing the pollutant concentrations. However, local authorities may choose to allow a small increase in pollutant concentrations locally in small areas in order that development is not unduly constrained. The provision of chimneys for biomass burners less than 50 kW thermal is covered by the Building Regulations. Development of the nomographs The dispersion model ADMS4 was used to predict ground level concentrations for a unit (1 g s-1) emission rate of pollutant from discharge stacks with heights in the range 10.6-40 m and diameters in the range 0.1-1m. ADMS is an up-to-date dispersion model widely used to assess the air quality impact of pollutant emissions. The discharge stack was assumed to be located at the centre of a 10 m cubical building. The discharge temperature was assumed to be 100oC, typical of biomass combustion appliances. Discharge velocities from the stacks were estimated on the basis that the appliances operate with forced draught just sufficient to overcome the pressure drops through the appliance. Table A3.1 lists the model runs and input values. Table A3.1 shows both the actual stack height above ground, C and the effective stack height, U:

for C<2.5H; otherwise U=C, where: H is the building height. )(66.1 HCU −=




Table A3.1: Actual and effective stack height modelling.

Run Stack height C (m)

Effective stack height U

(m) Stack diameter

(m) Discharge

velocity (m s-1)

A1_1 10.6 1 0.1 1.3 A2_1 11.2 2 0.1 1.3 A5_1 13 5 0.1 1.3

A10_1 16 10 0.1 1.3 A20_1 22 20 0.1 1.3 A40_1 40 40 0.1 1.3 A1_2 10.6 1 0.2 1.9 A2_2 11.2 2 0.2 1.9 A5_2 13 5 0.2 1.9

A10_2 16 10 0.2 1.9 A20_2 22 20 0.2 1.9 A40_2 40 40 0.2 1.9 A1_5 10.6 1 0.5 3 A2_5 11.2 2 0.5 3 A5_5 13 5 0.5 3

A10_5 16 10 0.5 3 A20_5 22 20 0.5 3 A40_5 40 40 0.5 3 A1_10 10.6 1 1 4.2 A2_10 11.2 2 1 4.2 A5_10 13 5 1 4.2 A10_10 16 10 1 4.2 A20_10 22 20 1 4.2 A40_10 40 40 1 4.2

The model was run with hourly sequential meteorological data for Edinburgh Airport, 2005 and 2006 with surface roughness 1 m locally and 0.1 m at the airport. The model was run with receptor locations on a 1 km square grid centred on the stack at 10 m intervals. Maximum annual mean and 99.8th percentile hourly mean concentrations were calculated. The emission rate, EA (g/s) that would lead to an increase in the maximum ground level concentration of 1 μg m-3 was then calculated28 (as the inverse of the maximum ground level concentration for unit emission). Cubic polynomial curves were fitted through the modelled data of the form:

dcxbxaxy +++= 23 where: x is log10(U); and y=log10(EA). Table A3.2: Shows the values of the constants a, b, c and d

28 The nomographs were developed based on a contribution of 1 μg m-3 to ground level concentrations. The allowable contribution to ground level concentrations from the plant will depend on the background concentration and on local authority policies. The procedures developed below allow these factors to be taken into account.


Table A3.2: Values of the constants a, b, c and d

Statistic Stack

diameter (m)

a b c d Range of

effective stack heights

(m) 0.1 0.6592 -0.8808 1.1678 -2.9726 1-40

0.2 0.6529 -0.8726 1.1353 -2.8755 1-40

0.5 0.5209 -0.5969 0.9404 -2.6473 2-40 Annual mean

1 0.3269 -0.1532 0.6738 -2.3851 5-40

0.1 0.1561 0.2070 0.3170 -3.5078 1-40

0.2 0.1574 0.1140 0.4086 -3.3572 1-40

0.5 0.1141 0.0483 0.6081 -3.1564 1-40

99.8th percentile of hourly means

1 0.5529 -1.7191 2.8338 -3.761 1-40 Figures A3.1 and A3.2 show nomographs based on the polynomial curve fits. Figure A3.1 shows the emission rates that correspond to an increase in maximum ground level annual mean concentrations of particulate matter or nitrogen dioxide of 1 μg m-3. Figure A3.2 shows the emission rate that corresponds to an increase in the 99.8th percentile oxides of nitrogen concentration of 40 μg m-3.




Figure A3.1: Emissions necessary to give an annual mean ground level concentration of 1 μg m-3 of oxides of nitrogen or particulate matter.

0

5

10

15

20

25

30

35

40

45

0.001 0.01 0.1 1

Emission rate, g/s

Effe

ctiv

e st

ack

heig

ht, m

0.1 m0.2 m0.5 m1 m


Figure A3.2: Emissions of oxides of nitrogen that will give a 99.8th percentile hourly mean concentration of 40 μg m-3.

0

5

10

15

20

25

30

35

40

45

0.01 0.1 1 10

Emission rate, g/s

Effe

ctiv

e st

ack

heig

ht, m

0.1 m0.2 m0.5 m1 m




Procedures The following sections describe how local authorities should use the nomographs to assess the potential impact on local air quality of proposed developments involving biomass combustion appliances. In order to use the nomographs, the local authority should estimate/derive the following information:

• Height of stack above ground; • Diameter of stack; • Dimensions of buildings within a distance from the stack of five times the stack height

above ground; • Description of the combustion appliance; and • Maximum rates of emission of particulate matter (PM10 and PM2.5) and oxides of

nitrogen when operating at capacity. The local authority may obtain details of the maximum thermal capacity of the appliance instead of the maximum rates of emission. Local authorities may then estimate rates of emission based on the Clean Air Act exemption limits or on the basis of emission factors provided by the EMEP/CORINAIR Emission Inventory Guidebook – 2006. In smoke-controlled areas, biomass burners require exemption under the Clean Air Act. Exempted appliances are required to emit less than 5 g/h particulate matter plus 0.1 g/h per 0.3 kW of heat output. The EMEP/CORINAIR Emission Inventory Guidebook – 2006 gives typical emission factors solid fuel appliances. These are summarised in the technical report supporting the new Technical Guidance. Note that for modern appliances with well–designed combustion the particles emitted are all thought to be less than 2.5 μm, hence the total particles, PM10 and PM2.5 emissions are equivalent. For traditional appliance designs this may not be so but is a conservative assumption in the absence of size fractionated measurements. In addition, local authorities should estimate background pollutant concentrations in their area from 1 km x 1 km maps provided for Local Authority Review and Assessment (http://www.airquality.co.uk/archive/laqm/tools.php?tool=background04) or from measurements at similar background locations. Where there are multiple stacks at the same site, a precautionary approach may be taken by assuming the total emissions (from all stacks) are released from the smallest stack. Where there are complex sites with many stacks, the nomographs are unlikely to be applicable, and authorities are advised to proceed to a more detailed assessment. PM10 The nomograph at Figure A3.1 may be used to assess whether the proposed biomass combustion installation is likely to lead to an exceedence of the annual objective for PM10 of 18 μg m-3 for 2010. First, calculate a “background-adjusted” emission rate using:

)18( GEEA −

=

where: E is the emission rate in g s-1 for the plant operating at capacity; and G is the annual average background concentration in μg m-3. If the actual stack above ground height is less than 2.5 times the height of the building to which it is attached or any other building within 5 times the stack height then it will be necessary to calculate an effective stack height. The effective stack height can be calculated from the following formula:

)(6.1 HUC −=


where C is the effective stack height, U is the actual stack height above ground, H is the height of the tallest building within a distance of 5 times the stack height. Otherwise, if the stack is more than 2.5 times the building height, then C=U. The nomographs cannot be used if the building height, H, is greater than the actual stack height. To use the nomograph, identify the line that corresponds to the diameter of the stack under consideration and locate the point on this line whose ordinate corresponds to the effective stack height. Read off the corresponding threshold emission rate on the horizontal axis and compare this with the “background-adjusted” emission rate. If the “background-adjusted” emission rate is greater than or equal to the threshold emission rate, the authority will need to proceed to a more detailed assessment. PM2.5 A similar procedure applies for PM2.5. The procedure uses the annual average nomograph Fig. A3.1. Firstly, determine the emission rate at capacity. The emission rate of PM2.5 may be conservatively assessed as equal to the PM10 emission. The background annual average PM2.5 concentration, G, may be determined from measurements at similar locations in the local authority area or neighbouring areas. The background adjusted emission rate for PM2.5 is calculated using:

)12( GEEA −

=

where: E is the emission rate in g s-1 at capacity; and G is the annual average background concentration in μg m-3. The 12 μg m-3 represents the annual average cap for PM2.5. Calculate the effective stack height as above. To use the nomograph, identify the line that corresponds to the diameter of the stack under consideration and locate the point on this line whose ordinate corresponds to the effective stack height. Read off the corresponding threshold emission rate on the horizontal axis and compare this with the “background-adjusted” emission rate. If the “background-adjusted” emission rate is greater than or equal to the threshold emission rate, the authority will need to proceed to a more detailed assessment. Nitrogen dioxide, annual mean A similar procedure applies for the annual mean nitrogen dioxide. The procedure uses the annual average nomograph Fig. A3.1. First determine the emission rate at capacity. The background concentration may be determined from 1 km x 1 km provided for Local Authority Review and Assessment (http://www.airquality.co.uk/archive/laqm/tools.php?tool=background04). The background adjusted emission rate for annual average oxides of nitrogen is calculated using:

)40( GEEA −

=

where: E is the emission rate in g s-1 at capacity; and G is the annual average background of nitrogen dioxide concentration in μg m-3. The 40 μg m-3 represents the annual average objective. Calculate the effective stack height as above. To use the nomograph, identify the line that corresponds to the diameter of the stack under consideration and locate the point on this line whose ordinate corresponds to the effective stack height. Read off the corresponding threshold emission rate on the horizontal axis and compare this with the “background- adjusted” emission rate. If the “background- adjusted” emission rate is greater




than or equal to the threshold emission rate, the authority will need to proceed to a more detailed assessment. Nitrogen dioxide, 1 hour average A similar procedure applies for the 1 hour average objective for nitrogen dioxide. The procedure uses the 99.8th percentile hourly nomograph Fig. A3.2. Firstly, determine the emission rate at capacity. The background concentration may be determined from 1 km x 1 km provided for Local Authority Review and Assessment (http://www.airquality.co.uk/archive/laqm/tools.php?tool=background04). The background adjusted emission rate for the hourly oxides of nitrogen is calculated using:

)2200(40

GEEA −

=

where: E is the emission rate in g s-1 at capacity; and G is the annual average background nitrogen dioxide concentration in μg m-3. The background concentration is multiplied by two to represent the typical ratio between the annual mean and the 99.8th percentile of 1 hour means taking into account the partial correlation between the variation in background concentration and the dispersion of a given plume which is then subtracted from the objective. Calculate the effective stack height as above. To use the nomograph, identify the line that corresponds to the diameter of the stack under consideration and locate the point on this line whose ordinate corresponds to the effective stack height. Read off the corresponding threshold emission rate on the horizontal axis and compare this with the “background- adjusted” emission rate. If the “background- adjusted” emission rate is greater than or equal to the threshold emission rate, the authority will need to proceed to a more detailed assessment.

An example A 500 kW net thermal input capacity pellet stove is installed in a building 15 m high. The stack height is 21 m and the stack diameter is 0.5 m. The pollutant emission rates are estimated from the factors for pellet stoves given in the technical report supporting the new Technical Guidance. These are 76 g/GJ for PM10, 76 g/GJ for PM2.5 and 90 g/GJ for oxides of nitrogen. The emission rates are then: 76 x 500 x 10-6 =0.038 g s-1 for PM10 and PM2.5, and 90 x 500 x 10-6=0.045 g s-1 for NOx. The background annual average nitrogen dioxide concentration is 35 μg m-3. The background annual average PM10 concentration is 15 μg m-3 and the annual average background PM2.5 concentration is 9 μg m-3. Table A3.3 shows the calculated background adjusted emission rates. The effective stack height is 1.66 x (21-15)= 10 m. Table A3.3 also shows the threshold emission rates determined for each pollutant metric from Figures A3.1 to A3.2. In each case the background adjusted emission rate is less than the threshold emission rate and so more detailed assessment is not required.


Table A3.3: Background adjusted emission rates and threshold emissions rates.

PM10 PM2.5 Annual man NO2 Hourly mean NO2

Emission rate, g/s 0.038 0.038 0.045 0.045

Background concentration, μg m-3 15 9 35 35

Background adjusted emission rate, g/s 0.013 0.013 0.009 0.014

Threshold emission rate, for 10 m effective

stack height, g/s 0.018 0.018 0.018 0.16

A3.3 Combined impacts Introduction A number of local authorities have expressed concern that the effects of many small biomass combustion installations that are individually acceptable could combine and lead to unacceptably high particulate matter concentrations. The new Technical Guidance provides a simple nomograph for assessing the combined impact of many installations. This section provides additional nomographs that take account of the meteorological conditions in Scotland and the more stringent air quality objectives. Dispersion modelling The dispersion model ADMS4 was used to predict the maximum annual average ground level concentration resulting from a uniform emission rate applied over areas of 1 km2, 4 km2 and 16 km2 representing villages, small towns and relatively large towns respectively. Each area was represented as a square volume source, 10 m deep. The model used hourly sequential meteorological data for Edinburgh Airport for 2006. The surface roughness of the modelled area was assumed to be 1 m. Urban heat island effects were taken into account by setting a lower limit of 20 m for the Monin-Obukhov length for the small and large towns: no restriction was applied for the “village”. The maximum predicted annual mean concentrations for a uniform emission rate of 1 g s-1 km-2 were 11.7 μg m-3 for the “village”, 13.0 μg m-3 for the “small town” and 16.3 μg m-3 for the “large town”. On this basis it was calculated that annual emissions of 2.69 tonne km-2, 2.43 tonne km-2 and 1.93 tonne km-2 would result in an increase in the annual mean concentrations of 1 μg m-3 in the “village”, “small town” and “large town” respectively. Estimating emissions The new Technical Guidance provides a method for estimating emissions from domestic and service sector biomass combustion based on the number of households and the area of service sector floorspace heated by solid fuels in an area for a range of combustion technologies. Table A3.4 lists the estimated annual emissions per household or hectare of service sector floorspace.




Table A3.4: Estimated annual emissions per household or hectare of service sector floorspace.

Emissions per household (kg year-1)

Emissions per hectare of service sector

floorspace (kg year-1) Appliance type Fuel

PM10 PM2.5 PM10 PM2.5

Coal 20.00 20.00 1670 1670 Fireplace

Wood 27.43 27.12 2291 2264

Coal 27.27 27.27 2277 2277

Solid smokeless fuel 6.06 6.06 506 506 Stove

Wood 25.84 25.84 2157 2157

Coal 14.55 13.33 1215 1113 Advanced stove

Wood 7.66 7.66 639 639

Pellet stove Wood 4.07 4.07 340 340

Coal 23.03 21.82 1923 1822

Solid smokeless fuels 6.06 6.06 506 506 Boiler<50 kWth

Wood 15.15 15.15 1265 1265

Coal 962 860

Solid smokeless fuels 405 405 Boiler > 50 kW th and < 1MW th

Wood 1074 1074

Coal 385 364 Boiler>1MW th

Wood 300 291

Coal 8.49 7.88 708 658 Advanced manual boiler

Wood 2.42 2.42 202 202

Coal 4.61 4.36 385 364 Advanced automatic boiler

Wood 3.54 3.54 295 295

Coal 30 25 Boiler, with fabric filter<20 mg/Nm3 TSP Wood 31 27

Coal 127 61 Older boiler with fabric filter or electrostatic precipitator <100

mg/Nm3 TSP Wood 112 54

Coal 304 177 Boiler with uncontrolled multicyclone Wood 313 246

Best available domestic Wood 1.07 1.07


Method Solid fuel burning tends to be concentrated into small areas or estates, which generally cover less than 1 km2. The procedure in the new Technical Guidance requires authorities to identify the area with the highest density of solid fuel burning houses and then to estimate the number of houses burning coal, smokeless fuel or wood within a 500 m x 500 m grid square. The proportion of space in the 500 m x 500m square not occupied by solid fuel burning houses is also required, together with the annual mean background concentration. The procedure is:

1 Identify the areas with the highest densities of houses and service sector appliances burning solid fuels.

2 Identify the types of solid fuel appliance used in each area from the list in Table A3.4.

3 Count the numbers of each domestic heating appliance type in the identified 500 x 500 m squares. Estimate the floorspace occupied in the service sector in each of the identified 500 m x 500 m squares for each of the identified types of solid fuel burning plant.

4 Multiply the number of houses for each appliance type by the annual household emission shown in Table A3.4. Sum the emissions from each of the domestic appliance types to give the total annual domestic emission from the 500 m x 500 m square.

5 Multiply the service sector floorspace (in hectares) for each appliance type by the annual service sector emission per hectare. Sum the emissions from each of the service sector appliance types to give the total annual service sector emission from the 500 m x 500m square. Add the service sector emissions to the domestic emissions to give the total emissions from the square.

6 Estimate the fraction of space in the 500 m x 500 m square occupied by solid fuel burning premises or domestic properties. Divide the annual emission by the fraction occupied by solid fuel burning to give the emissions density for the square (kg emissions per 500 m x 500 m area).

7 Figure A3.3 describes the annual emissions from a 500 m x 500m square (the threshold emissions density) that may give rise to an exceedence of the annual mean objective for PM10 for a particular estimated background PM10 concentration. If the emissions density from the square exceeds the threshold emissions density shown in Fig. A3.3, then the authority will need to proceed to a detailed assessment.

8 Figure A3.4 describes the annual emissions from a 500 m x 500m square (the threshold emissions density) that may give rise to an exceedence of the annual mean cap for PM2.5 for a particular estimated background PM2.5 concentration. If the emissions density from the square exceeds the threshold emissions density shown in Fig. A3.4, then the authority will need to proceed to a detailed assessment.




Figure A3.3: Threshold emissions density of emissions from a 500 m x 500 m area that may produce an exceedence of the daily average objective for PM10.

Figure A3.4: Threshold emissions density of emissions from a 500 m x 500 m area that may produce an exceedence of the annual average cap for PM2.5.

0

1000

2000

3000

4000

5000

6000

10 11 12 13 14 15 16 17 18 19

Background PM10 concentration, ug/m3 gravimetric

Ann

ual e

mis

sion

, kg

VillageSmall townLarge town

0

1000

2000

3000

4000

5000

6000

4 5 6 7 8 9 10 11 12 13

Background PM2.5 concentration, ug/m3 gravimetric

Ann

ual e

mis

sion

, kg

VillageSmall townLarge town


Example Consider a 500 m x 500 m square containing a new 6 hectare development of 400 houses on the outskirts of a large town. The houses are fitted with advanced automatic wood pellet boilers. The new development adjoins an 8 hectare older estate. The older estate has largely converted to gas heating but there remain 50 houses that use conventional boilers burning coal. The 500 m x 500 m square also contains a school with floor area of 0.2 hectares in a plot of 1 hectare: the school is heated by means of a wood-burning advanced automatic boiler. There is also a public house with floor area of 0.1 hectare in a plot of 0.5 hectare; the public house is heated by open wood fires. The remaining part of the 500 m x 500 m square does not contain premises burning solid fuels. The total emissions of PM10 from the residential area is: 400 x 3.54+50 x 23.03=1416+1152=2568 kg. The total emissions of PM10 from the school and the public house are: 0.2 x 295 + 0.1 x 2291 =59 +229 =288 kg. The total emissions from all solid fuel sources are then 2568 + 288 =2856 kg. The area of the 500 x 500 m square occupied by solid fuel heated premises is: 6+8+1+0.5=15.5 hectares. Thus the fraction occupied is 9.5/25 =0.62. The emissions density is then 2856/0.62=4606 kg /year. The background PM10 in the area is estimated from the national maps to be 16 μg m-3. From Figure A3.3, the threshold emission density is 950 kg/ year. In this case, the calculated emissions for the 500 m x 500 m square are more than the threshold and a detailed assessment is required.


The Gemini Building Fermi Avenue Harwell International Business Centre Didcot Oxfordshire OX11 0QR Tel: 0845 345 3302

Fax: 0870 190 6318

Glengarnock Technology Centre Caledonian rd Lochshore Business Park Glengarnock Ayrshire KA14 3DD Tel: 0870 190 5150

Fax: 0870 190 5151

E-mail: [email protected],uk www.aea-energy-and-environment.co.uk

© Crown copyright 2008

This document is also available on the Scottish Government website:

www.scotland.gov.uk

RR Donnelley B58366 11/08

Further copies are available from

Blackwell’s Bookshop

53 South Bridge

Edinburgh

EH1 1YS

Telephone orders and enquiries

0131 622 8283 or 0131 622 8258

Fax orders

0131 557 8149

Email orders

[email protected]

w w w . s c o t l a n d . g o v . u k

from Wood-Burning Biomass Boilers

Documents

Transcript of from Wood-Burning Biomass Boilers