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Biomass heatingA practical guide or potential users
In-depth guide CTG012
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www.carbontrust.co.uk
ContentsPreface 01
Executive summary 02
Biomass as a low carbon energy source 02
The need or biomass heating 02
Biomass uels and heating systems 03
Implementing a successul biomass system 03
Part 1 Introduction 07
1.1 What is biomass? 08
1.2 Why is biomass a renewable and low carbon
source o uel? 08
1.3 Why use a biomass heating system? 09
Part 2 Technical manual 15
2.1 Biomass uels 16
2.2 Biomass heating systems 36
Part 3 Implementation guide 49
3.1 Initial assessment 52
3.2 Detailed easibility 53
3.3 Procurement and implementation 72
3.4 Operation and maintenance 80
Glossary 84
Appendix A Conversion factors 86
Appendix B Basic calculations 88
The Carbon Trust would like to acknowledge the support and input o the ollowing organisations and individuals
in the preparation o this guide:
Biomass Energy Centre, Black & Veatch Ltd., Buro Happold Ltd., Peter Coleman (AEAT Ltd.), Department o Energy
and Climate Change, Econergy Ltd., Forest Fuels Ltd., Forestry Commission, Andy Hall and Geo Hogan (Forestry
Commission), Anthony Haywood (Cwm Rhonda NHS Trust), Imperative Energy Ltd., Invest Northern Ireland,Richard Landen, Ali Nicol, Walter Poetsch (BSRIA), RegenSW, Gideon Richards (CWP Ltd.), Andrew Russell (Mercia
Energy), Scottish Government, South West o England Regional Development Agency, Daniel Sullivan (Optimum
Consulting), Welsh Assembly Government and Wood Energy Ltd.
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01Biomass heating: A practical guide or potential users
Recognising the potential impact o biomass heating
in this range or commercial and industrial applications,
the Carbon Trust launched the Biomass Heat Accelerator(BHA) in 2006. By working with existing biomass heating
projects across the UK, the BHA has identied that a lack
o customer knowledge and understanding o biomassheating technology is a signicant barrier to wider uptake.
This guide, prepared with the assistance o Black
& Veatch Ltd., is the rst major publication rom theBiomass Heat Accelerator and is intended to provide
practical guidance to businesses and public sector
organisations considering using biomass as an alternative
source o heating or space, hot water and/or processheat. The guide ocuses on existing, conventional
biomass combustion equipment that uses solid uels
such as wood chips, pelletised biomass uels and straw.However, much o the inormation in this guide will also
be o relevance to those involved with other types o
biomass projects (e.g. biomass CHP schemes).
The rst section o the guide introduces the concept
o biomass as a low carbon source o uel and the key
benets o its use. It also covers some o the high-level
policy and market aspects o biomass use in the EU andthe UK.
The second section provides a detailed technical
overview o the properties o biomass uels and typicalbiomass heating equipment.
The third section contains a process guide covering
details o the steps required to take a biomass system
rom initial concept to ull implementation. Althoughthis is not intended to be denitive, and individual
circumstances and projects will vary, the section is
intended to help potential site owners approach suchprojects in a logical, structured manner.
The inormation and processes laid out in this guide will
also help organisations adopt best practice approaches
and avoid common errors when installing biomassheating systems. The guide should help users to design,
procure, implement and operate successul, cost-eective
biomass heating solutions and achieve signicant
carbon savings.
Throughout this guide, the term site owner is used
to mean an individual or organisation considering
implementing a biomass heating system at a specicsite. However, the guide will also interest project
developers, energy managers, those acting on behal
o clients to help them speciy and procure biomass
heating systems or other interested stakeholders such
as government bodies.
Preface
1 http://www.carbontrust.co.uk/publications/publicationdetail?productid=CTC512
The Biomass Heat Accelerator
The Biomass Heat Accelerator is one o the
Carbon Trusts Technology Acceleration projectswhich aims to accelerate the uptake o this low
carbon source o energy.To achieve this, the Biomass Heat Accelerator isworking with a range o the UKs leading installers
and manuacturers o biomass heating equipment
to reduce the total cost o projects. The Biomass
Heat Accelerator is also working to reduce risksin the uel supply chain through quality assurance
and inormation provision.
More broadly the aim o the project is to increaseawareness and understanding o biomass heating
technology amongst the customer base as a lack
o this presently restricts wider market uptake.Visit: www.carbontrust.co.uk/biomass or more
inormation on the Biomass Heat Accelerator.
In 2005, the Carbon Trusts Biomass Sector Review1 highlighted the signifcant
potential o biomass heating in the UK. It showed that carbon savings o up to20 million tonnes o CO2 per year could be achieved using UK biomass resources
alone. It also identifed that using biomass or heating typically gives the most
cost-eective carbon savings o all uses o biomass and that this is particularly
the case or small-to-medium scale applications (100 kWth-3MWth).
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02 Executive summary
Biomass as a low carbon energy sourceBiomass is a orm o stored solar energy and is available
in a number o dierent orms. These include wood,straw, energy crops, sewage sludge, waste organic
materials and animal litter.
Although burning biomass releases carbon dioxide
to the atmosphere, this is oset by the carbon dioxideabsorbed in the original growth o the biomass, or
captured in the growth o new biomass to replace the
materials used. As a result, using biomass or heatingresults in very low net liecycle carbon emissions
relative to conventional sources o heating, such as gas,heating oil or electricity.
The need or biomass heating
Heat in all its orms presently accounts or nearly hal
o the UKs carbon emissions2. The UK has a legal
requirement to reduce carbon emissions by at least26% by 2020 and 80% by 2050 (against a 1990 baseline)
under the Climate Change Act3. Meeting these targets
will require a major shit away rom ossil uel heating
systems to lower carbon orms o heating.
In June 2008, the Governments Renewable EnergyStrategy consultation proposed that under one possible
scenario 14% o the UKs heating may need to comerom renewable sources by 2020 or the UK to meet its
share o the EU 2020 target or total renewable energy.
Given that less than 1% o UK heat demand is currentlymet by renewable sources, this implies a dramatic and
rapid transormation in the way heat is provided over the
next decade. To help deliver this step change in renewable
heat the Government took powers in the 2008 EnergyAct to establish a Renewable Heat Incentive (RHI) to
give nancial support to those generating renewable
heat. An overview o the RHI appears on page 66.O all possible renewable heating solutions, biomass
has the potential to deliver some o the most signicant
and cost-eective carbon savings, particularly orcommercial and industrial applications. In addition to
carbon savings, biomass heating also oers signicant
benets or users, including operational uel cost
savings and reduced uel price volatility. It can alsostimulate local economic activity by creating uel
supply chains and make use o resources that would
otherwise be treated as waste and sent to landll.
Executive summary
2 http://renewableconsultation.berr.gov.uk/consultation/chapter-4/executive-summary/3 http://www.dera.gov.uk/environment/climatechange/uk/legislation/index.htm
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03Biomass heating: A practical guide or potential users
Biomass uels and heating systemsBiomass heating is a mature, proven technology and
has been used successully or many years in countriessuch as Austria, Finland and Denmark. The two key
elements o a biomass heating solution are the uels
and the heating system.
The most commonly used sources o biomass heatinguels are virgin wood, certain energy crops, industrial
wood residues and certain agricultural residues. Biomass
uels are typically delivered as woodchips or woodpellets, but can also be in other orms such as logs or
straw bales. Fuel is normally provided by one or morededicated suppliers, but on-site materials can also beused in some situations, such as on arms.
The key characteristics o a biomass uel include its
moisture content which aects its energy content (the
caloric value), and the particle size/grade. Factors whichaect uel costs include the type o uel and its associated
market availability, the quality o the uel, the orm the
uel is delivered in and the proximity o the uel sourceto the point o use.
The heating system itsel consists o biomass boiler
plant, ancillary equipment (such as control systemsfues and pipe work), and inrastructure to receive andstore uel and transer it to the main boiler unit. Fuel
can be stored in various ways, such as dedicated storage
acilities (either above or below ground), integratedacilities within existing buildings, or in removable
storage containers.
Biomass plant can vary rom small, manually edsystems with ew controls, to ully automatic systems
with advanced controls and remote monitoring. The
types o plant available range rom moving grate, plane
grate, stoker burner and batch-red systems with thechoice o system dependent upon uel grade and type
and the degree o automation required, with costs
varying accordingly.
Biomass heating equipment is best suited to operating
relatively continuously. This means that a heat store
and/or back-up plant are useul means o smoothing
demand. Biomass systems are also typically physicallylarger than equivalent ossil-uel systems.
Implementing a successul biomasssystem
The Carbon Trusts experience o working with existing
biomass heating installations has shown that there iscurrently a wide variation between common practice
and best practice.
In order to successully design and deliver a highperorming, cost-eective biomass heating solution it is
essential that site owners ollow a structured approach
to system implementation.
The key phases o this approach are as ollows:
Initial assessment
In this phase the aim is to understand quickly whetherbiomass is likely to be an appropriate, alternative
heating solution or the site beore embarking
on a detailed easibility study and engaging with
potential suppliers. This phase typically involvesa basic assessment o site suitability, a basic
economic appraisal and a review o other potential,
non-nancial benets.
Detailed easibility
In this phase the aim is to acquire all the necessary
inormation on which to make a rm decision on
whether to proceed with a project. This includes: adetailed assessment o site heat demands, required
system characteristics, detailed capital and operating
costs, logistics, uel availability, uel storage, andany required permits/consents.
Procurement and implementation
The ultimate aim o this phase is to successully
install, commission and hand over a ully operational
biomass heating system. This involves speciying,
tendering or and implementing a biomass heatingsystem and associated uel contracting.
Operation and maintenance
This is an ongoing phase which involves uel quality
monitoring, system perormance monitoring androutine, planned maintenance.
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04 Executive summary
Structure o the guide
Part 1 Introduction
An introduction to biomass and biomass heating;the rationale underpinning biomass use; anintroduction to uel supply operations and biomassheating technology.
Part 2 Technical manualCovers detailed aspects o the uel used in biomassheating and delivery/storage methods. Describesthe basic components o a biomass heating systemincluding outline design and sizing strategies/integration options.
Part 3 Implementation guide
A summary guide to conducting a detailed easibilitystudy or a biomass system, implementing a project
and planning operation and maintenance.
Page 07
Page 15
Page 49
About this guide
This guide has been prepared with input rom some othe UKs leading experts in biomass technologies, and
brings together a host o issues that potential users willwant to consider. It covers a wide range o topics rom
choice o uels to contracting structures. Inevitably it
cannot be more than an introduction to the considerationsapplicable to each dierent subject, or exhaustive in
its treatment.
The Carbon Trust recommends, and this guide assumes,that prospective users will take advice on their specic
needs and circumstances rom proessionals in the eld,
including not only technical consultants and installers,
but legal, planning and other specialists as required.
The guide is designed to assist readers in navigatingthrough what can appear to be a complex technology
and engaging eectively with expert advisers to ensure
successul implementation.
This guide does not purport to give detailed Health &
Saety inormation, and accordingly should be read in
conjunction with specic installation advice.
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05Biomass heating: A practical guide or potential users
Stages in a biomass heating project implementation
Initialassessment
Assess basiceconomics
Assess basic sitesuitability
Detailedeasibility
Determine site heatdemand(s) and demand
prole
Assess necessarypermits and consents
required
Assess spatialconstraints which wouldinfuence system design
Determine plant size
and boiler plant designoptions
Perorm ull economicappraisal
Determine uelavailability, type,
sourcing, price andquantities required
Procurement andimplementation
Establish preerred
contract type
Detailed systemdesign
Apply or externalnancial assistance
i available
Installation/construction works
Commissioningand training
Issue tenders orproject
Prepare systemspecication
Review tender returnsand select preerred
bidder
Speciy and procureuel
Apply or/acquire anynecessary permits and
consents required
Operation andmaintenance
Standard operationalmaintenance regime
Annual maintenance
Ongoing perormancemonitoring
Decision tocarry out detailed
assessment
Initial decisionto investigate
biomass heating
Decision topurchase biomassheating equipment
Handover
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07Biomass heating: A practical guide or potential users
This section o the guide introduces the concept o biomass as an alternative
uel or heating. It describes the carbon cycle and the sustainability o biomass
as a uel. It also gives a basic introduction to the technology, the state o
the current market in the UK and the EU, and general aspects o using this
source o renewable, low carbon energy.
Part 1 Introduction
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08 Introduction
1.1 What is biomass?
Biomass is organic matter o contemporary biologicalorigin (i.e. that was living recently) such as wood, straw,
energy crops, sewage sludge, waste organic materials,and animal litter. It can be viewed as a orm o stored
solar energy which is captured by the organic matter
as it grows. This energy is released by combustion(burning) or ermentation and distillation (to produce
liquid transport uels). Biomass materials used as uel
sources can provide heat, electrical and motive power.
Biomass already makes an important contribution tothe UKs renewable energy supply, representing 82%4
on a primary input basis in 2006 (1.9% o total primary
energy consumption). Biomass has considerableuntapped resource potential and, in uture, could play
a signicant role in helping the UK to meet a range o
existing renewable energy and greenhouse gas (GHG)reduction targets.
Combusting biomass uels (such as wood, straw or
energy crops to produce heat or hot water and to raise
steam or space or process heating applications) iscurrently recognised5,6 as being one o the most cost-
eective ways o using biomass or energy conversion
purposes, in terms o the cost per tonne o carbon
emissions avoided.In the context o small heating systems, the term
biomass normally reers to wood-based uels such aswoodchips or wood pellets, but it can also include other
materials such as straw bales and more conventional
wood logs.
1.2 Why is biomass a renewable and
low carbon source o uel?The sun is the primary source o energy contained
within all biomass uels its energy is captured andstored via the process o photosynthesis. This energy
can be released and used (e.g. by combustion). When
this occurs, CO2 and other by-products o combustion
are also released. However, the CO2 released is largelyoset by that which was absorbed in the original growth
o the biomass, or which will be captured in the growth
o new biomass to replace the biomass being used(as illustrated in Figure 1).
Consequently biomass is considered to be a low
carbon technology i the material is derived romsustainable sources.
In contrast, when ossil uels are combusted, they release
CO2 that was captured by photosynthesis millions oyears ago, and it is the release o this ossil CO2, as
opposed to contemporary biogenic CO2, that is the
major contributor to global climate change.
Although the CO2 resulting rom the combustion obiomass can be recaptured by the new growth o
sustainable biomass, some net emissions still result
rom the cultivation, harvesting, processing andtransportation o the uel, and the manuacture and
operation o the necessary equipment (e.g. the biomass
plant). These processes consume ossil uels and thus
lead to some CO2 emissions.
Figure 1 A typical biomass carbon cycle
Atmospheric carbon dioxide, water and sunlight
Carbon releasedback into the atmosphere Converted into new plant material
through photosynthesis
Harvested and burnt
4 BERR (July 2007) UK Energy in Brie(includes all biomass sources). http://www.berr.gov.uk/whatwedo/energy/statistics/publications/in-brie/page17222.html5 The Carbon Trust (October 2005) Biomass Sector Reviewor the Carbon Trust. www.carbontrust.co.uk/biomass6 Dera (May 2007) UK Biomass Strategy. http://www.dera.gov.uk/environment/climatechange/uk/energy/renewableuel/pd/ukbiomassstrategy-0507.pd
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09Biomass heating: A practical guide or potential users
Although there are some net CO2 emissions rom using
biomass, the considerable body o publicly available
research indicates that using solid biomass or heatingtypically gives reductions in carbon emissions o around
90% relative to using ossil uel heating systems, when
these net emissions have been taken in to consideration.
Table 1 shows the typical ranges o carbon emissionsper unit o power which are achieved or biomass when
used or heating and electricity conversion, relative to
conventional uels. These gures include raw materialsupply, production, transport, energy generation and
eventual disposal.
However, some emissions comparisons between
biomass and conventional uels, oten understate the
carbon-saving benets that biomass technologies oerrelative to ossil uels. Unlike the gures in Table 1, they
oten ail to account or the embodied and operational
carbon emissions associated with the upstreamactivities o exploration, extraction, transportation and
processing o ossil uels, whereas these are explicitly
accounted or in any liecycle assessment. When the
ull upstream emissions associated with ossil uels
are also taken into account, the net carbon emissionso most biomass heating scenarios are even lower.
1.3 Why use biomass heating systems?
Using biomass is one o the only cost eective andpractical ways to provide space heating, hot water
and process heating/steam rom a low carbon source.Also, using biomass sources or heating provides more
cost-eective carbon savings than or other uses (e.g.
or electricity or transport uels). It typically oers thehighest carbon savings per unit mass o biomass, and
the highest carbon savings that can be obtained by
using a unit o land to grow biomass8.
While organisations may choose to implement a biomassheating system or a number o dierent reasons, the
major drivers are as ollows:
1) Signicant carbon savings. Biomass heating systemscan play a major role in reducing an organisations carbon
ootprint. Many organisations now have commitments
or requirements to reduce their overall emissions andimprove their environmental perormance implementing
a biomass heating system could help to do this.
2) Operational cost savings. The costs o biomass uels
are typically lower than the ossil uel being displacedand biomass heating systems can thereore provide
attractive operational cost savings. The scale o savings
depends on the price o the ossil uel being replaced and
the cost o the biomass uel used. On a unit cost-basis,biomass uels can be cheaper than many ossil uels
commonly used or heating. Cheaper uel translates into
lower running costs, and hence annual savings whichover time help pay back the higher capital outlay on the
biomass system (compared to ossil uel systems). When
replacing electric, LPG or heating oil systems, the paybackon capital can be very rapid (in some cases
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10 Introduction
4) Wider sustainable development benets. Fuels used
typically with biomass heating systems tend to have
diverse and localised uel supply chains. Using biomassuels or heating can have positive side-benets along
this supply chain such as improving the biodiversity
o existing woodlands9 and providing opportunities orrural employment and economic diversication.
5) Resources diverted rom landll. Using certain
biomass resources as uels can divert them rom
becoming wastes and being sent to landll. Currentlyc.10 million tonnes o waste woods are produced each
year10, the majority o which goes to landll. Some
organisations produce co-products such as wood o-cuts,
sawdust and tree-surgery residues (arboriculturalarisings) that can be used as a biomass uel. Disposing
o such wastes normally has a considerable associated
cost and using wastes as uels can thereore also bringsignicant nancial benets11.
6) Reduced exposure to climate-change related
legislation. Biomass uels do not register as part o anorganisations overall carbon emissions (or ossil uel
consumption), thus reducing exposure to the Carbon
Reduction Commitment (CRC) and the EU EmissionsTrading Scheme (EU ETS), i the organisation is subject to
these schemes. A biomass heating system can also help
organisations to meet their Climate Change Agreements(CCAs) by reducing emissions o greenhouse gases andconsumption o ossil uels.
7) Improved energy perormance ratings or buildings.
Using biomass heating equipment in new orreurbished building stock could help to improve its
overall environmental/energy perormance. As such,
it could help achieve higher ratings in such schemes asBREEAM (Building Research Establishment Environmental
Assessment Method) and the Code or Sustainable
Homes. Installing a biomass heating system in a new or
reurbished building could also help it to achieve lowercarbon emissions as represented in an EPC (Energy
Perormance Certicate) and DEC (Display Energy
Certicate). Biomass systems can also assist compliancewith Part L o the building regulations and Merton
Rule12 requirements.
In summary, within the context o changing energyprices and the need to reduce carbon ootprints while
also diversiying sources o energy, biomass heating
oers a number o advantages which merit its urtherinvestigation by interested organisations.
9 Forestry Commission (2007) A Wooduel Strategy or England. http://www.orestry.gov.uk/england-wooduel10 Dera (2008) Waste Wood as a Biomass Fuel. http://www.dera.gov.uk/environment/waste/11 Using biomass resources that are (or could be seen to be) wastes can be aected by waste legislation and potential users should read section 3.2.5
in detail beore pursuing this route.12 The Merton Rule is a planning policy, pioneered by the London Borough o Merton, which requires the use o renewable energy on-site to reduce
annual carbon dioxide (CO2) emissions in the built environment and is now in use by many local authorities around the UK.
Case study:
Bell Bros Nurseries Ltd
Bell Brothers Nurseries Ltd is one o the UKs market
leaders in growing bedding plants and supplies
to all parts o the market including DIY stores,
supermarkets, wholesalers and local councils. Theenterprise has over 50,000m2 o modern, automated
glasshouses which require year-round heating to
maintain optimum growing conditions. Historicallythe main heating uel had been heating oil. Rises
in the price o this uel and the associated increase
in running costs led to the need to investigate other
alternatives. The nurserys management beganresearching the viability o biomass as an alternative
heating solution to reduce heating costs in 2004 /5.
Ater a detailed easibility study, a decision wastaken to install a 2MWth biomass boiler in October
2007 which is expected to deliver approximately
60-70% o the annual heating requirement to33,000m2 o glasshouses. The boiler is o a moving
(reciprocating) grate design and is expected to
consume c.2000-2500 tonnes o wood-chip (or
equivalent) per annum. The moving grate design waschosen to enable the system to burn a wide variety o
dierent types o potential biomass uels (including
lower quality woodchips, miscanthus grass,agricultural residues, and uels with high moisture
contents up to 55-60%). This gives Bell Brothers
Nurseries considerable uel fexibility and could
allow them to take advantage o very low cost uels.
The project received a capital grant which amounted
to 17.5% o the total capex. Depending on ossil uel
prices, the project is expected to achieve payback in4 years.
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11Biomass heating: A practical guide or potential users
Biomass heating technology overview
A biomass heating system is any heating system that
primarily uses biomass as a uel (some systems canalso dual-re with a ossil uel to meet peak demands,
or or back-up).
Biomass heating systems can be used or space heatingo buildings, hot water production, steam production,
or any combination o these. They can be used at
almost any scale, rom domestic (c.10kWth) throughto light commercial (c.50kWth to several MWth), to
industrial or district heating systems (up to hundreds
o MWth
). While this guide ocuses on the scale range o
100kWth 3MWth, most biomass heating systems havestrong similarities above and below this size range.
The key elements o a whole biomass heating
solution are:
Fuel delivery rom a uel supplier.
Fuel reception, storage, and extraction rom storageto the boiler unit.
A specialised biomass boiler unit.
Ancillary equipment: fue (chimney), ash extractionmechanism, heat storage, connecting pipework,
expansion tank, re dousing system, controls systemsand possibly an integrated ossil uel system.
From an operational perspective, one o the most
notable dierences between a biomass heating
system and a conventional ossil uel heating system isthat the biomass boiler is best suited to being operated
relatively continuously (between c.30% and 100% o
its rated output). This means that a heat store, and/or
a ossil uel system to manage peak demands, is otenspecied in addition to the biomass boiler. Also, a
biomass heating plant will be considerably larger in
volume than an equivalently rated ossil-uel plant due,in part, to the inherent combustion characteristics o
solid, organic materials.
Biomass uel is typically woodchips or wood pellets,
but it can also be other biomass material such aslogs and straw bales. I t is normally delivered rom a
dedicated uel supplier, but it can be on-site material
(e.g. on arms and estates), or delivered rom a uel
supplier in a less processed orm (e.g. logs, slabwood,roundwood etc.).
Fuel must be physically delivered into a uel storage
system (a small shed-type building or purpose-builtspecialist store) and then must be transerred into the
combustion grate o the main boiler via a mechanical
handling system (e.g. screw auger/ram stoker).
The biomass boiler is the heart o the biomass heating
system, and there are many dierent types and models.
These are usually classied by the type o biomass
they are suitable or use with (e.g. dry woodchip,wet woodchip, pellet, log, bale, etc.); by the type o
combustion grate; and also by their rated thermal
output. They vary rom manually ed, generally small,boilers with ew controls, through to ully automatically
ed boilers with automatic ignition and ull remote
monitoring and control systems. The choice o boiler
type is determined, in the rst instance, by the uelthat is intended to be used, and then the level o
automation required; this is a trade-o between
convenience and cost.
The ancillary equipment (such as the fue/chimney)
and ash handling is mostly determined by the type
and size o the boiler, whilst the need or thermal
stores (e.g. hot water cylinders) and ossil uelstand-by is determined by the site heat load and
reaction times required.
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12 Introduction
The biomass market
When considering the installation o a biomass boiler
or CHP system, it is helpul to appreciate the currentposition o the biomass market. This section provides
some statistics on the contributions o biomass to
global energy supplies and observations about thecurrent state o the UK biomass energy supply industry.
Contributions o biomass to energy supplies
Worldwide in 2006, o the 12.7% o primary energythat was supplied by renewables, almost 75% (9.5% o
total) came rom solid biomass13 (around 1,100 Mtoe14).
This is due to the widespread use o solid biomass or
domestic purposes in developing countries. However,while contributing more than any other orm o
renewable energy, solid biomass is also growing
more slowly than other orms. For example, whilewind energy grew at an average rate o 24.5%/year
between 1990 and 2006, solid biomass increased
at only 1.5%/year. This is perhaps due to developednations giving solid biomass relatively little priority
as a commercial energy technology, and growth
in developing countries increasing only due to
population growth.Looking at Europe, the extent to which heat is derived
rom biomass sources varies signicantly between
countries. Figure 3 shows that at most (Sweden), heatrom biomass sources provide approximately 38%
(~60 TWh/year) o the countrys overall heat demand.
For comparison, the UK currently uses about 0.7 Mtoe o
biomass to supply heat15, this is equivalent to less than
0.6%16 (~4 TWh/year) o the UKs overall heat demand.
There is signicant potential or a greater proportion o
the UKs heat to be derived rom biomass. For example,it is estimated that a contribution o 6% (a more
than tenold increase) is achievable i just industrial,
commercial and residential heat customers thatare located o the gas grid switched to biomass17.
Moreover, there is a strong requirement to move to
biomass and other low carbon heating uels to mitigate
climate change. Currently around hal (49%) o the UKstotal primary energy demand is in the orm o heat and
meeting this demand with ossil uels causes about
hal (47%) o the countrys total carbon emissions.
With the introduction o new targets across the EU or
the total primary energy to be supplied by renewables,
as agreed by EU Heads o State in 2008, the questiono how much heat biomass sources could provide
over the next decade is highly topical. Considering the
proposed UK target o 15% total primary energy, the
recent BERR Renewable Energy Strategy consultation18suggests that 14% o the UKs total heat demand may
need to be derived rom renewables by 2020, with
a little under hal o this (c.6.4%) coming rom solid
biomass. This is roughly equivalent to 39.8 TWh/a(3.4 Mtoe).
State o UK biomass industry
The UK biomass heat industry is currently small,
refecting the relatively small amount o heat and
electricity derived rom biomass. The majority obiomass boilers are manuactured and imported rom
other European countries, with UK companies tending
to ocus on biomass system installation, operation
and maintenance. Approximately 35 rms are activein the installation o commercial scale systems o
greater than 100 kWth capacity, with services rangingrom supplying and commissioning boilers to completeturnkey installations, including design and installation
o district heat networks.
13 Source: International Energy Agency (2006 data).14 Million tonnes o oil equivalent.15 Source: BERR energy statistics. The gure is or 2007 and includes several orms o biomass in addition to solid biomass.16 0.6% is an estimate o the total heat provided rom renewable sources.17 Source: Oce o Climate Change.18 Source: Renewable Energy Strategy Consultation. http://renewableconsultation.berr.gov.uk/
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13Biomass heating: A practical guide or potential users
19 EurObservER Barometer project(2007) www.erec.org/projects/ongoing-projects/eurobserver (note that the gures used in this chart exclude the useo biomass in domestic applications, thus the countries which eature most signicantly in this gure are those having developed the use o districtheating networks).
20 Van Steen, H (2007) European Commission Renewable Energy Policywww.greenpowerconerences.com/renewablesmarkets/documents21 Estimated rom UK Energy in Brie 2008 BERR.
The biomass market (continued)
Considering biomass uel supplies, at least 70%21 o the
UKs biomass by total primary energy is estimated tooriginate rom the UK, while the remainder is imported.
There are estimated to be over 200 UK companies and
organisations directly involved in the supply o biomassuels. Current suppliers o solid biomass uels range
rom small companies or individuals who may also
operate other businesses in addition to uel supply,
through to large scale, orestry contractors supplyinglarge quantities in bulk. Recently, a number o biomass
uel supply cooperatives/brokers have emerged who
provide a single contracting party but draw upon uelsourced rom a number o suppliers.
Figure 2Gross solid biomass heat production rom thermal and CHP plant in EU countries, 200519
2.5
2
1
1.5
0.5
0
Sweden
France
Finland
Denmark
Austria
Germany
Belgium
CzechRepublic
Poland
Slovakia
Netherlands
Hungary
Slovenia
Heat(MTOE)
Country
CHP plants
Thermal heat plant only
Figure 3Shares o biomass in the national heating markets o EU countries, 200620
40
30
20
10
0
Sweden
Finland
Lithuania
Latvia
Estonia
Portugal
Austria
Slovenia
Denmark
France
Greece
Spain
Italy
Poland
Germany
Hungary
Ireland
Czech
Republic
Belgium
Slovakia
UK
Ne
therlands
Lux
embourg
Cyprus
Malta
Biomassshare(%)
Country
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Part 2 Technical manual
This part o the guide is a reerence manual containing key background
inormation on the main elements o a biomass heating solution:
uel (characteristics, sourcing, reception, storage), and plant (design,
eatures, operation).
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2.1 Biomass uels
This is an introduction to the range o types, physicalcharacteristics, standards, and the delivery/storage
methods o biomass uels suitable or heating systems.
2.1.1 Sources o uels
There is a wide range o original sources o biomass uels
which can be broadly dened in terms o wet and dry
sources. Under these two broad headings, the sourcescan be grouped into ve categories:
1. Virgin wood
Dry includes roundwood,
harvesting residues (brash), bark,sawdust, crowns, and residues o
tree surgery.
2. Energy crops
Dry includes woody energy crops(short rotation orestry, willow,
eucalyptus, poplar), grassy energy
crops (miscanthus and hemp); sugarcrops (sugar beet); starch crops
(wheat, barley, maize/corn); oil crops(rape, linseed, sunfower); and even
hydroponics (lake weed, kelp, algae).
3. Agricultural residues
Wet includes pig and cattle slurry,sheep manure, grass silage.
Dry includes poultry litter, wheat
or barley straw, corn stover.
4. Food residues
Wet includes wastes rom various
processes in the distillery, dairy,
meat, sh, oils, ruit and vegetables
sectors.
5. Industrial residues
Wet includes sewage sludge.
Dry includes residues rom
sawmills, construction, urnituremanuacturing, chipboard
industries, pallets.
Not all these sources, are suitable or use in the types
o biomass heating plant considered in this guide.
This guide concerns itsel with dry biomass uels only.
The typical sources o uel or such biomass plant are:virgin wood, woody and grassy energy crops, certain
agricultural residues, products such as wheat or barleystraw and in some circumstances pressed oil cakes22
and certain industrial wood residues.
Virgin wood
Virgin wood is untreated and ree o chemicals and
nishes. It comes rom a variety o sources; orestry is the
primary source, with other sources being arboriculturalarisings (tree surgery waste) and co-products rom wood
processing acilities (such as sawmills, urniture actories).
Typically, high quality logs and stemwood enter the
wood processing industry, leaving less valuable timberavailable or processing into wooduel. This generally
includes branches, bark and brash23. The provenance
o the virgin wood is o critical importance as this canaect both plant perormance and any environmental
permits that may be required (see section 3.2.5) .
22 Some existing users o heating-oil red plants have investigated using biodiesel in place o heating oil in conventional plant. However, it should benoted that using biodiesel in this manner may not oer signicant cost benets over heating oil and will have the associated sustainability/carbonsaving uncertainties that using biodiesel as a vehicle uel has.
23 It should be noted that high levels o dirt (rom stumps) can cause perormance issues with boilers and wood rom seaside and roadside areas cancontain high levels o salts which can also aect plant perormance/service lie.
Courtesy o Econergy
Courtesy o B&V
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Fuel supply and sustainability
Like conventional heating systems, biomass systems
are reliant on physically produced and traded uelsupplies. The availability and costs o these supplies
vary over time, subject to the demand or uels or
energy production but also due to wider market actors,(or example, the case to grow dedicated energy
crops depends on conditions in the arming industry).
Yet it is possible to estimate the total quantity o
biomass available or heating systems in the UK,as outlined below.
The production o organic material or energy purposes
(heat, electricity and transport) can have environmentaland socio-economic impacts, some o which are
negative. Over the past year, media attention has been
drawn to these impacts and cases made or improved
sustainability standards and changes in Governmentpolicy27. Fortunately, the types o biomass uel used or
UK heating systems are unlikely to raise sustainability
concerns, as this box explains.
UK uel supplies
It is currently estimated that 3.11 MToe (36.2 TWh) o
biomass is being used annually to generate electricity,and 0.45 MToe (5.2 TWh) to produce heat28. Studies
o UK biomass resources suggest this usage is about
hal the total quantity o biomass currently available.The 2005 Biomass Task Force29 estimated this as 4.8-5.7
Mtoe (55.8-66.3 TWh), and 5.6-6.7 Mtoe (65.1-77.9 TWh)
was suggested by a more recent study30.
Current resources represent only a raction o what
could be available in uture. In a scenario in which
quantities o biomass rom orestry and waste
resources stay the same as today, but increasing
amounts o energy crops are produced, 8.3 Mtoe(96.5 TWh) has been orecast or 202031. This is
equivalent to almost one hundred and orty thousand400 kWth boilers (operating at a 20% capacity actor).
This suggests that or the oreseeable uture, sucient
UK biomass uel resources could exist to supply a largenumber o new biomass heating systems thereore
in theory, any new installation should not have diculty
in securing supplies.
From the perspective o site owners, biomass uels
can be purchased rom an increasingly wide rangeo suppliers. However, since biomass heating is still
currently an early-stage market, extensive uel supply
chains have yet to be ully developed. As consequences
o this:
Fuels tend to vary in their specications and quality,and obtaining biomass o a required or desired
standard can sometimes be challenging. Forurther details, see the box on uel standards and
specications on page 23.
Sourcing uels may be dicult in certain areaso the UK. However, new networks o suppliers arebeginning to take shape with support rom bodies
such as regional development agencies. A list o
such supplier networks is available on the Carbon
Trust website (www.carbontrust.co.uk/biomass).
Sustainability
When considering biomass and issues o sustainability,
it is important to understand that:
The types o solid biomass likely to be used or UKheating systems (e.g. wood chips or pellets) arebased on eedstocks di erent to those used or thecurrent generation o liquid biouels (e.g. palm oil)
or transport.
This distinction is highly signicant to the carboncases or such types o biomass and other aspects
o their sustainability, with solid biomass oeringmany advantages over current transport biouels.
For example, whereas growing palm oil in a developing
country may involve land degradation or large-scaledeorestation (both o which could increase carbon
emissions), using compressed sawdust or residue
materials such as orestry brash in the UK to make
wood chips and pellets requires no such compromises.Such materials (residues, sawdust, brash) are:
Unlikely to have been grown on prime agriculturalland, so are not in competition with ood crops.
Likely to have been harvested as part o a sustainableland management process. For instance, the majority
o UK orestry activities are subject to Forestry
Commission sustainable management regulation.
27 UK Government perspectives are given in the House o Commons Environmental Audit Committee report Are Biouels Sustainable(2008),and the Department or Transport report Review o the Indirect Eects o Biouels.
28 Dera UK Biomass Strategy (2007).
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2.1.2 Types o uel
The majority o raw biomass materials (eedstocks)
require some orm o processing beore they becomebiomass uels. Processes can range rom simple cutting
and drying to more involved processes like pelletising.
The method o processing which a biomass eedstockundergoes is important because it will determine its
eventual application and useulness as a uel and will
also determine the type o biomass heating plant that
can be used or a project.
29 Dera (2005) Biomass Task Force Report to Government.30 Dera (2007) UK Biomass Strategy(2007).31 Dera (2007) UK Biomass Strategy(2007).32 For details o other relevant standards, see the box on page 23.
Fuel ormat Utilisation
Logs Most commonly used in small-scale systems (
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Characteristics
Biomass uels have a range o characteristics which
aect their perormance and also the type o biomass
heating equipment they can be used in. Some o themost important actors are listed below and a table
presenting the most common uels and their associated
characteristics is given at the end o this section.
Caloric Value (CV)
This is a very important characteristic; i t indicates the
heating potential o a uel and is a measure o its energycontent. It is dened as the amount o heat released
rom a specic unit o uel by its complete combustion.
Biomass uel CVs are conventionally expressed as MJ/kg.The caloric value o a uel is expressed either as Gross
Caloric Value (GCV also sometimes known as Higher
Heating Value (HHV)), or Net Caloric Value (NCV also
sometimes known as Lower Heating Value (LHV)).
Net Caloric Value (NCV) is the quantity o heat giveno by the complete combustion o a unit o uel when
the water vapour produced remains as a vapour andthe heat o vaporisation is not recovered. This can be
calculated by subtracting the heat o vaporisation o
the water produced rom the GCV. The NCV is more
widely used in the UK than the GCV.
Gross Caloric Value (GCV) is the quantity o heatliberated by the complete combustion o a unit o uel
when the water vapour produced is condensed, andthe heat o vaporisation is recovered. The water is
condensed by bringing the products o combustion
(fue gases) below 100C (as in a condensing plant).This generally does not apply or biomass as the fue
gases cannot be cooled below c.130C, and hence the
water vapour cannot be condensed.
Note that (or wood) the GCV is usually 6-7% higher
than the NCV.
The key determinant o biomass materials caloric value
is the inherent moisture content (MC). The MC o materialcan vary greatly rom c.5-8% or wood pellets, c.35% or
conditioned uel and up to 65% or reshly elled timber.
The greater the MC the less energy is contained withinthe uel.
Moisture content (MC)
This is expressed as a percentage, measured eitheron a wet or dry basis. Wood suppliers (or example)
typically use the wet-basis method because it givesa clearer indication o the water content in timber.
The wet basis calculation expresses the moisture content
as a percentage o the mass o the material including
any moisture. In the ormula below oven dry mass isdened as the mass o biomass which has had all themoisture driven out:
Wet basis
MC = Fresh mass Oven dry mass x 100 (%)Fresh mass
The dry basis calculation expresses the moisture
content as a percentage o the oven dry mass:
Dry basis
MC =Fresh mass Oven dry mass
x 100 (%)
Oven dry mass
A higher MC implies a lower caloric value as each unit
mass o uel contains less oven dry biomass which is
the part o the uel that actually undergoes combustionto release heat. The eect is more noticeable or most
biomass heating systems where the water vapour in
the combustion products cannot be condensed. This is
because the moisture in the uel also has to be vaporisedbeore combustion can occur and this requires energy
input that cannot be recovered later.
The majority o the biomass industry uses wet basiswhen discussing biomass uels.
Figure 4 shows the caloric value o wood (measured in
MJ/kg) as a unction o its moisture content (MC). Clearly,dry wood has greater energy content than wet wood, and
this is refected in the typical market price or wooduels.
The ormula or calculating the eect o uel moisture
content on net caloric value is outlined in Appendix B.
Figure 4The eect o moisture content (MC) on
caloric value (NCV)
20
0
5
10
15
0 25 50 75Netcalorificvalueoffuel(M
J/kg)
Moisture content (%)
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Bulk density
This is a measure o the mass o many particles o the
material divided by the volume they occupy; the volumeincludes the space between particles. The higher the bulkdensity, the more mass o uel exists in a given volume.
For example wood pellets (c.660kg/m3) have a higher
bulk density than wood chips (c.250kg/m3). Bulk density,unlike density, is not intrinsic to a material; or example,
the same piece o wood could have dierent bulk
densities i processed into logs, pellets or woodchips.
Moisture content also aects bulk density as each particlehas a greater mass but does not occupy more space.
This is an important point because uels with higher
moisture contents will have greater masses and,thereore, have lower bulk densities. With higher moisture
content comes lower energy density, and thereore the
volume o uel required or a given amount o heat will
be larger.
Energy density
Energy density is derived rom the bulk density o a uel
and is a measure o the energy contained within a unito uel. Energy density is conventionally expressed inMJ/m3.
It can be derived by multiplying caloric value (MJ/kg)
by bulk density (kg/m3).
Energy density is an important variable that will help
users understand volumetric uel consumption rates,
the size o uel storage required, the number o deliveries
required and the total annual quantity o uel required.
Table 3Typical bulk, caloric and energy densities o dierent biomass and ossil uels
Energy density = CV x Bulk density
(MJ/m3) (MJ/kg) (kg/m3)
Source: Gastec at CRE Ltd. and Annex A, Digest o UK Energy Statistics 2007
Fuel
Net
CV1
MJ/kg
CV
kWh/
kg
Bulk density
kg/m3
Energy density
by volume
MJ/m3
Energy density
by volume
kWh/m3
Lower Upper Lower Upper Lower Upper
Woodchips @ 30% 12.5 3.5 200 250 2,500 3,125 694 868
Log wood (stacked
air dried: 20%MC)
14.6 4.1 350 500 5,110 7,300 1,419 2,028
Wood solid oven dried 18.6 5.2 400 600 7,440 11,160 2,067 3,100
Wood pellets 17 4.7 600 700 10,200 11,900 2,833 3,306
Miscanthus(bale 25%MC)
12.1 3.4 140 180 1,694 2,178 471 605
House coal 29 8.1 850 24,650 6,847
Anthracite 32.1 8.9 1,100 35,310 9,808
Oil 41.5 11.5 865 35,898 9,972
Natural gas - - - 36 10.13
LPG 46.9 13.0 500 23,472 6,520
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Particle size/dimensions
Biomass heating systems require physical handling
mechanisms or transerring uel rom where it is storedto where it is combusted (in the plant). Fuel particlesthat are too large can jam certain uel eed systems
(e.g. augers) and, thereore, particle size is an important
characteristic o a biomass uel. All biomass uels cancome in a wide variety o shapes and sizes. Aside rom
moisture content, the particle size is the other key issue
to consider when matching system design with the uel
available (see box on page 23 or urther details on uelspecications and classes).
Certain uel eed systems can handle uels with a broader
range o particle sizes (e.g. walking foors and ramstokers). Others (e.g. those designed to use pellet uels)
can only tolerate a more narrow range o particle sizes.
Mechanical durability
I the system being specied can only use pellet uels,
then the mechanical durability (how well the pellets stay
together during handling) is a key consideration andshould be specied. One issue that can occur with pellet
uels is disintegration (during the handling process).
Good quality pellets should have a mechanical durability
o at least 97.5%, meaning less than 2.5% o the pelletswill be broken down ater delivery. Many pellet uels need
some orm o additive to act as a binding agent, which
should be known and specied by the manuacturer.
Very small particles in the uel (such as sawdust) may
represent a certain proportion o the total weight o
a sample o biomass uel. Excessive amounts o such
material may cause problems such as compaction inaugers and smothering o the re bed.
Original source
This characteristic is important as it has a bearing on
whether or not the uel is classed as a waste, and thuswhether a project will need specic permits. The original
source and knowledge o the supplier may also indicatethat certain physical and chemical contaminants may
be present in the uel. For example, stones, gravel and
dirt (which can aect plant perormance through theormation o clinker in the combustion chamber, and
through jamming augers) can become caught up in
uel i it has been sourced rom tree surgery materials
originally. Also, material rom tree surgery can sometimesincorporate leaves and other green material (which are
not suitable or combustion in most biomass heating
systems). I it is known and accepted that the uel may
contain residual materials such as solvents, chemical
treatments and the others listed above, then the plant
must be specically designed to deal with these.
The source should be clearly identied when procuringuel to guide environmental consent practice and
plant specication.
Ash content
Although the amount o ash produced is partly dependent
on the type and perormance o the biomass plant it is
being used in, it is also an inherent uel property which isspecied as a uel characteristic. For example, a woodchip
or pellet uel would be expected to have an ash content
o around 1% by weight (1-3% by volume) o the uelconsumed, whilst miscanthus (a type o energy crop)and straw will be higher.
Chemical content
It is natural or biomass to contain low levels o mineral
salts and other trace non biomass material, taken up
rom the soil or air during growth. The presence o these
salts and other elements in virgin biomass uels doesnot normally cause any signicant issues, but it does
partly determine the level o gaseous/particulate
emissions, ash, and slagging (also known as clinkering).I, or instance, an annual crop is being used (e.g. straw)
then more care is required, as these can have higher
levels o alkaline metal salts.
For more detail on the specic properties o a wide rangeo biomass eedstocks used or uels, the Phyllis database
(www.ecn.nl/phyllis) contains inormation on a wide
range o dierent chemical and physical characteristics.
Note that uel characteristics such as the original
source, ash content, chemical content and, to
an extent, moisture content will have an eecton the level and composition o certain emissions
to the air rom the biomass heating plant that they
are ultimately used in. This should be borne inmind when choosing uel i local air quality is to
be a key consideration as part o the necessary
planning/consenting/permitting process required
or the project in question (see section 3.2.5 orurther detail).
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23Biomass heating: A practical guide or potential users
Fuel standards and specications
Successul operation o a biomass heating system
is strongly dependent on the use o properlyspecied uel.
To aid the matching o heating systems with uel
supplies, uel standards have been introduced inseveral European countries. One o the best known sets
o standards are the norm standards rom Austria,
which speciy size, moisture content and various other
important properties o solid biomass uels33. These
standards are being used by some UK uel suppliers
in the absence o equivalent UK standards.
The CEN (European Committee or Standardisation)is developing a common methodology or speciying
the key characteristics (those mentioned above plus
original source, caloric value, chemical composition,physical properties etc.) o all orms o solid biomass
sold within the EU, and also methods or testing these
properties. The CEN specications will eventually be
transposed into member states standards systems(e.g. those o the British Standards Institute).
At the time o writing, the specications are available
only in drat orm, yet they are suciently welldeveloped to be suitable or reerence in uel supply
contracts, and the nal versions are likely to be very
similar. They can currently be downloaded ree o
charge rom the Biomass Energy Centre website34.
Regardless o which set o standards are reerred to,
it is important that the site owner works closely with
both the uel supplier and system installer to ensurethat the uel purchased is suitable or the system,
that the uel supplier undertakes to deliver a consistent
quality o uel and that the uel can be stored andhandled at the site in the correct manner. Drat
uel supply contracts to acilitate such cooperation
can be downloaded rom the Carbon Trust website(www.carbontrust.co.uk/biomass).
33 http://www.sew.co.uk/links/SEWF_Chip_Spec.pd34 http://www.biomassenergycentre.org.uk/pls/portal/BIOAPPS.BSI_REGISTRATION_FRM.show
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2.1.3 Fuel delivery, storage, extraction and eed
This section deals with the delivery and storage o
biomass uel or heating systems as well as how it can
be extracted rom the store into the combustion unit.
A well-designed system or delivering, storing and
transerring solid biomass uel is essential to ensure
a smooth-running biomass heating system.
The solution must be t or purpose and suitable or
the lie o the installation (typically up to 20 years).
Specic site circumstances may mean that a degree o
compromise to the ideal solution is necessary. However,time spent planning and consulting with parties involved
in the design, installation and operation (plant installer,
uel supplier, engineering contractors, architects etc.) atan early stage will help to ensure that common problems
are avoided.
A good uel delivery, storage and extraction solutionwill typically:
3Allow delivery by standard vehicles thus allowing uel
supply rom a range o dierent parties.
3 Enable speedy and simple discharge o uel without
the need or large amounts o attendance by sta.
3 Prevent the ingress o water but also allow moisture
vapour to escape rom stored uel.3Allow sae dust venting and management where
required.
3Meet necessary building regulations and health andsaety requirements.
3Keep costs to a minimum35.
Fuel delivery
There are a number o dierent uel delivery and
reception options available. Ultimately, the nature o the
system adopted will be dependent upon:
The proposed uel or the application (wood pellet,chip, logs, bales etc.).
The area available and any other physical accessconstraints at the site.
The area required or the delivery vehicle to accessthe uel store.
The proposed delivery vehicles available romprospective uel suppliers.
The typical methods and vehicles used in supplyingbiomass uel or heating systems are outlined in Table 4
opposite. The major advantages and disadvantages oeach option are shown in Table 5 (overlea).
35 In most biomass heating projects, the uel delivery, storage, and extraction solution will be a major component o the overall cost. Careul design andalso, where possible, designing to minimal requirements can help to control this cost.
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Table 4Type o uel delivery method/vehicle and typical payloads
Images courtesy o: Wood Energy, Econergy, BSRIA, Highland Wood Energy, B&V
Delivery method Example Typical uel type Typical payload Availability
Flexible hose rom
a blower tanker
Most commonly
pellet but also chip
Pellet: c.15-20m3
(10-14 tonnes)
Chip: c.10-20m3(4.5-6 tonnes)
Pellet common
delivery vehicle.
Chip specialistdelivery vehicle,
not common.
Bulk bag deliveries Pellet or chip 1-2m3/bag Common in
some areas (e.g.Scotland).
Tipper trailer Pellet or chip Chip: c.20-30m3
(6-9 tonnes)
Pellet: c.20-30m3(14-21 tonnes)
Tipper trucks
widely available
and commondelivery method,
particularly or chip.
Scissor lit tippingtrailer
Pellet or chip Chip: 20m3-30m3(6-9 tonnes)
Specialist deliveryvehicle required.
Blower trough and
tipper truck
Chip c.20m3 (6 tonnes) Tipper trucks
widely availablebut blower troughs
are specically
purchased orsite uelling.
Hook lit bin/Ro-Ro
bins
Chip 30m3-35m3
(9-12 tonnes)
Specialist delivery
vehicle required.
Front loader Chip and bales c.1m3 (0.3 tonnes) Commonmachinery or arm/
estate application.
Walking foor
trailer
Chip 60m3 (18 tonnes) Specialist delivery
vehicle required suited to large
scale deliveries.
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Delivery system Benets Drawbacks
Flexible hose rom
a blower tanker High volume discharge possible
(up to 15-20m3 max payload).
Pellets may be deliveredthrough a hose over a length o
c.30m, thus beneting sites with
restricted access.
Metering o delivery is possible.
Specialist vehicles are required (though theseare relatively common amongst pellet suppliers).
Time taken or discharge will be approximately30-45 minutes or a ull discharge o 20m3.
Longer blower runs may result in high levels onoise during discharge.
I uel store is not designed or this method odelivery, wood pellets can become damaged and
disintegrate upon delivery causing excess dust.
Bulk bagdeliveries
Low-cost solution. Fuel type fexibility (suitable or
wood chip or pellets).
Suitable or smaller uelconsumption volumes.
Lorries with built-in cranes aregenerally widely available.
Low delivery volumes (1-2m3 per bag) andthereore deliveries may require multiple bags,
especially i using wood chip.
Fuel may be exposed to moisture i not coveredduring delivery.
More expensive due to the small load dischargeper delivery.
Tipper trailer High speed o delivery.
Tipping trailers/lorries aregenerally widely available,
thereore oering the potentialor uel supplier fexibility/
switching.
High volumes and dischargerates possible, which can
reduce cost.
Requires good vehicle access and clearance toallow tipper bed to be raised.
Requires large storage area to allow ull trailer
discharge (e.g. 20-30m3
). Requires underground/semi-underground store
or vehicle ramp to allow uel delivery.
Partial discharges are dicult to achieve.
Space may be required on-site or vehicle to turn.
Delivery by tipping may cause uel in the storeto be unevenly distributed (manual raking maybe necessary to rectiy this).
Scissor lit tipping
trailer High volume discharge possible.
Can deliver uel to above-grounduel stores (less costly than
subterranean/semi-subterranean
counterparts).
Limited potential to change uel supplier asrequires a more specialist delivery vehicle.
Partial discharges are dicult to achieve.
Delivery by scissor lit tipping may cause uelin the store to be unevenly distributed (manual
raking may be necessary to rectiy this).
Blower troughand tipper truck
Flexible delivery solutionin space-constrained sites
(particularly retrot sites wherestandard uel delivery methods
may not be possible).
Requires careul discharge o material into theblower trough.
Discharge rate limited to c.25m3/hour.
Noisy delivery method (may cause disturbancein built-up areas).
Maximum blower distance is c.2.5m romthe trough.
Table 5Pros and cons o dierent uel delivery methods
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27Biomass heating: A practical guide or potential users
Fuel storage
Fuel storage acilities normally account or a signicantproportion o the overall capital cost o biomass heating
projects and careul consideration needs to be given to
their design and unctionality.
The most appropriate type o uel store is usuallysite-specic, and the decision should be based on a
reconciliation o the ollowing actors:
The fexibility/availability o the delivery method romthe uel supplier(s).
Available space at the site and any site-specicphysical access constraints.
The location o the existing or proposed plant roomin relation to the uel store.
Appearance/aesthetic requirements. Fuel type to be used, which will aect uel store
volume.
Site topography and geology (i.e. ground conditionsi a subterranean store is being used).
Costs o dierent congurations.
Liaison between prospective suppliers and the project
design team is essential to deliver a cost-eective
solution or uel reception and storage.
Fuel stores can be categorised into our main types,
(with variations on each present in the UK).
1. Below-ground/partially below-ground
(subterranean) stores.
2. Above-ground stores.
3. Integrated stores within existing buildings.
4. Removable containerised storage.
Logs and bales are normally delivered using less automated processes such as a sel-loading lorry with a crane (larger sizes) or via net bags(smaller sizes). Fork-lit trucks also used to deliver bales and move them around sites.
Delivery system Benets Drawbacks
Hook lit bin/
Ro-Ro bins Minimal civil works required
(concrete pad only).
Oers an integrated uel storageand delivery solution (cassette-
style containers o uel replaced
as necessary by uel supplier).
High volume o uel in onedelivery (c. 35m3).
Requires specialist uel supplier or Energyservices company (ESCo.) operator.
Ties up capital in the containers or supplier.
Above ground solution may not be suitable orall sites and aesthetics.
Front loader Simple solution.
Widely available.
Can deliver uel to out-o-reachlocations (above ground stores).
Low delivery volumes.
Slow speed o delivery.
Walking foortrailer
High volume discharge possible.
Widely available. Requires signicant amounts o space or
delivery and turning.
Photocou
rtesyoAsgardBiomass
Biomass boiler unit with automatic ash removal bin and
uel eed auger
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28 Technical manual
Wood log uels may be stored outside; however, they
should be covered to ensure uel remains dry/conditioned.
Bales may be stored in a simple, covered but ventilatedenvironment (e.g. barn).
Key considerations in the design and construction o
uel stores are:
1. Preventing the ingress o water but also having
sucient ventilation to allow the escape o any
condensation given o by the uel residing there.
2. Having sucient strength to be able to tolerate
the outward pressure exerted by a ull load o uel(and any inward orces imposed by surrounding
earth i using a subterranean store).3. Having a simple method o inspecting the level
o uel (e.g. hatch, window, webcam).
4. Keeping the interior ree rom electrical sockets,
switches, and exposed electrical ttings.
5. Meeting the relevant building regulations where
they apply (approved document J Combustionappliances and uel storage systems36 provides
guidance).
6. Minimising uel auger distances rom the plant.
7. Ensuring saety during deliveries (e.g. including a
stop bar) i uel delivery method requires a vehicleto reverse up to the store (can avoid the need or
additional sta to oversee deliveries).
8. Having appropriate security measures in place (i
it is in a place that will be accessible to the public)to prevent illegal access.
9. Allowing or complete discharge rom the supply
vehicle particularly i tipping.
The dierent physical properties o the two main sourceso biomass uel or heating (pellets and chips) necessitate
specic considerations:
Pellets:
I blower delivery is used, the storage unit will needthe appropriate couplings to allow connection to the
pellet blower hose (e.g. a camlock), and the end othis will need to be within the reach o the blower-
truck driver. Also, in this situation a fexible rubber/plastic sheet hanging opposite the inlet pipe is
advisable to avoid pellet damage during delivery.
The storage unit will need an exit port to allow therelease o air when deliveries take place (which can
be tted with a lter to reduce excessive dust exiting
the storage silo).
The point o entry or pellets must be high upenough to enable even lling.
I there need to be bends in the delivery pipework,tapered bends may be preerable, as a 90 angle
could cause damage to pellets during delivery. The foors o the storage unit will need a slope o
at least 40 going towards the eed mechanism
(e.g. auger) to ensure pellets can fow into it.
Any delivery pipe on the storage unit may needto be made rom metal and should be earthed to
prevent static build-up on plastic piping.
36 http://www.planningportal.gov.uk/england/proessionals/en/4000000000503.html
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30 Technical manual
Fuel type Storage location
Below ground
Use or sites with an elevation dierence, where land is at a premium or aestheticconsiderations demand.
Above ground
Lower cost than below ground, with easier access or maintenance. Widest range
o uel store types.
Building integrated
Can be above or below ground. Stores can be simple and cost-eective, i minimal modicationsto existing internal structures are required.
Below ground
See considerations above or pellets. Need to consider that the uel supply vehicle has adequate
manoeuvring space.
Above ground
Same cost advantage as or pellets, but reduces uel delivery vehicle fexibility.
Building integrated
Can be above or below ground. I minimal modications to existing internal structures are
required, these can be simple and cost-e ective, but will be governed by uel supply vehicleand the method o discharge.
Table 6Storing pellets and chips
Woodchips
Woodpellets
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31Biomass heating: A practical guide or potential users
Type o uel store
Purpose-built pre-abricated bunker
Typically lled pneumatically rom blower tanker. Fuel extraction via straight auger orvacuum tube.
Constructed bunker
Possible orms are adapted grain silos, modied storage bunkers, existing cellars with wood
panelling and basic concrete/brick covered spaces. Fuel extraction requires tapered foor tounnel pellets to a central auger. Typical uel extraction via straight auger.
Bag silo
Flexible bag which sits in a support rame. Simple and cost-eective, avoiding need or civil/
construction works. But needs to be positioned in sheltered area or building, not exposed
to rain. Typically lled pneumatically rom blower tanker. Fuel extraction by straight auger
or vacuum tube.Integrated storage hopper
Most suitable or small systems where hopper is attached directly to plant. Usually lled
manually using pellet bags. Fuel extraction by auger direct to plant.
Purpose-built pre-abricated or bespoke storage hopper
Preabricated steel structure or re-enorced plastic hopper. Usually available rom plant
manuacturer/supplier. Typically lled pneumatically rom blower tanker. Fuel extraction
via gravity: tapered foor to central auger.
Storage container
A shipping container, or example. Filled via blower unit or bagged or removable system to
allow o-site relling. Depending on the route rom uel store to plant unit, extraction can bevia straight auger, vacuum tube or gravity ed (inclined foor with auger running along base).
Bespoke internal structure
Can be constructed rom wide variety o materials, e.g. brickwork or main structure withwood panelled interior, or concrete. Filled by tipper trailer, pneumatically rom blower tanker
or ront loader. Fuel extraction typically via straight auger.
Purpose built external structure
Shed-type or lean-to external constructions can be built rom wide variety o materials;
highly fexible.
Constructed bunker
Can be constructed rom wide variety o materials, e.g. blockwork or main structure with
wood panelled interior, or concrete. Typically lled by tipper trailer. Fuel extraction typically
via walking foor or circular sweep-arm agitator.
Bespoke construction
Can be constructed rom wide variety o materials: blockwork with cladding, brickwork with
cladding or steel structures (either purpose built or o-the-shel designs such as ISO container
above). Highly fexible options available.
Bespoke internal structure
Typically suitable or retrot site, with installation within existing building. Can be
constructed rom wide variety o materials, e.g. brickwork or main structure with woodpanelled interior, or concrete. Filled by tipper trailer, pneumatically rom blower tanker or
rom bags (automatically or manually lited). Fuel extraction typically via straight auger.
Images courtesy o: Black & Veatch Ltd., Glyn Edwards, Imperative Energy Ltd., Wood Energy Ltd., Marches Wood Energy
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32 Technical manual
FuelEx
tractionandFeed
FuelEx
tractionandFeedistheprocessoremovinguelromthestoreand
transerringittothecombustiong
rate
othem
aincombustionunit.Anumberomethodsarealreadyinuseinthe
UK,asshowninTable7.
Table7
Fuelextractionsystems
Extractiontype
Picture
Commentary
Fueltype
Typicalscaleo
f
applicability
Batch
ed
Onlyappropriateorbatch-redplants.
Requirescontinuedmanualintervention(daily).
Logs
10kWth+
Baleso
straw
30kWth+
Auge
rs(screw
eed)
Theprimarymeansomovingwoodchipand
woodpelletmaterialromtheuelstoretothe
plantunit.
Blockagesattranserpointsbetweenaugerscan
ariseithemanuacturersuelspecicationisnot
adheredto.
Lengthoaugershouldbeminimisedtoreduce
riskoblockages.
Chip
30kWth+
Pellet
10kWth+
Gravityed
Theuseogravity-edsyste
msisonly
appropriateorpelletplants.
Woodpelletsareeitheraugu
redalongthelengtho
ataperedfoor,orunnelled
toacentralpointviaa
baggedstore,etc.Fromheregravitydropsittothe
plantunitorasecondaryau
ger/pneumaticeed.
Pellet
10kWth+
Pneumatic/
vacuumeed
Thesesystemsrequirecare
uldesign,
considerationobends,length,sizeovacuum
tubes,andblowingpressur
es.Thissystemis
usuallylimitedtoapplicatio
nssmallerthan
50kWthandisonlyapplicab
letopelletsystems.
Pellet
10kW-50kWth
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33Biomass heating: A practical guide or potential users
Imagescourtesyo:PeterTeisen/Farm2000Ltd.,EconergyLtd,BSRIALtd.,Black&VeatchLtd.,Imp
erativeEnergyLtd.
Extractiontype
Picture
Commentary
Fueltype
Typicalscaleo
f
applicability
Agita
torarms
withauger
Agitatorarmswithanaugerrunarethemost
cost-eectivemeansoueltranseratthe
mediumscale,andconsequ
entlytheyarethe
mostwidelyused.
Essentiallythespringarms
agitatetheuel,
makingsureiteedsintoacentralauger,which
inturneedstheplant.
Theyareinstalledatanang
leand,thereore,
therewillbesomedeadspaceundertheagitator
discandarms(unlessaals
efoorisinstalled).
Thisareawillneedtobeaccountedorwhen
assessingavailableuelsto
ragevolume.
Agitatorarmlengthsmayn
eedtobedesigned
toavoiddamagetowallsan
darms.
Chip
30kWth+
Pellet
30kWth+
Walkingfoor
Walkingfoorsshufetheu
elalongthelengtho
theuelstoretowardsanau
gerwhicheedsthe
plant.Theuelismovedor
wardviahydraulic
rams/nswhichsituponaconcretepad.
Walkingfoor-basedsystem
scanreceivebulk
deliveryandarethereoresu
itedtolargersystems.
Theconcretepadandthew
allsothestoreneed
tobesucientlystrongtowithstandtheorces
andpressuresexertedbyaullloadouel.
Chip
1MWth+
Pellet
Generallynotusedor
pellets,althoughtechnically
theyarecompatible.
Conv
eyor
Conveyor(belt,chainorhydraulicreciprocating)
ormechanicalgrabsystemsaregenerally
concentratedatthelargesc
aleowooduel
installations,wherethereis
asignicant
throughputomaterial,orw
heretheuelisoa
largeparticlesizethatpreventstheuseoaugers.
Chip
11MWth+
Pellet
Notapplicablet
opellets
atthisscale.
Grab
Chip
3MWth+
Pellet
Notapplicablet
opellets
atthisscale.
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34 Technical manual
Fuel cost actors that infuence uel cost
All eedstocks require some orm o intermediate
processing to convert them into a biomass uel suitable
or use in a heating system this can be as simple as
drying in the case o wood logs or more involved suchas pelletisation. The major actors which will have an
infuence on price are outlined in Table 8.
Detailed uel costs
For the majority o heating applications, in the scale
range under consideration in this guide (0.1-3 MWth),
uel is supplied in the orm o woodchips or woodpellets37. Table 9 provides an indication o the cost o
a variety o processed and unprocessed wooduels.
The cost o dierent orms o biomass uel is highlyvariable across the UK, and Table 9 provides guideline
gures only38.
Containerised solutions
Some suppliers oer containerised systems where
the plant(s), uel storage, handling and all associatedbalance o plant are contained within single,
preabricated units. Systems o this kind up to 450kW
in size have been installed in the UK (with largersystems possible using modular capacity). They
are, essentially plug and play options that oer
several advantages such as minimising disruption
to existing buildings, speed o installations andsimplicity. In the right circumstances, they can be
very cost-eective solutions. Image courtesy o Imperative Energy
Table 8Factors aecting wooduel price
Logistics Quality Market
Distance rom rawmaterial supply.
Delivery vehicle.
Frequency andvolume o delivery.
Discharge rates.
Form o delivereduel e.g. slabwood 50 MWth IPPC Part A1 (Large
Combustion PlantDirective applies)
Environment Agency
Residues or which WIDapplies treated wood
e.g. painted urniture
3 MWth WID applies (IPPC Part A1) Environment Agency
Table 21 Summary o environmental permissions or biomass heating equipment
(IPPC): Integrated Pollution Prevention and Control(LA-IPPC): Local Authority Integrated Pollution Prevention and ControlSource: AEA Energy and Environment
Initial
assessment
Detailed
easibility
Procurement and
implementation
Operation and
maintenance
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61Biomass heating: A practical guide or potential users
3.2.6 Perorm ull economic appraisal
As well as o ering lower carbon emissions, biomass
heating systems can have lower lietime (or net present
value) costs than ossil uel plants. This is due to thecosts o biomass uels being lower than those o several
ossil uels typically used or heating (e.g. heating oil,
LPG, electricity).
However, the capital costs o biomass systems tend to
be higher than or ossil uel boilers. Consequently, in
order to choose biomass systems on nancial grounds,
one needs to take a long-term view towards the overallinvestment, rather than a short-term view o just
upront costs.
This section introduces the main actors aecting costs,both capital and operational, and gives a worked example
or a 400 kWth biomass heating system.
Beore perorming an economic appraisal o theproposed system, it is useul to understand the dierent
components, structure and indicative levels o biomass
heating systems costs, both capital and operational.
The main reasons why biomass heating systems are
more expensive than equivalent ossil uel systems are:
1. Some o the basic principles o solid uel combustion
mean that the biomass plant unit needs to be largerthan typical ossil uel systems. Also, biomass plants
will generally contain more mechanical components
(such as ans, ash extraction equipment etc.).
2. As solid uel systems, biomass heating plants
need uel storage acilities (and extra space to
accommodate the larger plant unit itsel). Unless anexisting building can be used to perorm this unction,
uel and plant storage is usually a signicant part o
overall system cost.
3. Some orm o uel extraction/eed method will be
required (e.g. a screw auger), which adds to overallsystem cost.
4. At present in the UK, biomass systems are sold insmall numbers (compared to the market or ossil
uel equipment) and are oered by a relatively
small number o providers. Accordingly biomassheating equipment does not benet rom the
economies o scale that ossil uel equipment does.
5. The majority o systems installed in the UK are
imported rom continental Europe which can involve
additional importation costs. In addition, variations inthe Sterling-Euro exchange rate at the time o systemprocurement can have an eect on nal costs
(although this could be positive as well as negative).
Capital costs
Figure 17 provides a cost breakdown o the major
elements or a recent real-lie example o a (500 kW th)biomass heating system.
Individual site circumstances will mean that the actual
costs o projects may vary signicantly even or systems
o a similar installed capacity.
The reasons or such variations are largely connected
to the specic circumstances o the site and the owners
requirements or the project:
1. Some sites may be able to make use o existing
buildings or simple on-site structures to act as the
uel storage acilities and/or boiler housing acility.However, certain projects may require very complex
constructions/alterations to enable a biomass heating
system to be deployed.
2. Certain contract structures can have an impact ontotal costs or example i the site owner is able to
carry out any necessary civil, electrical and/or design
works in house this can reduce the overall capitalcost. However, complex contracting structures within
projects (multiple layers o contracting companies)
may increase costs as contingency unding is
actored in to take account o any uncertainties inthe contract.
3. Historically, some projects have been specied
above the minimum unctional levels necessary orcorrect operation. This is usually either or aesthetic
reasons or because the system is to orm part oan exemplar or demonstration scheme to promoterenewable energy.
4. In some cases sites require signicant building
alterations or integration works to enable
retrotting o a ull biomass heating solution.
Figure 18 (over) gives illustrative installed capital costs
o complete biomass heating systems across a number
o size ranges and shows a spread o costs within eachsize range.
Initial
assessment
Detailed
easibility
Procurement and
implementation
Operation and
maintenance
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