SUPPLEMENTARY DATA

Life cycle assessment of conventional and advanced two-stage

energy-from-waste technologies for methane production

C. Tagliaferri1,2, S. Evangelisti1, R. Clift3, P. Lettieri1*

C. Chapman2, Richard Taylor2

1Department of Chemical Engineering, University College London, Torrington Place London WC1E

7JE, UK.

2Advanced Plasma Power (APP), Unit B2, Marston Gate, South Marston Business Park, Swindon,

SN3 4DE, UK.

3Centre for Environmental Strategy, The University of Surrey, Guildford, Surrey, GU2 7XH, UK

*Corresponding author: Email: p.lettieri@ucl.ac.uk; Phone: +44 (0)20 7679 7867

S.1. Life Cycle Assessment Methodology

The Global Warming Potential (GWP) characterises and calculates the impact of greenhouse gases

based on the extent to which these gases enhance radiative forcing. GWP values for specific gases,

developed by the Intergovernmental Panel on Climate Change (IPCC), express the cumulative

radiative forcing over a given time period following emission in terms of the quantity of carbon

dioxide giving the same effect (IPCC, 2006). Following common convention, for example in the

Kyoto Protocol, the 100-year values have been used here. Carbon dioxide from biogenic carbon is

sometimes excluded from the comparison in the GWP (Christensen et al., 2009) because it forms part

of the renewable carbon cycle, theoretically removed from the atmosphere in succeeding products.

However, in this study carbon dioxide emissions from biogenic carbon are included in the estimates

for the Global Warming Potential (GWP) because the assessment is based on existing waste streams

with defined carbon content so that the production of the materials in the waste does not enter the

analysis. Therefore the total carbon content of the waste is considered, with no distinction between

biogenic and non-biogenic carbon.

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The Acidification Potential (AP) quantifies the impact of acid substances and their precursors such as

SO2, NOx and HCl. Rain, fog and snow trap the atmospheric pollutants and lead to environmental

damage such as fish mortality, leaching of toxic metals from soil and rocks, and damage to forests and

to buildings and monuments. Abiotic Depletion (ADP) addresses the problem of the diminishing pool

of resources, focussing on the depletion of non-living resources such as iron ore, crude oil, etc. When

considering fossil energy resources, the measurement unit of abiotic depletion is MJ; whereas when

the depletion of element is quantified, the measurement unit of abiotic depletion is kg of Sb eq. The

Eutrophication Potential (EP) includes all pollutants that promote microbiological growth leading to

oxygen consumption, such as “algal blooms”. Nitrogen and phosphorus are the two main nutrients

implicated in eutrophication: they can cause shifts of species composition and increased biological

productivity. The Ozone Layer Depletion Potential (ODP) quantifies the thinning of the stratospheric

ozone. Chlorinated and bromated substances increase the rate of ozone destruction. Finally, the Fresh

Water Aquatic Ecotoxicity Potential (FAETP) assess the toxic effects of polluting compounds to

water life based on both the inherent toxicity of a compound and the potential human exposure

(Guinée, 2002).

In this study, the so called ‘zero burden approach’ is used (Buttol et al., 2007; Coleman et al., 2003):

the waste life- cycle starts from the moment when the material becomes waste, through the treatment

processes until the material ceases to be waste and becomes an emission into air, soil or water, inert

material in a landfill, or a useful product. Whether or not and how considering the biogenic carbon has

been a much debated subject in literature (Ballinger et al., 2009; Biobased Products Working Group,

2010; Cherubini et al., 2011; CHERUBINI et al., 2011; Christensen et al., 2009; Levasseur et al.,

2013; McDougall et al., 2001; Schmidt et al., 2007). Some authors (Cherubini et al., 2011;

CHERUBINI et al., 2011; Christensen et al., 2009; Levasseur et al., 2013; McDougall et al., 2001;

Schmidt et al., 2007) do not consider the impact of the emitted biogenic CO2 because it forms part of

the renewable carbon cycle. On the other hand, Finnveden (Finnveden et al., 2000) reports that it

might be inappropriate to exclude the biogenic carbon from the GWP in the case processes dealing

with biogenic carbon in different ways are compared. In this study carbon dioxide emissions from

biogenic carbon are included in the estimates for GWP, because following the zero burden approach,

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our boundary stars when the waste becomes waste and we do not account for its previous life-cycle.

Furthermore, in a comparative analysis based on a defined waste stream amounts the biogenic carbon

would count the same in all scenarios and therefore it would not add any more information to the

results.

S.2. Life Cycle Inventory

S.2.1. Process descriptions and Life Cycle assessment assumptions

S.2.1.1. System expansion

Ferrous material is assumed to be substituted at a 1 to 0.51 rate and the recovered material is assumed

to be recycled by electric furnace processing, as reported by the Worldsteel LCA Methodology report

(World steel association, 2011). Non-ferrous metal is assumed to be substituted at a 1 to 0.6 rate. The

recovered aluminium is assumed to be recycled by clean scrap melting and casting, as reported in the

Environmental profile report for the Aluminium Industry (European Aluminium Association, 2013).

A sensitivity analysis on the substitution ratio of the metals recovered has been performed but the

variation in the results was negligible and the results have not been reported.

S.2.1.2. Transport

For scenarios 1-2 MSW is assumed to be transported from transfer station to the processing plants (50

km distance) but the transport of the mechanically separated fraction to landfill/incineration is not

considered. The environmental burden due to the use of truck has been allocated to the direct burden

of the mechanical treatement plant and the diesel production has been allocated to the indirect burden

of this plant.

For scenario 3-4, source separated biodegradable waste is assumed to be transported from kerbside to

the AD plant (50 km distance) and the residual waste is assumed to be transported from transfer

station to incineration/landfill (50 km distance). The environmental burdens due to the use of truck

and production of diesel have been allocated to the section of incineration/landfill for the 75 %

(amount of residual waste) and for the 35% (amount of source separated waste) to the digester and

pre-treatment section of the anaerobic digestion plant.

For scenarios 5 MSW is assumed to be transported from transfer station to the advacend thermal

treatment process (50 km distance).

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All waste is assumed to be transported in an EURO 4-22t payload truck. The burden due to transport

(including the diesel production) is always less than 5% of the total environmental burden of the

processes, therefore, no sensitivity analysis has been performed on this parameter.

S.2.1.3. Incineration

Waste incineration is modelled according to average data for UK waste-to-energy plants taken from

the database of GaBi 5.0 software (Thinkstep, 2015). Two different incineration models are used,

respectively with wet and dry flue gas treatment (FGT). Different NOx-removal technologies are used

to represent the application of different FGT systems in Europe; the data from GaBi represent

averages over a number of European incinerators. The system includes generation of steam to produce

electricity and heat.

S.2.1.4. Landfill

The inventory data for landfilling with electricity recovery were based on the GaBi database

(Thinkstep, 2015). The data set represent a typical municipal waste landfill with surface and basic

sealing, meeting European limits for emissions. The site operations include landfill gas treatment,

leachate treatment, sludge treatment and deposition. Part of the landfill gas is assumed to be flared

(22%), part of it to be used for electricity production (28%) and the rest emitted to the environment

(50%). All manufacturing processes of the sealing materials, as well energy requirements for the site,

were included within the system.

S.2.2. Advanced thermal treatment: dual stage gasification and plasma process

Avoided burdens are allocated to the production of Plasmarok as it can be used as substitute of

aggregate materials (Korre and Durucan, 2009). We assume that Plasmarok substitutes the production

of primary aggregates from crushed rock as this is the most important source of primary aggregates in

England (Mankelow et al., 2011). We assume that the oxygen supplied to the process is produced

using the technology of cryogenic separation of air. Average UK data are applied (Thinkstep, 2015).

The inventory for the activated carbon used to remove the APC residue is reported in Noijuntira et al.

(Noijuntira and Kittisupakorn, 2010).

A wet scrubbing system is used in the dual stage advanced process to further cool and clean the

syngas from acid and alkali compounds. As the physical and chemical composition of the liquid

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effluents of this process do not exceed the limits reported in the WID directive (European Parliament,

2000), we assume that water effluents are treated in standard waste water treatment plants (Thinkstep,

2015).

The inventory and the environmental burden of all chemicals used in the process (such as nitrogen,

sodium hypochlorite, urea etc.) are reported in GaBi 6 LCA software (Thinkstep, 2015) and in

Ecoinvent (Swiss Centre for Life Cycle Inventories, 2014). The production of Bio-SNG is considered

according to Table 1.

S.2.3. Anaerobic Digestion of centrally separated waste

Six operations are identified in the AD process: i) pre-treatment; ii) anaerobic digestion; iii) water and

acid compounds removal; iv) upgrading of the biogas; v) disposal of digestate to incineration. The

characteristics of each section and the assumptions constituting the LCA models and the inventory

data are specified below.

Pre-treatment and anaerobic digestion phase (i and ii). After the mechanical separation of the

MSW, the biodegradable centrally separated waste (the composition of the biodegradable part

is reported in literature (Banks et al., 2011)) enters the pre-treatment section where the waste

undertakes maceration and hygienization. Further details of this phase (i.e. pre-treatment

steps, vessel dimensions, etc.) are reported in literature (Banks et al., 2011; Berglund and

Börjesson, 2006; Evangelisti et al., 2014). The AD phase is assumed to be using a continuous,

single-stage, mixed tank mesophilic reactor operating at a temperature of 35 ˚C in wet

condition given its broad application (Berglund and Börjesson, 2006; Evangelisti et al., 2014;

Monnet, 2003; Severn Wye Energy Agency, 2009). The majority of AD plants from centrally

separated biodegradable waste actually in use operate under this condition. Monson et al.

(Monson et al., 2007) reported that 73% of the anaerobic digesters treating centrally separated

MSW analyzed in their report use a wet system as well as 90% operate in mesophilic

temperature range. The yield of biogas produced during this phase decreases if the organic

fraction of centrally separated municipal solid waste is used instead of the source separated

fraction. This is due to the higher content of plastic and impurity of the organic matter

supplied to the digester and therefore a lower composition of volatile solid on which the yield

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of methane depends (Laraia, 2002). The yield of biogas is assumed to be 0.079 Nm3 per kg of

the centrally separated organic fraction (Monson et al., 2007). The model accounts also for

methane losses occurring in the digester (Berglund and Börjesson, 2006; Boldrin et al., 2011;

Dalemo et al., 1997; Fruergaard and Astrup, 2011), which are assumed to be 3 %.

Cleaning (water and H2S removal), up-grading and off gas flaring phase (iii and iv). The gas

has to be cleaned and upgraded before grid injection. The cleaning of the biogas includes

removal of H2S and water that can cause damages to the subsequent upgrading unit and to the

grid pipes. The most common method for H2S removal from the crude biogas is through the

reaction of H2S with metal oxides (Hagen and Polman, 2001; Persson, 2003). In this study

H2S is assumed to be removed in a desulphuriser unit with a catalytic bed of ZNO, which is

placed at the digester plant, where the biogas is produced. Water is assumed to be adsorbed

on silica gel in the upgrading unit in the pre-treatment phase. To achieve the strict regulation

limits set in the GMRS (GSMR, 1996), the raw methane is assumed to be upgraded in a

pressure swing adsorption system. Petersson et al. (Petersson, A. Wellinger, 2009) reported

that the PSA electricity consumption including gas compression to 7 barg is 0.25 Kwh/Nm 3 of

raw biogas. Persson et al. (Persson et al., 2006) assumed instead that the electricity

requirement for PSA was 0.5-0.6 Kwh/m3 of upgraded gas, not accounting for high pressure

compression (those are the figures reported by the owners), whereas Persson (Persson, 2003)

reported the same values as Persson et al. (Persson et al., 2006) for electricity requirements

not accounting for compression and specified that the electricity needs to be increased to the

values of 0.8-0.88 a Kwh/m3 of upgraded gas if compression is considered as well. The latter

value has been used in the LCA model. This value is in line with the value reported in the

Ecoinvent database (Swiss Centre for Life Cycle Inventories, 2014) for raw gas upgrading

(CH methane, 96% from biogas purification). The model accounts also for a 3% methane

losses (the amount of methane not recovered from the raw biogas, hence the methane content

of the off gas of the PSA system) occurring in the upgrading system (Patterson et al., 2011;

Persson et al., 2006; Petersson, A. Wellinger, 2009). The PSA model does not include the

production of a combustile stream for electricity production, as in literature this layout is not

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reported to be used for AD systems. The off gas of the PSA system is assumed to be flared

before emission to environment.

Digestate use (v). When anaerobic digestion is used to treat centrally separated organic wastes

the low quality of the digestate prevents from the use as fertiliser and it has to be disposed of

either by thermal treatment or landfill (Department of the Environment Heritage and Local

Government, 2006; Monson et al., 2007). In this study, the digestate produced in scenarios 1-

2 is assumed to be incinerated according to Ecoinvent database (Swiss Centre for Life Cycle

Inventories, 2014).

A sensitivity analysis on main parameters regarding the AD process has not been reported here as

significant results have already been published in Evangelisti et al. (Evangelisti et al., 2014).

S.2.4. Anaerobic Digestion of source separated waste and additional disposal

The whole digestate is assumed to be separated in liquor and fibre as standard practice (Wrap, 2012)

and the separation method is assumed to be physical (Wrap, 2010). The liquor is normally separated

using a separator or centrifuge to remove coarse fibres. The fibres represent 20 % of the total digestate

whereas the liquor is usually the 80% in weight of the total digestate (Wrap, 2012). To calculate the

nutrient of the liquor after dewatering the values for nutrient partition between liquid and solid phases

as reported in Lukehurst et al. (Lukehurst et al., 2010) are used. The electricity requirements for

dewatering are taken from Wiliams et al. (Wiliams and Esteves, 2011).

We assume that the liquor separated from the whole digestate in the dewatering section is used as

fertilizer whereas the fibres are sent to incineration as inert material (as reported in Wrap (Wrap,

2012)). The LCA model accounts for the burden associated with the use of liquor as fertilizer.

Organic fertilizers coming for example from the anaerobic digestion can be used to improve the

nutrient content of soils and therefore avoiding the use of chemical fertilizers (the use in agriculture of

fertilisers with high available nitrogen content, i.e. digestate, is anyway, affected by restrictions

according to the Nitrogen Vulnerable Zones as reported by the European Parliament (European

Parliament, 1991)).

We assume that the nutrients are not lost during the anaerobic digestion phase; thus all the nutrients of

the bio-degradable waste (N, K and P) remain in the whole digestate (Evangelisti et al., 2014; Møller

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et al., 2009). The nutrient content of the fertilizers is calculated based on the amounts of N, P 2O5 and

K2O for N, P and K, respectively (Defra, 2010), 2010). The distinction between readily availability

and crop availability of nutrient (Defra, 2012) is used to calculate the avoided chemical fertilizers and

the emissions due to fertilizer spreading.

The amount of readily available nutrients assumed in this study is reported in Wrap (Wrap, 2011)

(80% of the N content of the digestate is readily available and 100% of K2O and P2O5). Defra (Defra,

2010) reported the chemical fertilizers usually employed for N, K and P. The N readily available

content of the digestate is assumed to substitute the chemical fertilizer of ammonium sulphate, the

K2O readily available content of the digestate is assumed to substitute the chemical fertilizer of

potassium chloride and the readily available content of P2O5 of the digestate is assumed to substitute

the chemical fertilizer of the superphosphate. The results have been calculated equalling the amount

of nutrients readily available in the digestate to the amount of chemical fertilizer needed. (i.e. 1 kg of

N readily available in the digestate equal 1 kg of the chemical fertilizer NH4(SO2) substituted).

In the LCA model we have also accounted for the emission due to the organic fertilizers when those

are on the soil.

During the application of both chemical and organic fertilizers part of the nutrients is dispersed into

environment and is not crop available. This means that some amount of the readily available nutrient

might be lost as air emission (run off or evaporation), water leakage (leaching) or might not be readily

absorbed by the plants because chemically bound in a form of not easy uptake from plants. The

amount of the nutrients really uptaken by the crops is defined as the nutrient crop availability. Bruun

et al. (Bruun et al., 2006) reported the emission coefficients due to the use of the digestate as fertilizer.

In particular those emissions represented the difference between normal agricultural practice only

using inorganic fertilizers and use of digestate supplemented with inorganic fertilizers, according to

the Danish legislation. Those coefficients have already been used in some recent works (Boldrin et al.,

2011; Evangelisti et al., 2014; Møller et al., 2009). Nitrogen emissions from organic fertilizers are

higher than those of chemical fertilizers for two reasons: i) chemical fertilizers are given to the plants

when and where they need them and this reduces N evaporation; ii) not all the readily available N is

absorbed by the plants. The emissions associated with the spreading of fertilizers, either chemical or

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organic, are highly variable and depend strongly on the soil and weather conditions, spreading

practice and crop practice. Therefore, it is possible that the emission coefficients reported in Bruun et

al. (Bruun et al., 2006) do not exactly mirror the UK situation but as far as the author’s knowledge

these data are the only available. Wrap (Wrap, 2012) reported that they are undertaking studies on the

emission coefficients for digestate spreading applied to UK situation but no data have already been

released. New data on evaporation, leaching and loss of fertilisers might influence the results.

In the LCA model we also account for the part of the carbon of the feed waste not released as biogas.

Part of the carbon content of the liquor used as fertilizer is sequestered in the soil and not released to

the atmosphere as CO2 during the timeframe considered (Møller et al., 2009). This has been accounted

as an actual removal of CO2 from atmosphere and therefore as a negative contribution to the global

warming.

S.3.UK future energy scenarios: marginal electricity and natural gas

The marginal energy supply (in particular electricity supply), is reported to strongly affect the results

of an LCA analysis (Kløverpris et al., 2008; Moora and Lahtvee, 2009) and hence, a study of the

environmental burden of the technologies analysed have been performed according to different

marginal energy technologies.

The UK energy mixes (electricity mix and natural gas mix) are evolving towards renewables. National

Grid (National Grid, 2014) has foreseen possible future energy scenarios for the UK and has

undertaken a detailed analysis to 2035 for each scenario. Four scenarios have been identified: i) gone

green; ii) slow progression; iii) no progression; iv) low carbon life. Those scenarios are used by UK

National Grid ‘as a reference point for a range of modelling activities including network analysis to

identify potential gas and electricity network investment requirements in the future’. A brief

description is reported here.

i) ‘Gone Green is a future where more money is available, with strong policy and regulation

and new environmental targets. The economy is growing, and environmental

sustainability is not restrained by financial limitations as more money is available at both

an investment level for energy infrastructure and at a domestic level via disposable

income’.

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ii) ‘Slow Progression is a future where less money is available compared to Gone Green, but

with similar strong policy and regulation and new targets. Economic recovery is slower in

this scenario than in Gone Green and Low Carbon Life, resulting in investor uncertainty.

Financial constraints lead to difficult political decisions’.

iii) ‘No Progression is a future where there is less money available and less emphasis on

sustainability. There is slower economic recovery in this scenario, meaning less money is

available at both a government and consumer level. Government policy and regulation

remains the same as today, and no new targets are introduced’.

iv) ‘Low Carbon Life is a future where more money is available and there is less emphasis on

sustainability. There is higher economic growth. Society has more disposable income

which results in higher uptake of electric vehicles, and more renewable generation at a

local level. Government policy is focused on the long term’.

Based on those four possibilities, National Grid (National Grid, 2014) reports the mix of technologies

used in the UK to produce electricity and natural gas each year till 2035.

Table S1 reports some of the data published by National Grid (National Grid, 2014) regarding the

future energy mix. As an example, only few years (13-14, 20-21, 25-26 and 35-36) are reported for

the gone green scenario.

National Grid (National Grid, 2014) infers that the imports generic regarding the natural gas (see

Table S1) can be any mixture of the LNG and continental gas, ranging from all LNG to all continental

gas. In the LCA model, it is assumed that the generic imports of natural gas are completely supplied

by LNG as this is the most probable option.

The marginal technologies for the foreseen energy scenarios are modelled using Gabi database

(Thinkstep, 2015).

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ReferencesBallinger, A., Bewswick, C., Hogg, D., 2009. The Potential for Planning Policies to Influence the

Climate Change Impacts of Waste Management.Banks, C.J., Chesshire, M., Heaven, S., Arnold, R., 2011. Anaerobic digestion of source-segregated

domestic food waste: performance assessment by mass and energy balance. Bioresour. Technol. 102, 612–20. doi:10.1016/j.biortech.2010.08.005

Berglund, M., Börjesson, P., 2006. Assessment of energy performance in the life-cycle of biogas production. Biomass and Bioenergy 30, 254–266. doi:10.1016/j.biombioe.2005.11.011

Biobased Products Working Group, 2010. Principles for the accounting of biogenic carbon in product carbon footprint (PCF) standards. Ind. Biotechnol. 6, 318–320. doi:10.1089/ind.2010.6.318

Boldrin, A., Neidel, T.L., Damgaard, A., Bhander, G.S., Møller, J., Christensen, T.H., 2011. Modelling of environmental impacts from biological treatment of organic municipal waste in EASEWASTE. Waste Manag. 31, 619–30. doi:10.1016/j.wasman.2010.10.025

Bruun, S., Hansen, T.L., Christensen, T.H., Magid, J., Jensen, L.S., 2006. Application of processed organic municipal solid waste on agricultural land – a scenario analysis. Environ. Model. Assess. 11, 251–265. doi:10.1007/s10666-005-9028-0

Buttol, P., Masoni, P., Bonoli, A., Goldoni, S., Belladonna, V., Cavazzuti, C., 2007. LCA of integrated MSW management systems: case study of the Bologna District. Waste Manag. 27, 1059–70. doi:10.1016/j.wasman.2007.02.010

CHERUBINI, F., PETERS, G.P., BERNTSEN, T., STRØMMAN, A.H., HERTWICH, E., 2011. CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming. GCB Bioenergy 3, 413–426. doi:10.1111/j.1757-1707.2011.01102.x

Cherubini, F., Strømman, A.H., Hertwich, E., 2011. Effects of boreal forest management practices on the climate impact of CO2 emissions from bioenergy. Ecol. Modell. 223, 59–66. doi:10.1016/j.ecolmodel.2011.06.021

Christensen, T.H., Gentil, E., Boldrin, A., Larsen, A.W., Weidema, B.P., Hauschild, M., 2009. C balance, carbon dioxide emissions and global warming potentials in LCA-modelling of waste management systems. Waste Manag. Res. 27, 707–15. doi:10.1177/0734242X08096304

Coleman, T., Masoni, P., Dryer, A., McDougall, F., 2003. International expert group on Life Cycle assessment for integrated waste management. Int. J. Life Cycle Assess. 8, 175–178. doi:10.1007/BF02978465

Dalemo, M., Sonesson, U., Björklund, A., Mingarini, K., Frostell, B., Jönsson, H., Nybrant, T., Sundqvist, J.-O., Thyselius, L., 1997. ORWARE – A simulation model for organic waste handling systems. Part 1: Model description. Resour. Conserv. Recycl. 21, 17–37. doi:10.1016/S0921-3449(97)00020-7

Defra, 2012. Answering farmers questions on using digestate and compost.Defra, 2010. RB209 Fertiliser Manual [WWW Document]. URL

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69469/rb209-fertiliser-manual-110412.pdf (accessed 2.24.15).

Department of the Environment Heritage and Local Government, 2006. National Strategy on Biodegradable Waste.

European Aluminium Association, 2013. Environmental Profile Report for the European Aluminium Industry: Life Cycle Inventory Data for Aluminium Production and Transformation Process in Europe.

European Parliament, 2000. Directive 2000/76/EC of the European Parliament and of the Council of 4 December 2000 on the incineration of waste (OJ L332, P91 - 111)-WID.

European Parliament, 1991. Directive 91/676/EEC of 12 December 1991 concerning the protectionof waters against pollution caused by nitrateds from agricultural sources.

Evangelisti, S., Lettieri, P., Borello, D., Clift, R., 2014. Life cycle assessment of energy from waste via anaerobic digestion: a UK case study. Waste Manag. 34, 226–37. doi:10.1016/j.wasman.2013.09.013

Finnveden, G., Johansson, J., Lind, P., Moberg, Å., 2000. Life Cycle Assessments of Energy from Solid Waste.

Fruergaard, T., Astrup, T., 2011. Optimal utilization of waste-to-energy in an LCA perspective. Waste Manag. 31, 572–82. doi:10.1016/j.wasman.2010.09.009

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2122

GSMR, 1996. HEALTH AND SAFETY Gas Safety ( Management ) Regulations 1996.Guinée, J.B., 2002. Handbook on Life Cycle Assessment, Operational Guide to the ISO Standards,

Kluwer Aca. ed.Hagen, M., Polman, E., 2001. Adding gas from biomass to the gas grid [WWW Document]. URL

http://gasunie.eldoc.ub.rug.nl/FILES/root/2001/2044668/2044668.pdfIPCC, 2006. 2006 IPCC guidelines ofr national greenhouse gas inventories [WWW Document]. URL

http://www.ipcc-nggip.iges.or.jp/support/Primer_2006GLs.pdfKløverpris, J., Wenzel, H., Nielsen, P.H., 2008. Life cycle inventory modelling of land use induced by

crop consumption. Int. J. Life Cycle Assess. 13, 13–21. doi:10.1065/lca2007.10.364Korre, A., Durucan, S., 2009. Life Cycle Assessment of Aggregates [WWW Document]. URL

http://www.wrap.org.uk/sites/files/wrap/EVA025-MIRO Life Cycle Assessment of Aggregates final report.pdf

Laraia, R., 2002. Il trattament anaerobic dei rifiuti.Levasseur, A., Lesage, P., Margni, M., Samson, R., 2013. Biogenic Carbon and Temporary Storage

Addressed with Dynamic Life Cycle Assessment. J. Ind. Ecol. 17, 117–128. doi:10.1111/j.1530-9290.2012.00503.x

Lukehurst, C.T., Frost, P., Al Seadi, T., 2010. Utilization of digestate from biogas plants as biofertilizer.

Mankelow, J.M., Sen, M.A., Wrighton, C.E., Idoine, N., 2011. Collation of the results of the 2009 aggregate minerals survey for England and Wales [WWW Document]. URL https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/6366/1909597.pdf

McDougall, F., White, P., Franke, M., Hindle, P., 2001. Integrated Solid Waste Management. Blackwell Publishing Company, Oxford, UK. doi:10.1002/9780470999677

Møller, J., Boldrin, A., Christensen, T.H., 2009. Anaerobic digestion and digestate use: accounting of greenhouse gases and global warming contribution. Waste Manag. Res. 27, 813–24. doi:10.1177/0734242X09344876

Monnet, F., 2003. An Introduction to Anaerobic Digestion of Organic Wastes [WWW Document]. URL http://www.biogasmax.co.uk/media/introanaerobicdigestion__073323000_1011_24042007.pdf

Monson, K.D., Esteves, S.R., Guwy, A.J., Dinsdale, R.., 2007. Anaerobic digestion of biodegradable Municipals wastes A review [WWW Document]. URL http://www.walesadcentre.org.uk/Controls/Document/Docs/Anaerobic Digestion of BMW _compressed_ - A Review _for print_.pdf (accessed 2.24.15).

Moora, H., Lahtvee, V., 2009. ELECTRICITY SCENARIOS FOR THE BALTIC STATES AND MARGINAL ENERGY TECHNOLOGY IN LIFE CYCLE ASSESSMENTS -- A CASE STUDY OF ENERGY PRODUCTION FROM MUNICIPAL WASTE INCINERATION. Oil Shale 26, 331–346.

National Grid, 2014. UK Future Energy Scenarios [WWW Document]. URL http://www2.nationalgrid.com/uk/industry-information/future-of-energy/future-energy-scenarios/

Noijuntira, I., Kittisupakorn, P., 2010. Life Cycle Assessment for the Activated Carbon Production by Coconut Shells and Palm-Oil Shells, in: The 2nd RMUTP International Conference 2010. pp. 228–231.

Patterson, T., Esteves, S., Dinsdale, R., Guwy, A., 2011. Life cycle assessment of biogas infrastructure options on a regional scale. Bioresour. Technol. 102, 7313–23. doi:10.1016/j.biortech.2011.04.063

Persson, M., 2003. Evaluation of upgrading techniques for biogas [WWW Document]. doi:SGC142Persson, M., Wellinger, A., Rehnlund, B. Rahm, L., Hugosson, B., 2006. Report on technological

applicability of existing biogas upgrading processes [WWW Document]. URL http://www.biogasmax.eu/media/report_on_technological_2007__041639600_1025_22052007.pdf (accessed 2.24.15).

Petersson, A. Wellinger, A., 2009. Biogas upgrading technologies- developments and innovations [WWW Document]. URL http://www.iea-biogas.net/files/daten-redaktion/download/publi-task37/upgrading_rz_low_final.pdf (accessed 2.24.15).

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Schmidt, J.H., Holm, P., Merrild, A., Christensen, P., 2007. Life cycle assessment of the waste hierarchy--a Danish case study on waste paper. Waste Manag. 27, 1519–30. doi:10.1016/j.wasman.2006.09.004

Severn Wye Energy Agency, 2009. BIOGAS REGIONS An Introduction to Biogas and Anaerobic Digestion A guide for England and Wales [WWW Document]. URL http://www.severnwye.org.uk/downloads/Biogas_Brochure.pdf

Swiss Centre for Life Cycle Inventories, 2014. Ecoinvent: the life cycle inventory data, Version 3.0. Swiss Centre for Life Cycle Inventories, Duebendorf.

Thinkstep, 2015. GaBi 6 software-system and databases for life cycle engineering. Stuttgart, Echterdingen (see www.pe-europe.com).

Wiliams, J., Esteves, S., 2011. Digestates: Characteristics, Processing and Utilisation.World steel association, 2011. Methodology Report: Life Cycle Inventory Study for Steel Products.Wrap, 2012. Enhancement and treatment of digestates from anaerobic digestion [WWW Document].

URL http://www.wrap.org.uk/sites/files/wrap/Digestates from Anaerobic Digestion A review of enhancement techniques and novel digestate products_0.pdf

Wrap, 2011. Digestate & Compost in Agriculture, Bulletin 2 – November 2011. Beat rising cost of fertiliser and extreme weather by using digestate and compost [WWW Document]. URL http://www.wrap.org.uk/sites/files/wrap/Bulletin 2 - agronomic benefits_0.pdf

Wrap, 2010. Specification for whole digestate, separated liquor and separated fibre derived from the anaerobic digestion of source-segregated biodegradable materials [WWW Document]. URL http://www.wrap.org.uk/sites/files/wrap/PAS110_vis_10.pdf (accessed 2.24.15).

13

384385386387388389390391392393394395396397398399400401402403404405406

2526

UK electricity grid mix[%] 2013/14 2020/21 2025/26 2035/36

Nuclear 0.181992 0.1750140.11747

7 0.163797

Coal 0.38821 0.0519680.03726

2 0.004331Gas 0.214257 0.313289 0.28323 0.127476

CCS Coal 0 00.00825

4 0.065028CCS Gas 0 0 0 0.073832Imports 0.05169 0.107407 0.03405 0.008322

Wind 0.088052 0.224610.37546

4 0.398648

Solar 0.005019 0.0172080.02462

3 0.036622Biomass 0.031754 0.065839 0.06928 0.056445

Other Renewables 0.018442 0.0226610.02466

9 0.030114

Hydro/Pumped Storage/Marine 0.020399 0.0218430.02553

7 0.035256

Oil/Others 0.000187 0.0001610.00015

3 0.000129Natural gas UK mix

[%]        UKCS 2013 2020 2025 2035

Norway 0.421694 0.4570970.35211

4 0.156376

Shale 0.354716 0.320640.29230

4 0.286783

Biomethane 0 00.05792

8 0.247799CBM 9.88E-05 0.007522 0.01815 0.052077

Continent 0 0.0081370.01181

3 0.013523

LNG 0.106354 0.0323120.01924

3 0.007681

Import Generic 0.117137 0.0394530.03979

1 0.045552

Demand 0 0.1348390.20865

7 0.190209

Table S1: Foreseen energy mixes in the UK according to National Grid (National Grid, 2014).

Normalization factor  EU25+3, year 2000. CML, IPCC, ReCiPe (person equivalents)  CML2001 - Apr. 2013, Abiotic Depletion (ADP elements) 6040000CML2001 - Apr. 2013, Abiotic Depletion (ADP fossil) 3.51E+13CML2001 - Apr. 2013, Acidification Potential (AP) 1.68E+10CML2001 - Apr. 2013, Eutrophication Potential (EP) 1.85E+10CML2001 - Apr. 2013, Freshwater Aquatic Ecotoxicity Pot. (FAETP inf.) 2.09E+11CML2001 - Apr. 2013, Global Warming Potential (GWP 100 years) 5.21E+12

14

407

408409

2728

CML2001 - Apr. 2013, Global Warming Potential, excl biogenic carbon (GWP 100 years) 5.21E+12CML2001 - Apr. 2013, Human Toxicity Potential (HTP inf.) 5E+11CML2001 - Apr. 2013, Marine Aquatic Ecotoxicity Pot. (MAETP inf.) 4.45E+13CML2001 - Apr. 2013, Ozone Layer Depletion Potential (ODP, steady state) 10200000CML2001 - Apr. 2013, Photochem. Ozone Creation Potential (POCP) 1.73E+09CML2001 - Apr. 2013, Terrestric Ecotoxicity Potential (TETP inf.) 1.16E+11

Table S2: Impact values used for normalisation. The normalisation is done based on CML, IPCC, ReCiPe (region equivalents), EU25+3, year 2000 (Thinkstep, 2015).

Normalised results

  S.1 S.2 S.3 S.4 S.5

Abiotic Depletion (ADP elements) [kg Sb-Equiv.] -7.00449E-14 4.92193E-15 -4.4064E-13 -1.25636E-143.45E-

14

Abiotic Depletion -6.66487E-14 -2.714E-14 -6.5113E-14 -1.34569E-14-9.1E-

14

Acidification Potential -3.3403E-14 -1.6067E-14 -9.8073E-15 1.31538E-141.95E-

14

Eutrophication Potential 1.98249E-14 3.4767E-14 2.48966E-14 4.02271E-144.21E-

15

Freshwater Aquatic Ecotoxicity Pot. 1.09476E-13 1.10582E-13 -1.0807E-14 -9.49733E-152.27E-

14

Global Warming Potential 9.32546E-14 1.71507E-13 1.04598E-13 1.87681E-131.38E-

13

Global Warming Potential, excl biogenic carbon -3.53443E-14 6.27702E-14 -2.4001E-14 8.81235E-149.23E-

15

Human Toxicity Potential -8.12672E-14 -7.6677E-14 -8.4066E-15 -4.02202E-15-6.3E-

14

Marine Aquatic Ecotoxicity Pot. -2.68149E-12 -2.9049E-12 5.1791E-13 2.16172E-13-2.7E-

12

Ozone Layer Depletion Potential 2.7674E-16 1.7921E-16 2.95602E-16 4.02731E-179.02E-

17

Photochem. Ozone Creation Potential -2.4393E-14 5.28661E-14 -1.6495E-14 7.07699E-14 -1E-14

Terrestric Ecotoxicity Potential -7.73728E-16 3.2548E-15 -2.1158E-16 3.73001E-151.32E-

15

Table S3: Normalised results.

2013-2

014

2016-2

017

2019-2

020

2022-2

023

2025-2

026

2028-2

029

2031-2

032

2034-2

035

0.0E+01.0E-12.0E-13.0E-14.0E-15.0E-16.0E-17.0E-18.0E-19.0E-11.0E+0

Slow progression

S.1 S.5 S.3

Glo

bal W

arm

ing

Pote

ntia

l [kg

CO

2-E

quiv

.]

2013-2

014

2016-2

017

2019-2

020

2022-2

023

2025-2

026

2028-2

029

2031-2

032

2034-2

035

0.0E+01.0E-12.0E-13.0E-14.0E-15.0E-16.0E-17.0E-18.0E-19.0E-11.0E+0

Low carbon life

S.1 S.5 S.3

Glo

bal W

arm

ing

Pote

ntia

l [kg

CO

2-E

quiv

.]

15

410411

412

413

414

2930

Figure S.1. Fossil GWPs of S.1, S.3 and S.5 for future electricity and natural gas UK mix according to

the a) slow progression scenario; b) Low carbon life scenario. Results are reported for 1 MJ of

methane as functional unit.

20

13-201

4

2016-2

017

2019-2

020

2022-2

023

2025-2

026

2028-2

029

2031-2

032

2034-2

035

0.0E+01.0E-12.0E-13.0E-14.0E-15.0E-16.0E-17.0E-18.0E-1

Slow progression

S.1 S.5 S.3

Glo

bal W

arm

ing

Pote

ntia

l [kg

CO

2-E

quiv

.]

20

13-201

4

2016-2

017

2019-2

020

2022-2

023

2025-2

026

2028-2

029

2031-2

032

2034-2

035

0.0E+01.0E-12.0E-13.0E-14.0E-15.0E-16.0E-17.0E-18.0E-1

Low carbon life

S.1 S.5 S.3G

loba

l War

min

g Po

tent

ial [

kg C

O2-

Equ

iv.]

Figure S.2. GWPs of S.1, S.3 and S.5 for future electricity and natural gas UK mix according to the a)

slow progression scenario; b) Low carbon life scenario. Results are reported for 1 kg of MSW as

functional unit.

16

415

416

417

418

419

420

421

422

423

3132