Environmentally Sustainable Utilization of Waste Resources for Energy Production

8/16/2019 Environmentally Sustainable Utilization of Waste Resources for Energy Production

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Environmentally sustainable utilization of waste

resources for energy production

Thilde Fruergaard

DTU EnvironmentDepartment of Environmental Engineering

Technical University ofDenmark

PhD ThesisMarch2010



Environmentally sustainable utilization of

waste resources for energy production

Thilde Fruergaard

PhD Thesis

March 2010

Department of Environmental Engineering

Technical University of Denmark ilde Fruergaard

vironmentally sustainable utilization of waste resources for energy production



D Thesis, March 2010

e thesis will be available as a pf!file for ownloaing from the homepage of the epartment" www#env#t$#k

http://www.env.dtu.dk/




1

Preface

The work reporte in this PhD thesis entitle %Environmentally s$stainable

$tili&ation of waste reso$rces for energy pro$ction' was carrie o$t at the

Department of Environmental Engineering at the Technical University of

Denmark (DTU) from *$g$st 200+ to an$ary 2010# The thesis was s$pervise by

Professor Thomas -o.l$n /hristensen an f$ne 1 by DTU an 2 by the

Danish /o$ncil for trategic 3esearch#

The content of the thesis is base on si4 scientific .o$rnal papers prepare in

collaboration with internal an e4ternal partners# The papers are in the te4t

referre to by the name of the a$thors an their appeni4 n$mber written with

3oman n$merals, e#g# 5r$ergaar et al# (6)#

6 5r$ergaar, T#, Ekvall, T# 7 *str$p, T# (2008)" Energy $se an recovery in

waste management an implications for acco$nting of greenho$se gases

*ress" DTU EnvironmentDepartment of Environmental Engineering TechnicalUniversity of Denmark Mil.oeve., b$iling 11 D9!

2:00 9gs# ;yngby Denmark

Phone reception" Phonelibrary" 5a4"

<=> =>2> 1+00 <=> =>2> 1+10 <=> =>8 2:>0

-omepage"

E!mail"

http"www#env#t$#k

reception?env#t$#k Printe by"

@ester 9opi @ir$m, March 2010

/over" Torben Dolin

6AB" 8C:!:C!81:>>!:=!8


mailto:[email protected]





2

an global warming contrib$tions# aste Management 7 3esearch, 2C,

C2=!CC#

66 Mathiesen, A#@#, Mnster, M# 7 5r$ergaar, T# (2008)" Uncertainties

relate to the ientification of the marginal energy technology in

conseF$ential life cycle assessments# o$rnal of /leaner Pro$ction, 1C,

11!1:#

666 5r$ergaar, T#, /hristensen, T#-# 7 *str$p, T# (2008)" Energy recovery

from waste incineration" *ssessing the importance of istrict heating

networks# ($bmitte to aste Management)#

6@ 5r$ergaar, T# 7 *str$p, T# (2010)" Gptimal $tili&ation of waste to energy

in an ;/* perspective# ($bmitte to aste Management)#

@ *str$p, T#, Moller, # 7 5r$ergaar, T# (2008)" 6ncineration an co!

comb$stion of waste" acco$nting of greenho$se gases an global warming

contrib$tions# aste Management 7 3esearch, 2C, C:8!C88#

@6 Damgaar, *#, 3iber, /#, 5r$ergaar, T#, -$lgaar, T# 7 /hristensen, T#-#(2010)" ;ife!cycle!assessment of the historical evelopment of air

poll$tion control an energy recovery in waste incineration# (Man$script)#

The papers are not incl$e in this www!version b$t can be obtaine from the

library at DTU Environment# /ontact info" ;ibrary, Department of

Environmental Engineering, Technical University of Denmark, Mil.oeve.,

A$iling 11, D9!2:00 9gs# ;yngby, Denmark or library?env#t$#k #

March 2010

Thile 5r$ergaar





Acknowledgements

5irst of all 6 wo$l like to thank my s$pervisor, Professor Thomas -# /hristensen

for his g$iance thro$gho$t the PhD pro.ect# 6 am gratef$l for his s$pport, his

professionalism an his ability to always keeping a sense of perspective#

econly, 6 wo$l like to thank the many people 6 have collaborate with $ring

my pro.ect an whose effort 6 highly appreciate"

H Thomas *str$p for his always skillf$l g$iance, enco$ragement an

professional competency

H Marie Mnster from *alborg University for her enth$siasm an val$able

isc$ssions abo$t ;/* an energy system moeling# Arian @a Mathiesen

an -enrik ;$n from *alborg University as well as Po$l Erik Morthorst

from 3ise DTU for enlightening me on energy systems an renewable

energy aspects

H Irethe -.ortbak from Jrh$s 9omm$ne an the many other people in the

m$nicipal waste aministrations an the operational $nits who have

provie me with ata an patiently answere my many F$estions

6 wo$l also like to give thanks to all my colleag$es in the oli aste 3esearch

gro$p for fr$itf$l isc$ssions, e4cellent cooperation an for creating a nice an

inspiring working environment# * special thanks is e4tene to my office mates,

ol as new" *nna arberg ;arsen, iff -yks, acob 9ragh *nersen, ;ine

Arogaar an /hristiane Gros for being s$ch goo companyK The PhD cl$b an

all my other colleag$es at DTU Environment are greatly acknowlege for

creating a warm an pleasant atmosphere# Thanks to *nne -arsting for always

being very helpf$l an thanks to Torben Dolin an ;isbet Ar$senorff from thegraphic office for making all the ill$strations in my papers an the thesis#

;ast b$t not least, thanks to family an friens for all yo$r s$pport thro$gho$t the

years an the interest yo$ have shown in the worl!of!wasteK Thank yo$ Thomas

for yo$r love, for always believing in me an for yo$r $nconitional s$pport,

especially $ring the last months of the pro.ect#



Lv



Summary

Energy recovery from waste is a highly prioriti&e treatment option in Denmark,

an energy from waste acco$nts for appro4imately 20 of the ann$al heat

pro$ction an = of the electricity pro$ction# Utili&ation of other f$el types

wo$l be necessary if waste was not available for energy pro$ction# To eval$ate

the environmental impacts of energy recovery from waste, the interactions with

the energy system have to be ientifie as the s$bstit$tion of other f$els may have

profo$n effects on the o$tcome# 6entification of energy s$bstit$tion is f$rther

relate to the overall framework of the assessment, i#e# efinition of the goal an

scope# The main aim of this PhD thesis was to provie a systematic framework for

life cycle assessment (;/*) moeling of waste!to!energy technologies#

This thesis incl$e the following main activities"

H Establishment of a framework for acco$nting of greenho$se gases relate to

energy $se an recovery within waste management# $ch a framework was

also establishe for waste incineration an co!comb$stion in a st$y

assessing the importance of irect greenho$se gas emissions relative to

inirect emissions#H *ssessment of the $ncertainties relate to ientification of the marginal

technology for electricity pro$ction# This incl$e a review of

evelopments in marginal technologies from a historical perspective, a

s$rvey foc$sing on how the marginal technology was ientifie an assesse

in ifferent st$ies, an an energy system moeling of the Danish energy

system eval$ating the conseF$ences of increase waste incineration in a

(f$t$re) short!term perspective#

H Eval$ation of the importance of local conitions for F$antifying theenvironmental conseF$ences of waste incineration with energy recovery#

Two specific istrict heating networks were $se as basis for the assessment

foc$sing on important esign an operational properties of the other heat

pro$cing facilities in the network to which the waste incinerator was

connecte#

H ;/* of three waste!to!energy technologies treating two ifferent types of

waste" organic ho$sehol waste an soli recovere f$el (35)# *naerobic



igestion was eval$ate as treatment metho for organic ho$sehol waste,

an co!comb$stion at a coal!fire power plant was eval$ate as treatment

metho for 35# Aoth waste fractions were compare with waste

incineration with an witho$t energy recovery#

H ;/* of the historical evelopment of air poll$tion control technologies for

waste incinerators an the importance of energy s$bstit$tion in this conte4t#

Aase on these activities the following goal an scope relate factors were

ientifie as critical to ens$re transparency an consistency in ;/* st$ies of

waste!to!energy technologies" 1) goal efinition, 2) the ;/* approach, ) the

scale of the change, =) the time perspective, >) the technological an +) thegeographical scope, an C) the effects of the /G2 emission traing scheme# *lso

the type of effects (short!term or long!term) incl$e in the ;/* was ientifie as

critical for the o$tcome# 6t was recommene to foc$s on etermining the long!

term effects, i#e# ecisions affecting investments in pro$ction capacity# *s f$t$re

effects are associate with s$bstantial $ncertainties, it was recommene to test

the importance of energy s$bstit$tion for the ;/* res$lts by $sing two

significantly ifferent technologies# in an coal were recommene for

electricity pro$ction, an biomass an coal (or another type of fossil f$elepening on the local conitions) for heat pro$ction#

everal contrib$tions besies energy s$bstit$tion were ientifie as significant for

the res$lts of an ;/* of waste!to!energy technologies# The to4ic impact

categories were heavily infl$ence by emissions of heavy metals relate to the

chemical composition of the waste an the technology consiere# *ss$mptions

concerning the final isposal of igestate from anaerobic igestion were important

for n$trient enrichment as well as the to4ic impact categories#

3ecommenations for treatment of comb$stible waste in Denmark epene to

some e4tent on the foc$s of the assessment# -owever, waste incineration with

energy recovery prove to be the best alternative in the ma.ority of impact

categories provie all heat co$l be $tili&e#



Dansk sammenfatning

Energi$nyttelse af affal er h0 .t prioriteret i Danmark, og affalsbaseret energi

$g0r ca# 20 af en pro$ceree varme og = af elektriciteten# -vis ikke

affal var tilgsngeligt for energi$nyttelse sk$lle anre brsnsler anvenes i

steet# 6 en eval$ering af e mil.0msssige pNvirkninger af energi$nyttelse af

affal er et vigtigt at tage h0 .e for $vekslingerne me energisystemet, a isse

kan have stor betyning for res$ltatet# Det samme gsler for e faktorer, er

efinerer $ners0gelsens rammer, vs# efinition af mNlsstning og afgrsnsning#

5ormNlet me enne ph!afhanling var at fastlsgge e n0venige

rammebetingelser for livscykl$sv$reringer (;/*) af affalsbaseree

energiteknologier#

*fhanlingen har omfattet e f 0lgene aktiviteter"

H Etablering af rammebetingelser for opg0relse af rivh$sgasser relateret til

energiforbr$g og energigenvining i affalshNntering# ;ignene

rammebetingelser var etableret for affalsforbrsning og meforbrsning i

et st$i$m, er kortlage betyningen af e irekte emissioner af

rivh$sgasser i forhol til e inirekte#H En $ners0gelse af $sikkerheerne knyttet til ientificering af en

marginale teknologi for pro$ktion af elektricitet# Dette st$i$m omfattee

en gennemgang af $viklingen i marginale teknologier set i et historisk

perspektiv, en $ners0gelse af fremgangsmNen for at bestemme en

marginale teknologi i en rskke st$ier samt en energisystemanalyse af e

(fremtiige) kortsigtee konsekvenser af 0get affalsforbrsning i Danmark#

H En eval$ering af betyningen af lokale forhol for en kvantificering af e

mil.0msssige konsekvenser af affalsforbrsning me energi$nyttelse#Uners0gelsen var baseret pN to specifikke f.ernvarmenet, og fok$s for

$ners0gelsen var betyningen af e konstr$ktions! og riftsmsssige

parametre af e anre varmeteknologier ligelees tilsl$ttet f.ernvarmenettet#

H En ;/* af tre affalsbaseree teknologier til behanling af to typer affal"

organisk h$sholningsaffal og energirige affalsfraktioner (3D5)#

Aioforgasning var eval$eret som behanlingsmetoe for et organiske

h$sholningsaffal, og meforbrsning pN et k$lfyret kraftvsrk var



$ners0gt for 3D5# 5or begge affalstyper blev affalsforbrsning me og

$en energi$nyttelse br$gt som reference#

H En ;/* af en historiske $vikling af r 0ggasrensningsteknologier for

forbrsningsanlsg samt betyningen af energi$nyttelse#

Aaseret pa isse aktiviteter blev f 0lgene mNlsstnings! og afgrsnsningsrelateree

faktorer ientificeret som vsrene kritiske i forhol til at sikre gennemsigtighe og

sammenhsng i ;/* st$ier af affalsbaseree energiteknologier" 1) efinition af

mNlsstning, 2) ;/*!tilgangen, ) omfanget af snringen, =) tisperspektivet, >)

en teknologiske og +) en geografiske afgrsnsning og C) effekterne af et

e$ropsiske /G2 kvotesystem# GgsN typen af e inkl$eree effekter (kortsigteeeller langsigtee) blev ientificeret som vsrene kritiske# Det blev anbefalet at

fok$sere pN e langsigtee effekter, vs# e investeringsmsssige effekter# Da

fremtiige effekter er behsftet me stor $sikkerhe, blev et anbefalet at teste

betyningen af energis$bstit$tion for ;/*Oens res$ltater ve at anvene to

signifikant forskellige teknologier# Det blev anbefalet at benytte k$l og vin for

elektricitetspro$ktion samt biomasse og k$l (eller et anet fossilt brsnsel

afhsngigt af e lokale forhol) for pro$ktion af varme#

Uover energis$bstit$tion blev askillige birag ientificeret som vigtige for

res$ltaterne af en ;/* af affalsbaseree teknologier# Emissioner af t$ngmetaller

relateret til affalets kemiske sammensstning og en specifikke teknologi have

stor betyning for e toksiske pNvirkningskategorier# *ntagelser ver 0rene

behanlingen af rNneresten fra biogasprocessen var vigtige i forhol til

nsringssaltsbelastning og e toksiske pNvirkningskategorier#

*nbefalinger for behanling af en brsnbare affalsfraktion i et ansk perspektiv

afhang i nogen gra af $ners0gelsens fok$s# 6kke esto minre var

affalsforbrsning me energi$nyttelse et beste alternativ i hoveparten af

pNvirkningskategorier, for$sat at al varme k$nne $nyttes#

Table of contents

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4



1

1Introduction

The increase foc$s on energy reso$rces an climate has altere the perception of

waste# aste prevention is still the main goalQ nevertheless, it is now generallyaccepte that waste may be beneficial to the environment provie the waste is

manage properly# -owever, etermining whether or not a given waste

management option is beneficial is not a straightforwar task as many parameters

infl$ence the res$lts# The waste management system is not an isolate $nit b$t

interacts with the s$rro$nings" especially interactions with the energy system

have a profo$n effect# *s $tili&ation of waste for energy pro$ction has high

priority in the Danish waste management system, assessing these interactions an

e4plaining their conseF$ences are the focal points of this thesis#

1.1 Waste based energy production in Denmark

@ario$s waste!to!energy technologies e4ist toay, s$ch as waste incineration,

anaerobic igestion, gasification, etc# Mass b$rn incineration is the most common#

Denmark is one of the co$ntries in E$rope where waste incineration with energy

recovery percentage!wise constit$tes the largest part of the waste treatment

options# *ccoring to the Danish Environmental Protection *gency, >: of theho$sehol waste was incinerate in 200+, recycle an 8 lanfille

(DEP*, 200:)# aste incineration was also a ominant treatment metho for

waste from the service sector (=> incinerate), b$t less significant for the

in$strial sector (1= incinerate)# 6n total, #> million tonnes of waste was

incinerate in 200+# * main reason for the wiesprea istrib$tion of waste

incineration in Denmark is a ban on lanfilling of comb$stible waste which

became effective in an$ary, 188C (Mil.oministeriet, 188>)# This ban relocate

comb$stible waste from lanfills to incineration plants, an is the reason why

waste incineration rather than lanfilling is $se as frame of reference for new

waste technologies in Denmark#

*nother reason for the wiesprea istrib$tion of waste incineration can be fo$n

in the esign of the energy system, more specifically the wiely istrib$te istrict

heating networks facilitating $tili&ation of vario$s types of inhomogeneo$s f$els

s$ch as m$nicipal soli waste (M) as well as s$rpl$s heat from in$stries# The



2

istrict heating networks s$pply heat to aro$n 2 of the Danish pop$lation# The

first incineration plant in Denmark was commissione in 180 an was only

pro$cing heat, while some of the plants b$ilt in the following years generate

steam for both heat an power pro$ction (9leis 7 Dalager, 200=)# 5or a perio

of 2> years the plants commissione pro$ce heat only, b$t from 1880 all new

incineration plants have provie combine heat an power pro$ction (9leis 7

Dalager, 200=)# Toay, Denmark is eF$ippe with 0 waste incinerators with an

average net energy efficiency of :> base on the net calorific val$e# 20 % is

generate as electricity an +> as heat (DE* et al#, 200>)#

Energy recovere from waste acco$nte in 200C for aro$n 20 of the Danishheat pro$ction an = of the electricity pro$ction (DE*, 200:)# aste

incineration acco$nte for appro4imately 8: of the generate energy an

anaerobic igestion for 2 #

1.2 !aluation of waste management options

Different assessment methos e4ist which can be $se for eval$ation of waste

management systems# ome methos foc$s on environmental performance

whereas others foc$s on economic aspects# Different methos may also becombine to provie a more comprehensive s$rvey# Environmental impact

assessment (E6*), strategic environmental assessment (E*), life cycle

assessment (;/*), risk assessments, energy system analysis (E*) an material

flow acco$nting (M5*) are e4amples of methos foc$sing on environmental

aspects anor reso$rces, whereas cost benefit analysis (/A*) an life cycle

costing (;//) foc$s on the economic performance of waste management systems#

The methos have ifferent foc$s an hence ifferent fiels of applications#

5innveen et al# (200C) provie an overview of the vario$s methos an a

g$ieline for choosing among the ifferent methos, s$ggesting ;/* as

appropriate for comparing environmental impacts from ifferent waste

management options#

3eviews con$cte by e#g# @illan$eva 7 en&el (200C) an /leary (2008)

confirme that ;/* has been a wiely applie tool for assessment of waste

management sol$tions $ring the past 1>!20 years# 6n aition, several moels



have been evelope as s$pport tools for ;/* on waste management systems#

E4amples are G3*3E (Dalemo et al#, 188CQ A.orkl$n, 2000), 3*TE

(Thomas 7 McDo$gall, 200>Q Ientil et al#, 200>) an E*E*TE (9irkeby et

al#, 200+Q /hristensen et al#, 200C)# Gverviews an comparisons of the ifferent

moels are provie in inkler 7 Ailitewski (200C) an Ientil et al# (2008)#

5inally, the $se of life cycle thinking in waste management has been promote in

the E$ropean waste framework irective (Directive 200:8:E/) stating that

eparting from the waste hierarchy, which is otherwise the g$iing principle

behin waste management in EU, may be possible when .$stifie by life cycle

thinking (E$ropean Parliament, 200:)#

1.2.1 Evaluation of waste based energy productionEnergy plays a significant role in waste management systems as energy is neee

to operate the vario$s treatment facilities an often more importantly beca$se

energy can be recovere from waste# To acco$nt the impacts an potential savings

from waste base energy pro$ction, the energy pro$cts an their application

sho$l be aresse separately# Electricity an heat, for e4ample, are pro$ce,

istrib$te an $se ifferently which sho$l be reflecte by the ientification of

the s$bstit$te energy#

* critical factor with respect to eval$ating waste base energy pro$ction is

relate to ientification of the s$bstit$te energy# 6entification of the s$bstit$te

energy in a short!term time perspective can be one base on the c$rrent esign of

the energy system# To moel the impacts of a ecision with long!range

conseF$ences is m$ch more problematic an associate with large $ncertainties as

the f$t$re is inherently $ncertain# Energy system analysis (E*) has within recent

years been $se as a metho for etermining the affecte energy technologies anf$els (e#g# ;.$nggren!oerman, 200aQ ahlin et al#, 200=), b$t also this approach

is associate with $ncertainties as the res$lts of the E* epen on the technical

specifications of the energy system, an the constraints an ass$mptions

employe in the moel#

1." Aim of t#e t#esis

6n orer to provie an improve basis for selecting technologies for energy

pro$ction from waste in Denmark, the overall aim of this thesis was to provie a

systematic framework for ;/* moeling of waste!to!energy technologies an



=

recommenations for preferre technologies# ith a foc$s on ;/* of energy $se

an recovery within waste management, this involve the following more etaile

ob.ectives"

H 6entify critical goal an scope relate factors (s$ch as time perspective, an

scale of the change) with potential significant infl$ences on the o$tcome of

the ;/*

H Eval$ate an s$ggest how these factors sho$l be aresse an F$antifie

in a Danish conte4t

H Eval$ate which contrib$tions are important for the environmental

performance of waste!to!energy technologiesH *ssess how the s$bstit$te energy sho$l be ientifie

H Aase on the items above, ientify the preferre waste!to!energy

technologies in a Danish perspective

The above iss$es were investigate from a Danish perspective with a foc$s on

comb$stible waste (as receive toay at m$nicipal soli waste incinerators in

Denmark)# The waste!to!energy processes incl$e in the thesis were waste

incineration, anaerobic igestion an co!comb$stion as these processes wereconsiere most relevant from a Danish perspective# aste incineration was given

most foc$sQ tho$gh, $e to its significance in the Danish waste management

system# *naerobic igestion is applie as a treatment option for the organic

ho$sehol waste only in some m$nicipalities, b$t the technology may become

more wiesprea in the f$t$re e#g# for co!igesting with man$re which is

consiere a large $n$se energy potential# /o!comb$stion of waste is not yet

$se in Denmark, b$t has been teste in a few cases# everal other waste!to!

energy alternatives e4ist s$ch as gasification, pyrolysis, an pro$ction of

bioethanol or bioiesel (Mnster, 2008)# Bone of these processesQ however, are

likely to be real alternatives to waste incineration within a foreseeable f$t$re#

Iasification an pyrolysis are only s$itable for a limite amo$nt of waste

fractions, an technologies for pro$ction of liF$i biof$els are still in an early

stage of evelopment#



>

5$el s$bstit$tion was moele by creiting the waste management system with

the avoie energy pro$ction in the energy system# The $nerlying ass$mption

behin this approach was that energy pro$ce from waste offsets energy

pro$ce from other f$els, which wo$l otherwise have been $se to f$lfill the

energy eman# The benefits were ascribe the waste management system, as

energy recovere from waste is a conseF$ence of the specific treatment waste is

s$b.ect to in the system#

1.$ %ontent of t#esis

The str$ct$re of the thesis is as follows"

H /hapter 2" Describes ;/* methoology in general an the specific ;/*

methoology applie in the thesis# 6ncl$e impact categories an $nits are

escribe#

H /hapter " Eval$ates an isc$sses factors relate to the goal an scope

efinition to provie a basis for ;/* of waste!to!energy technologies# The

chapter elaborates on some of the topics in 5r$ergaar et al# (6), Mathiesen et

al# (66) an Damgaar et al# (@6)#

H /hapter =" 6entifies which contrib$tions are significant in ;/*s of waste!to!energy technologies# Eval$ates ifferent approaches for ientification of

the s$bstit$te energy, an provies e4amples an res$lts from two case

st$ies# This chapter elaborates on the finings in 5r$ergaar et al# (6),

5r$ergaar et al# (666), 5r$ergaar 7 *str$p (6@) an *str$p et al# (@)#

H /hapter >" Aase on /hapter an = this chapter isc$sses iss$es regare

as most problematic to aress an acco$nt in ;/*#H /hapter +" /oncl$es on the o$tcome of the thesis#

H /hapter C" Disc$sses topics which co$l be f$rther investigate base onthis thesis#



+



C

2&et#od

2.1 '%A wit#in waste managementThis PhD thesis is base on the principles of ;/*# 5$ll ;/*s were con$cte in

5r$ergaar 7 *str$p (6@) an Damgaar et al# (@6)# The remaining fo$r papers

employe life cycle thinking, foc$se on a single ;/* impact category or

isc$sse the metho# ;/* was chosen as metho in this thesis as it is a

stanari&e metho (6G, 200+aQ 200+b) an commonly $se for environmental

eval$ations of waste management systems# ;/* aims at incl$ing an F$antifying

all irect an inirect emissions an reso$rce cons$mptions thro$gho$t the life

cycle of the consiere pro$ct or system, thereby proviing a holistic perspectivefor the eval$ation#

;/* was originally evelope as an environmental assessment metho for

pro$cts, $s$ally referre to as %crale!to!grave' assessments# E4traction of raw

materials for pro$ction of the pro$ct is the %crale' of the assessment, an

isposal of the pro$ct the %grave'# This is ifferent from the life cycle of waste

management systems, where the %crale' is isposal of a pro$ct, i#e# when a

pro$ct enters the waste management system as waste# This is also referre to as

the %&ero b$ren' approach, as all $pstream emissions associate with generating

the waste are omitte from the ;/* (e#g# /lift et al#, 2000)# The %grave' is when

waste leaves the system, either as emissions (from e#g# lanfills) or as energy or

seconary materials, potentially s$bstit$ting pro$ction of energy an virgin

materials in the interlinke systems#

;/*s consist of fo$r phases which accoring to the 6G 1=0=0 stanars are thefollowing" Ioal an scope efinition, inventory analysis, impact assessment an

interpretation (6G, 200+a)# The first phase incl$es specification of the aim of

the ;/* an efinition of system bo$naries an the f$nctional $nit (the $nit

which F$alitatively an F$antitatively escribes the service provie by the

system)# *s calc$lations in the later phases of the ;/* are base on the f$nctional

$nit an this $nit f$rther is the basis for comparison with other alternatives an

scenarios, it is an important parameter# Gften, the f$nctional $nit is efine base



:

on the consiere waste type an waste treatment option# Gther critical aspects

within the first phase of the ;/* are relate to efining the framework of the

assessment with regar to the temporal, technological an geographical scopes,

the ;/* approach applie, etc# These efinitions serve as fo$nation for the

s$bseF$ent phases an sho$l accoringly be thoro$ghly aresse# 6n the secon

phase, all relevant irect an inirect emissions associate with $pstream an

ownstream activities are collecte an presente base on the f$nctional $nit,

followe by the thir phase where the emissions are characteri&e an aggregate

in accorance with the incl$e impact categories# 6n the fo$rth an last phase, the

res$lts of the impact assessment are interprete base on the goal an scope of the

assessment an the inventory analysis#

2.2 Applied '%A met#odology

The environmental impacts were assesse an eval$ate by ED6P8C, a mipoint

;/* methoology evelope by en&el et al# (188C)# The calc$lations were

performe by $se of the ;/* base moel, E*E*TE (9irkeby et al#, 200+)#

The res$lts were normali&e $sing the latest version of the normali&ation

references for ED6P8C (tranorf et al#, 200>)# The impact categories incl$e

were" Ilobal arming (I), *ciification (*/), B$trient Enrichment (BE),

Photochemical G&one 5ormation (PG5), -$man To4icity via air (-Ta), via water

(-Tw) an via soil (-Ts), an Ecoto4icity in ater (chronic) (ETw) an in soil

(ETs)# The first fo$r impact categories are commonly referre to as energy relate

impacts, or non!to4ic impacts, whereas the remaining categories are referre to as

to4ic impacts# here general consens$s e4ists with regar to assessing the energy

relate impacts, the opposite is the case for the to4ic impact categories# ;ack of

inventory ata an lack of consens$s concerning the characteri&ation metho $se

have res$lte in these impacts being consiere less rob$st than the energy relate

impacts (5innveen et al#, 2008)# /onseF$ently, the two impact gro$ps are often

kept separate when ;/* res$lts are presente to emphasi&e that the two gro$ps

are perceive ifferently# *nother possibility is to simply omit the to4ic impact

categories from the ;/*Q however, this may provie misleaing res$lts# *n

e4ample co$l be a comparison of two waste incinerators with ifferent levels of

fl$e gas cleaning, where the incinerator with the most efficient cleaning system



8

$s$ally cons$mes more reso$rces an energy compare with the incinerator with

more simple eF$ipments installe# *n opposite sit$ation is seen for emissions of

to4ic s$bstances where the emission level in the latter case wo$l be larger than in

the first case# Ay only incl$ing energy relate impacts, the o$tcome of the ;/*

wo$l favo$r the incinerator with an inefficient cleaning system thereby not

creiting the efficient incinerator for re$cing the air emissions#

The res$lts from the impact assessments were in this thesis shown either as

characteri&e impact potentials (in kg /G2!eF#) or normali&e impact potentials

(in milli!person eF$ivalents (mPE))# 1 mPE represents one tho$santh of the

ann$al impact from an average person in a given area, i#e# 100 mPE corresponsto 10 of the ann$al impact from an average person#



10



11

"Important goal and scope related factors

The goal an scope efinition forms the fo$nation of any ;/* an is therefore

critical for the res$lts# everal factors relate to the goal an scope efinition neeto be clarifie, tho$gh# Either beca$se these factors are often not aresse in ;/*s

or clear escriptions regaring how the factors have been aresse are omitte# *s

these factors can be consiere critical with regar to eval$ation of waste!to!energy

technologies an in ;/*s in general, the p$rpose of this chapter is to clarify an

elaborate on these factors an provie recommenations for how they sho$l be

aresse# The chapter e4pans on the finings in 5r$ergaar et al# (6), Mathiesen

et al# (66) an Damgaar et al# (@6)#

".1 (oal definition

The goal of an ;/* sho$l state the intene application, the reason for performing

the st$y, the intene a$ience an whether the res$lts are intene for $se in

comparative assertions isclose to the p$blic (6G, 200+a)# 6f the latter is the case,

a critical review of the ;/* sho$l be con$cte# The first two items are often

given most foc$s an they m$st also be consiere as the most critical with respect

to clarifying the p$rpose of the ;/*# *s the remaining phases of the ;/* epenon the efine p$rpose, the p$rpose sho$l be clearly escribe# 6f the aim of the

st$y is to compare recycling of paper with incineration, it sho$l be clarifie

whether the intention is to s$pport the ecisions of a specific m$nicipality or to

s$pport national ecision makers# The process for s$bstit$tion of virgin paper is the

same in both cases, b$t the s$bstit$te heat from waste incineration epens on the

location of the waste incinerator (e#g# 5r$ergaar et al# (666))# *t a m$nicipal level

ata representing a specific istrict heating network sho$l be applie, b$t this is

not feasible at a national level# -ere ata ill$strating the %average' affecte heatsho$l be applie, e#g# a weighte average of heat s$bstit$tion from the

appro4imately 0 waste incinerators in Denmark# The concl$sions may not be the

same in the two cases#

".2 T#e '%A approac#

Two overall ;/* approaches e4ist" attrib$tional an conseF$ential# here foc$s of

the attrib$tional ;/* is on F$antifying the environmental loas of a pro$ct or

system by escribing all environmentally relevant physical flows to an from the



12

ob.ect in foc$s, the aim of the conseF$ential ;/* is to assess the conseF$ences of a

ecision by incl$ing only the potentially affecte physical flows (eiema et al#,

1888)# *verage ata are $se for the attrib$tional approach whereas marginal ata,

ata representing the technologies act$ally affecte by the change, are $se for the

conseF$ential approach# GftenQ however, lack of marginal ata makes it impossible

to perform a 100 conseF$ential ;/* an average ata are often $se to some

e4tent#

*nother factor ifferentiating the two approaches is the metho $se for

istrib$tion of environmental b$rens in the cases of open!loop recycling or m$lti!

o$tp$t or m$lti!inp$t processes" allocation or system e4pansion# Gpen!loop

recycling is conversion of a recycle material into another pro$ct ifferent from

the original, e#g# recycling of polyethylene terephthalate (PET) bottles into

polyester for pro$ction of fleece sweaters# *n e4ample of a m$lti!o$tp$t process is

waste incineration, where the pro$ctsservices provie are waste treatment an

energy pro$ction# *nother e4ample is combine heat an power pro$ction#

Pro$ction of biogas from anaerobic igestion of organic ho$sehol waste an

man$re, an management of resi$al waste (consisting of n$mero$s waste

fractions) are e4amples of m$lti!inp$t processes# *ll types of processes are freF$entin ;/* of waste management systems, which reners consens$s important with

regar to which metho to apply# This is not f$lly the case toay as also isc$sse

by 5innveen et al# (2008)# Bevertheless, $s$ally allocation (partitioning of

environmental b$rens between the pro$cts) is associate with the attrib$tional

approach, whereas system e4pansion (e4paning the system to incl$e s$bstit$tion

of other pro$cts) is associate with the conseF$ential approach# This ivision is

base on the arg$ments that attrib$tional ;/*s o not incl$e $nit processes

o$tsie the life cycle investigate, as oppose to conseF$ential ;/*s which incl$e

all affecte $nit processes inepenent on these being insie or o$tsie the life

cycle (e#g# 3$ssell et al#, 200>)#

The incongr$ence relate to the choice of ;/* approach, the ata types $se an

the metho applie for istrib$tion of environmental loas is ca$se by the fact that

when ;/* was intro$ce no istinction was mae between the two approaches#

Griginally, ;/* was evelope simply as a tool for performing comprehensive

environmental assessments of pro$cts, b$t the nee for a harmoni&ation of the



1

metho res$lte in the 1880Oies in evelopment of a n$mber of g$ielines an

recommenations, e#g# a %/oe of Practice' evelope by ET*/ in 188 (/onsoli

et al#, 188)# The importance of incl$ing market aspects in ;/*s was propose

the same year by eiema (188), an later a istinction was mae between ;/*s

aiming at escribing the conseF$ences of a change rather than ;/*s aiming at

escribing all environmentally relevant physical flows to an from the ob.ect in

foc$s (Aa$mann, 188:)# The terminology $se toay (conseF$ential vers$s

attrib$tional) was formally aopte at a workshop in 2001 (/$rran et al#, 200>), b$t

ifferent terminologies have been $se thro$gho$t the years an are sometimes still

$se# The conseF$ential approach may also be referre to as prospective an

comparative, an the attrib$tional approach as retrospective, escriptive or of the

acco$ntancy type (e#g# eiema, 188:Q Ekvall et al#, 200>)# Toay, ;/* is a

stanari&e methoQ however, the 6G stanars refrain from proviing

recommenations on methoological choices, thereby leaving the choice of ;/*

approach to the ;/* practitioner#

The ;/*s performe in this thesis were base on the conseF$ential approach as

this approach was regare as most s$itable for the p$rpose of the ma.ority of

;/*s" to eval$ate the possible conseF$ences of a ecision# ystem e4pansion anmarginal ata have been $se where possibleQ however, it was not possible to

entirely avoi allocation" in case of energy s$bstit$tion from waste incineration the

environmental loas of the conventional /-P plant ientifie as affecte were

partitione between heat an electricity by means of allocation# Gverall, the

approach may be efine as %pragmatic conseF$ential', an the topics aresse in

the s$bseF$ent chapters of the thesis were base on this approach#

"." Scale of t#e c#ange

Eval$ating the conseF$ences of a change is linke to ientification of the marginaltechnology# The marginal technology has been efine as the technology act$ally

affecte by a small change in eman (e#g# eiema et al#, 1888), an this

efinition originates from economics where the marginal cost is the cost of

pro$cing one more $nit of a goo# 5rom a mathematical perspective the change is

infinitesimal# Using the term marginal therefore implies that the change is

insignificant with respect to the affecte system# 6n ;/*s of waste management



1=

systems where a ecision may involve h$nre tho$sans tonnes of waste, it is

relevant to ask whether the in$ce changes can be efine as marginal#

The answer to this F$estion epens on which systems are affecte by the change#The vol$me of the waste management system is small compare with the

s$rro$ning systems, s$ch as the electricity gri an the market for materials# *lso

a istrict heating network is small in comparison with the electricity gri# *

ecision which have a significant effect of the waste management system, may

therefore only have very limite effect on the market for materials# kovgaar et al#

(200C) s$ggeste that marginal ata are $se for moeling of recycling processes

an most processes o$tsie the waste management system, s$ch as the electricity

system, whereas average ata or ata representing a significant effect are $se for

most of the waste management system# The recommenations for the waste

management system nat$rally epen on the e4pecte effects of the ecision, b$t

most waste management policies will have significant effects within the waste

management system (kovgaar et al#, 200C)# Decisions infl$encing istrict heating

networks will also often be significant as heat recovere from waste contrib$tes

significantly to the istrict heating pro$ction in Denmark, an in some networks

constit$tes the ma.ority of the heat pro$ction#

The abovementione aspects emphasi&e the importance of 1) specifying the

processes an systems possibly affecte by the consiere ecision an 2) efining

how m$ch waste is affecte by the ecision# The latter sho$l be a part of the

f$nctional $nit efinition, as this is a prereF$isite for eval$ating the scale of effects

on the waste management system an, if affecte, the istrict heating network

system# 3egarless of the scale in F$estion, the res$lts of the ;/* may still be

reporte per tonne of waste to ens$re comparability with other st$ies#

5inally, this ill$strates that the recommenation of employing %marginal' ata in

conseF$ential ;/*s is only tr$e for small changesQ however, treatment of h$nre

tho$san tonnes of waste can still be efine as a small change if trae on large

market which is the case for e#g# steel# 6n many casesQ tho$gh, the conseF$ences of

ecisions in waste management will be significant, inicating that instea of $sing

the term %marginal', terms s$ch as %affecte' or %infl$ence' wo$l be more

appropriate# This is in line with eiema (200) who s$ggeste avoiing the term



1>

%marginal' an instea $sing the term %the technology act$ally affecte'# 6n

general, the recommenation for ;/* practitioners is to pay attention to the

$nerlying ass$mptions with regar to the terminology (s$ch as the scale of a

change) an to specify how the terminology has been $se in the specific ;/*# 6n

this thesis, the term %marginal' is $se when referring to effects on electricity

pro$ction, whereas %affecte' is $se for effects on the waste management system

an the istrict heating network#

".$ Time perspecti!e

everal time perspectives sho$l be consiere in ;/*s of waste management

systems#3.4.1 Global warming characterization

Gne time hori&on is relate to global warming, where the impacts can be assesse

over 20 years, 100 years or >00 years# The characteri&ation factor of the vario$s

gasses contrib$ting to global warming epens on how the gas concentration

ecays over time in the atmosphere# * common proce$re is to $se a time hori&on

of 100 years#

3.4.2 Emissions from landfilled waste

*nother time hori&on concerns eval$ation of lanfille waste where only a small

amo$nt of the materials is release within a foreseeable f$t$re# The ma.ority of

materials is store in the lanfills an emissions from lanfills can contin$e for

tho$sans of years# Different approaches e4ist for moeling the impacts of

lanfille waste" from $sing a time hori&on of 100 years or shorter, thereby

acco$nting for only a minor fraction of the emissions, to an infinite time hori&on

incl$ing all emissions# *nother approach is to incl$e a new impact category

referre to as %tore to4icity' (-a$schil et al#, 200:) which acco$nts for the

to4icity of the materials remaining in the lanfill after the efine time perio of

100 years# The o$tcome of the ;/* with respect to to4icity epens heavily on the

time aspects applie renering a clear escription of the approach important#

3.4.3 System lifespan

* thir time hori&on which sho$l be consiere is the lifespan of the system or the

treatment technology in foc$s, e#g# intro$ction of a new collection scheme for

recyclables or constr$ction of a new incineration plant# The lifespan incl$es the



1+

planning phase, the constr$ctionimplementation phase, the $se phase an the

ecommission phase# 6eally, the environmental impacts of all phases e4cept the

planning phase are incl$e an acco$nte for in the ;/*, often however, only the

$se phase is incl$e $e to lack of ata on the remaining phases# The impacts of

the omitte phases are either ass$me insignificant compare with the impacts from

the $se phase, or in case the ;/* compares two systems with similar constr$ction

an ecommission phases the impacts are often ass$me to be of similar si&e

thereby co$nterbalancing each other in the ;/*# The lifespan of a new collection

scheme for recyclables may not be longer than !> years, if the following is

ass$me" planning < implementation" 1 year, trial perio" 2!= years# Depening on

the res$lt of the trial perio the collection scheme may either contin$e or beterminate# The lifespan of a waste incinerator is significantly longer,

appro4imately 2>!0 years base on the following ass$mptions" planning" 2 years,

constr$ction" 2 years, $se" 20!2> years, ecommission" 1 year#

Gften, the f$nctional $nit is efine as treatment of 1 tonne of waste witho$t

consiering the lifespan of the system# The e4pecte lifespanQ however,

significantly infl$ences technology ata, efficiencies, energy s$bstit$tion, etc#

".) Tec#nological scopeThe technological scope is highly relate to the time hori&on an the geographical

scope as technology ata sho$l reflect the time perio as well as the location of the

assessment# D$ring the past years waste!to!energy technologies have been s$b.ect

to a significant improvement with respect to emission control an energy recovery

efficiencies# Damgaar et al# (@6) assesse the evelopment in irect emissions

from waste incinerators by moeling eight scenarios with increasingly effective

fl$e gas cleaning" from no fl$e gas cleaning to very avance air poll$tion control

technology# Time wise, a perio of =0 years was reflecte, from the early 18C0Oies

$ntil toay# The st$y showe a ma.or ecrease in impacts from waste incineration,

especially with respect to the to4ic impact categories which were all re$ce by

several orers of magnit$e# *lso the evelopment in energy recovery efficiencies

was eval$ate in Damgaar et al# (@6) emphasi&ing the significance of recovering

both electricity an heat#



1C

The st$y ill$strate the importance of taking technology evelopment into

consieration when moeling scenarios with longer time hori&ons# 5inally, it

stresses the importance of collecting $p!to!ate technology ata an not blinly $se

ol ata, which is often the sit$ation when $sing ;/* atabases#

".* (eograp#ical scope

The geographical scope is significant as the technological level an the

combination of technologies may iffer from co$ntry to co$ntry# here some

co$ntries are still epenent on ol, inefficient technology other co$ntries $tili&e

new, efficient eF$ipment with a minim$m of environmental impacts# *lso the

effects of energy s$bstit$tion are highly relate to the geographical scope, as thecomposition of energy systems with respect to technologies an f$els vary between

co$ntries# 5r$ergaar et al# (6) reviewe several st$ies foc$sing on the /G2

emission factors employe for electricity pro$ction# The res$lts are seen in 5ig$re

1#



1:

+.$ +.* +.,

lectricity pro!ision -kg %+2e/.0kW#

Figure 1# Ireenho$se gas emissions for electricity pro$ction# The fille bars

incl$e emissions from f$el comb$stion as well as $pstream emissions# The stripe bars only incl$e emissions from f$el comb$stion (5r$ergaar et al#, 6)#

Most ata in 5ig$re 1 represent electricity mi4es, whereas a few represents a single

f$el type# The ata showe variations $p to 1+0 times ill$strating the impacts of

energy s$bstit$tion to be highly co$ntry specific if average ata are $se in the

moeling# *s emphasi&e previo$sly the conseF$ences of energy s$bstit$tion

sho$l be moele by ata representing the act$al change, b$t the st$y of

5r$ergaar et al# (6) showe that also these ata may vary significantly epenenton the technological level# Despite its importance for the res$lts it may be a

iffic$lt task to efine where effects of a ecision will happen# 3ecycle materials

are trae on a global market an electricity is transmitte across national borers#

*lso the time perspective is critical as markets evelop over



18

time# These iss$es sho$lQ nevertheless, be consiere as they may significantly

impact the res$lts#

". %32 emission trading sc#eme 4TS5*nother important aspect with respect to eval$ating the conseF$ences of energy

s$bstit$tion is the effect of the E$ropean /G2 emission traing scheme (ET)

which came into force in 200> (E$ropean Parliament, 200)# The traing scheme

involves aro$n 10000 companies within the energy an in$strial sectors ann$ally

being responsible for appro4imately =0 of the EUOs greenho$se gas emissions#

The scheme establishes an $pper limit (often referre to as a %cap') to the /G2

emissions within the EU from the sectors incl$e in the traing system, as only acertain level of emission permits are available each year# *s an increase in energy

pro$ction (an accoringly /G2 emissions) in one area m$st be met by similar

ecreases in another area the effects of a change in energy pro$ction is being

isc$sse# 5innveen (200:) for e4ample isc$sse whether the marginal electricity

pro$ction in the f$t$re may be regare as /G2!free as any action $ner the cap

is co$nterbalance by another action# This may be tr$e in a short!term perspective,

as /G2 emissions within the c$rrent traing perio (200:2012) are fi4e# *fter this

perio, a new traing perio for 201!2020 will be establishe, where the cap neesto be lowere for EU to obtain its goal of re$cing its /G 2 emissions by 20

before 2020 (compare with the 1880 level)# 6n a long!term perspective, meas$res

affecting energy pro$ction will th$s have an effect on /G2 emissions, as the EU

co$ntries nee to re$ce their energy cons$mption, increase their share of

renewable energy an intro$ce cleaner energy technologies# 6t is therefore

reasonable to ass$me that intro$ction of new waste base energy technologies in a

long!term perspective can contrib$te to f$lfilling these targets#

5or a co$ntry to f$lfill its obligations with respect to re$cing its /G2 emissions it

is allowe to b$y a restricte amo$nts of creits in co$ntries o$tsie EU by

investing in vent$res which re$ce /G2 emissions in these co$ntries (e#g /lean

Development Mechanism (/DM) an oint 6mplementation (6))# 6n principal, this

means that the marginal technology for electricity pro$ction in a long!term

perspective co$l be constit$te by a /DM pro.ect# -owever, whether the marginal



20

energy technology or a /DM pro.ect sho$l be $se epen on act$al f$el prices,

/G2 F$ota prices, etc#

6n general, in a short!term perspective the marginal electricity pro$ction may beregare as essentially /G2!free, whereas this is not the case in a long!term

perspective# Meas$res affecting energy $se an pro$ction will have an effect in a

long!term perspectiveQ however, this may potentially be investments in a /DM

pro.ect#

"., T#e type of effects included

The goal an scope relate factors isc$sse in the previo$s chapters relate to theconsiere system an the assessment approach# *t a ne4t level the type of effects

(short!term or long!term) incl$e nee to be aresse# This chapter acco$nts for

the essential aspects of efining these effects#

3..1 Short!term or long!term effects

The type of effects to incl$e in an ;/* is often regare as irectly linke to the

time hori&on of the st$y# Bevertheless, espite the terms %short!term' an %long!

term' effects, these e4pressions are only inirectly linke to the lifespan of the

investigate system# 6nstea the terms refer to the type of effects to incl$e in a

conseF$ential ;/* (eiema et al#, 1888)# * istinction originating from

economics is mae between ecisions which only affect the e4isting pro$ction

capacity (the short!term effects) an ecisions which are e4pecte to involve

changes in pro$ction capacity (the long!term effects) (eiema et al#, 1888)# 6n a

short!term perspective the pro$ction capacity is consiere fi4e, implying that

the short!term technology is an e4isting technology capable of responing to

changes in eman by a.$sting its o$tp$t# /onensing coal power is often referreto as the marginal short!term technology for electricity in the caninavian

co$ntries $e to the fact that a s$rpl$s of coal capacity e4ists in the Danish gri as

reserve capacity to meet electricity eman in perios with low pro$ction from

win t$rbines# 6n a long!term perspective the pro$ction capacity is consiere

fle4ible, implying that the marginal long!term technology is a new facility b$ilt or

an ol plant ecommissione (eiema et al#, 1888)# The marginal long!term

technology in caninavia may therefore be constr$ction of new win t$rbines or

ecommissioning of ol coal!fire power plants epening on the tren in eman#



21

6t is not a trivial task to ecie which type of effects to incl$e in an ;/* as most

ecisions have both short!term an long!term effects# *nother iss$e complicating

the ecision is relate to the fact that the time perspective of the assessment also

affects the ecision# This comple4ity is ill$strate in Table 1#

Most ;/*s are performe to s$pport ecisions mae toay, which means that it is

most relevant to foc$s on the left sie of the iagram# Th$s, when referring to a

short!term or long!term effect in this thesis, it refers to ecisions mae toay#

The type of effect to incl$e epens to some e4tent on the scale of the change an

the lifespan of the ecision# -owever, the following isc$ssion s$ggests that the

lifespan of the ecision is of minor importance# The e4amples from section #=#

are $se for clarification, as they represent systems with a short an a long lifespan,

respectively# The scale of change is aresse in the following#

6ntro$cing a new collection scheme for recyclables in a m$nicipality wo$l

pres$mably imply more collection (an hence an increase eman for transport

f$els, e#g# iesel)# The benefit wo$l be more recyclables collecte an hence morevirgin materials s$bstit$te (isregaring any market constraints, etc#)# The scale of

change m$st be regare small (the changes occ$r in the f$el s$pply system an at

the market for virgin materials) an the lifespan short (!> years)# This s$ggests that

the e4tra eman for iesel an the re$ce eman for virgin materials possibly

can be met by a.$stments within the e4isting capacity, implying that a short!term

marginal technology is affecte# Bevertheless, even tho$gh the lifespan is too short

for new investments in pro$ction capacity (or ecommissions), intro$ction of a

new collection scheme wo$l likely also have conseF$ences on f$t$re investments#

Table 1# Type of effects to incl$e in conseF$ential ;/*#/$rrent 5$t$re

hort!term ecision mae toay, which only

affects the e4isting pro$ction

capacity

ecision mae in the f$t$re,

which only affects the e4isting

pro$ction capacity;ong!term ecision mae toay, which

involves changes in pro$ction

capacity

ecision mae in the f$t$re,

which involves changes in

pro$ction capacity



22

The market wo$l not %know' that the increasere$ce eman may only be

temporary an wo$l still have to a.$st its pro$ction capacity# 6f the collection

scheme after the trial perio is mae permanent the ecision wo$l affect

investments provie the scale of change is large eno$gh, i#e# the effects referre to

as the long!term marginal effects# 6t co$l also be arg$e that even if the scheme

wo$l only r$n in a short time perio the most correct way of eval$ating the

conseF$ences of its intro$ction wo$l be to consier the possible effects of

increase recycling within a longer time perio than !> years# This isc$ssion

s$ggests that even in cases where the lifespan is short, the act$al conseF$ences will

most likely be far!reaching, an the effects best moele with ata representing

long!term marginal effects#

6n the case of constr$ction of a new incineration plant with a total lifespan of 2>0

years it seems more evient that this will at some point affect investments in the

energy system# 6n the first years of the incineratorOs $se phase, the e4isting

pro$ction capacity nees to a.$st (i#e# leaing to short!term marginal effects), b$t

hereafter investments are affecte# The intro$ction of new incineration capacity

will have a significant effect on the istrict heating network an a minor effect on

the electricity system# To eval$ate the effects on the istrict heating network thelocation of the waste incinerator sho$l be taken into consieration as local

conitions are critical for the environmental performance# This is elaborate in

5r$ergaar et al# (666) an f$rther isc$sse in /hapter =#=# The effects on the

electricity system are best moele with ata representing longterm marginal

effects#

*s aforementione is any ecision e4pecte to ca$se both short!term an longterm

effects# The main impactsQ however, are the effects on investment ecisions (e#g# toecommission an ol coal!fire power plant) as well as avoie $tili&ation of the

ecommissione plant (e#g# avoie comb$stion of coal)# 6eally, both types of

effects sho$l be incl$e in an ;/*Q however, in most cases the short!term effects

are negligible compare with the long!term effects# This is $e to long!term effects

being more permanent, as the short!term effects will only last $ntil the ne4t

capacity change (eiema, 200)# 5or simplicity, it is therefore recommene to

foc$s on ientifying the long!term effects#



2

3..2 "dentifying the long!term effects

The technologies consiere as the possible long!term technology (marginal or

affecte) may be constraine, which means that their pro$ction capacity cannot be

e4pane# This may be $e to nat$ral constraints, political constraints, or marketconstraints for co!pro$cts (eiema et al#, 1888)# *n e4ample is constraints on

hyropower in some co$ntries where it is not allowe to e4pan the areas $se for

hyropower generation# *nother e4ample is emission limits an F$otas which may

constrain the $se of highly poll$ting technologies# Use of biomass for energy

pro$ction is also e4pecte to be constraine in the f$t$re $e to ins$fficient

availability of lan for both energy crops an crops for foo an foer# -owever,

the 6nternational Energy *gency estimates that energy pro$ction from biomass

co$l be fo$r to five times o$ble witho$t risking the worlOs f$t$re foo s$pply

(6E* Aioenergy, 200C)# This s$ggests that biomass will not be constraine the ne4t

many yearsQ however, this may epen on regional conitions# in is often

mentione as constraine as its pro$ction cannot be a.$ste to the emanQ

however, this is only tr$e for the short!term effects# *s constraints may change over

time, $e to e#g# changes in political ob.ectives, it may lea to false concl$sions to

e4cl$e a technology $e to c$rrent constraints# /onseF$ently, it is recommene

to regar all technologies as options, or at least thoro$ghly investigate theconitions before e4cl$ing a given technology#

*lso the tren in eman is importantQ however, as this will affect whether a

ecision will impact the planning of new technology or phasing o$t of ol

technology# To $se the market for electricity as an e4ample" if the overall eman

for electricity is increasing (or ecreasing at a slower rate than the average

replacement rate of ol technology) new pro$ction capacity m$st be installe to

meet the eman (eiema, 200)# This will $s$ally be the most preferre option,s$ch as moern, competitive technology# 6f the overall eman for electricity is

ecreasing (at a faster rate than the average replacement rate) pro$ction capacity

will be ecommissione# This will $s$ally be the least preferre option at the

market, e#g# an ol poll$ting technology#

The conseF$ences of a ecision either in$ce a ecrease or an increase in eman#

6ncrease energy recovery from waste re$ces the eman for conventional f$els



2=

an vice versa# 6entifying the long!term marginal effects of a ecision sho$l be

relate to the general tren of the marke# This is ill$strate in Table 2#

Table 2 s$ggests the tren in eman rather than the conseF$ence of a ecision to

be ecisive for ientification of the long!term marginal technology# 6f the market

for electricity is increasing, a re$ce eman for electricity will have the effect

that investments in new plant capacity is postpone, whereas an increase eman

res$lt in investments being initiate# 6n both cases, the ata $se in the moeling

sho$l represent energy pro$ction at the most preferre technology# 6f the market

for electricity is ecreasing, on the other han, a re$ce eman res$lts inecommissioning of ol plants, whereas an increase eman most likely res$lt in

the life of ol plants being prolonge# *gain, ata $se for moeling the

conseF$ences sho$l be alike an ill$strating energy pro$ction at the least

preferre plants#

Pro.ections can be $se for efining the tren in emanQ however, the tren in

eman is affecte by vario$s factors s$ch as economy, political ob.ectives, etc,

an may accoringly be iffic$lt to efine# The tren in eman may also be

consiere constant, s$ggesting that the conseF$ence of a ecision may be to

prolong the life of an ol plant as oppose to investing in a new# /onseF$ently, the

long!term marginal technology may shift back an forth between vario$s

technologies#

6t sho$l be emphasi&e that the isc$ssions above only apply to changes which

can be consiere small compare to the overall market, e#g# electricity# 6ntro$cing

Table %$ cheme for ientification of the long!term marginal technology#/onseF$ence of ecision in waste system

6ncrease eman Decrease eman

T r e n i n m a r k e t

e m a n

6ncreasing 6nvestments in new plants

initiate

6nvestments in new plants not

initiatepostponeDecreasing *voie ecommissioning of

ol plantsProlonging the life

of (ol) e4isting plants

Decommissioning of ol

plants



2>

a new incineration plant (or implementing a ecision of a similar si&e) will have a

significant effect on a istrict heating network an the effects sho$l be eval$ate

case!by!case# This recommenation is in line with eiema (200) who

isting$ishe between small an large effects#

6entifying the f$t$re affecte plants is associate with large $ncertainties as the

f$t$re is inherently $ncertain# This was isc$sse in Mathiesen et al# (66) where an

assessment of the historical evelopment of the Danish energy system was

performe thro$gh reviews of several p$blications# The p$blications were a mi4 of

official energy plans, energy plans from BIGs an statistical ata showing what

act$ally happene# Discrepancies between what wo$l have been ientifie as the

long!term marginal technology for electricity by $sing the plans an which

technology was act$ally intro$cephase o$t were fo$n in several cases# @ario$s

ca$ses were ientifie for the iscrepancies" technological evelopment being

isregare, wrong price preiction of e#g# f$els an /G2 F$otas, an a shift in

ob.ectives in the time perio consiere# *s a variety of technologies co$l

potentially by ientifie as the long!term marginal technology Mathiesen et al# (66)

recommene to $se several significantly ifferent technologies in the ;/* to test

the importance of electricity# 6f energy was critical for the res$lts it was s$ggesteto perform energy system analysis of ifferent f$t$re scenarios# -owever, for most

;/* practitioners it is too time cons$ming to perform an energy system analysis in

aition to the ;/*, an it sho$l also be acknowlege that the o$tcome of an

energy system analysis heavily epens on the constraints an ass$mptions applie

in the moel# Gn the other han, energy system analysis can be $sef$l as a tool for

showing the possible conseF$ences of ifferent actions, an can as s$ch be $se

more generally for ientifying possible important interactions in the energy system#

6n /hapter >#1 res$lts from an energy system analysis is $se to show how thelong!term marginal electricity pro$ction co$l be ientifie#

Aase on abovementione finings it is recommene to test the rob$stness of the

;/* by applying two significantly ifferent long!term marginal technologies for

electricity pro$ction# Possible technologies are isc$sse in /hapter > where also

specific recommenations for heat are provie#



$'%A of wastetoenergy tec#nologies

This chapter o$tlines e4amples of energy flows to an from the waste management

system, an acco$nts for significant contrib$tions in ;/*s of waste!to!energytechnologies in a systems perspective# Energy s$bstit$tion, for e4ample, contrib$tes

significantly to impacts on global warming, whereas other contrib$tions are

significant for the to4ic impact categories# 6n contin$ation of the finings in

/hapter , ifferent approaches with respect to ientifying the s$bstit$te energy

are acco$nte for# 5inally, the chapter gives concrete e4amples of 1) ientification

of the s$bstit$te energy in two ifferent istrict heating networks an 2) ;/* of

waste!to!energy technologies# This chapter elaborates on finings in 5r$ergaar et

al# (6), 5r$ergaar et al# (666), 5r$ergaar 7 *str$p (6@) an *str$p et al# (@)#

$.1 nergy flows

The waste management system an the energy system are closely interlinke, an

the interactions between the two systems nee to be aresse caref$lly to eval$ate

the effects of energy recovery from waste in a consistent an transparent manner#

The waste management system nees energy to operate the ifferent treatment

processes, b$t the waste!to!energy technologies also generate ifferent o$tp$tsintene for $se in ifferent parts of the energy system# The inp$ts an o$tp$ts are

ill$strate in 5ig$re 2# E4amples of energy pro$cts from the system are electricity,

heat an f$els s$ch as biogas, lanfill gas, soli recovere f$el (35) an vario$s

biof$els# The f$els may have several applications an can be $tili&e for pro$ction

of heat an electricity as well as $tili&e in the transportation sector as f$els for

vehicles# The characteristics of the vario$s o$tp$ts an calorific val$es of the f$els

are escribe in more etails in 5r$ergaar et al# (6)#

Wastelectricity

6 7

8eat %ollection Anaerobic digestion

9uels . Transportation %omposting

Diesel: Pretreatment S;9 production <

;ecycling =iofuel production>atural gas

T#ermal treatment 'andfilling3il

(asoline



$.2 Important contributions

To acco$nt for all environmental impacts relate to the $se of a given waste!to!

energy technology all irect as well as inirect contrib$tions sho$l be incl$e in

the assessment# Direct contrib$tions are irectly linke to the activities within the

waste management system, whereas inirect contrib$tions occ$r o$tsie the system#

The inirect contrib$tions can be ivie into two categories" $pstream activities

s$ch as pro$ction of materials an energy $se insie the system, an ownstream

activities encompassing s$bstit$tion of materials an energy recovere within the

system an management of resi$es generate in the system# These iss$es aref$rther elaborate on with regar to greenho$se gases in 5r$ergaar et al# (6) an

*str$p et al# (@)#

The significance of a contrib$tion with respect to the o$tcome of an ;/* epens

on the impact categories incl$e an the framework of the assessment# 6f global

warming is the only impact category incl$e the impacts of leaching from e#g#

bottom ashes become insignificant for the res$lts# Ilobal warming is tho$gh a

highly relevant impact category with respect to eval$ation of energy aspects, b$t as

emphasi&e by Merril (2008) a relatively poor inicator for the overall

environmental performance of a waste management system# 6n the following

sections, the significance of vario$s contrib$tions with respect to eval$ating the

environmental performance of waste incineration, co!comb$stion an anaerobic

igestion is aresse# * istinction was mae between contrib$tions to global

warming an contrib$tions to other impact categories#

*lectricity

8eat 9uels

=iogas S;9

=iofuels

'andfill gas

Figure %$ E4amples of energy flows to an from the waste management system

(5r$ergaar et al#, 6)#



4.2.1 #ontributions to global warming

The inirect ownstream contrib$tions with respect to global warming have in

many st$ies (e#g# ;.$nggren!oerman, 200bQ 5innveen et al#, 200>) been

ientifie as the ownstream contrib$tions ca$se by energy recovery, i#e# avoiegreenho$se gas emissions $e to energy s$bstit$tion# The savings from energy

s$bstit$tion off!set in most cases the loa from irect an inirect $pstream

contrib$tions, res$lting in net savings of global warming# The magnit$e of savings

epensQ however, on the type of energy pro$cts generate (only electricity, only

heat or a combination of both), on the f$el types s$bstit$te, energy recovery

efficiencies an the fossil carbon content of the waste# 5or anaerobic igestion of

organic waste the fossil carbon content is approaching &ero an emissions of /G2

are th$s irrelevant for the res$lts# 6nstea, f$gitive emissions of methane from the

anaerobic igestion plant an from comb$stion of the biogas become important for

the o$tcome# *lso the final estination of biogas is significant, i#e# whether $tili&e

for heat an power pro$ction or $tili&e in the transportation sector (5r$ergaar 7

*str$p, 6@)#

*str$p et al# (@) teste the importance of the aforementione contrib$tions for

waste incineration of mi4e ho$sehol waste an co!comb$stion of soli recoveref$els (35), a high calorific waste, in a coal!fire power plant# Energy recovery

efficiencies ill$strating low respectively high performance base on Danish

conitions were employe in the assessment# *lso two ifferent types of /G2

emission factors for electricity pro$ction were employe" a low val$e representing

an energy system with a high share of renewable energy an a high val$e

representing a system preominantly base on coal# aste incineration res$lte in

net global warming savings, also in the case of low energy recovery efficiencies

combine with a low /G2 emission factor for electricity# The savings were then preominantly ca$se by heat s$bstit$tion# /o!comb$stion, on the contrary,

res$lte in net global warming loas in the case of low energy recovery combine

with a low /G2 emission factor# This was ca$se by the high fossil carbon content

of 35, being twice as high as the fossil carbon content of the mi4e waste inp$t

for waste incineration# *lso the m$ch lower heat recovery efficiencies at the co!

comb$stion plant infl$ence the res$lts# -owever, in cases with a high egree of

energy recovery combine with employment of a high /G2 emission factor, co!



comb$stion co$l potentially save $p to twice as many /G2! eF#tonne of wet waste

(ww) incinerate compare with incineration" a net saving of appro4imately 1>00

kg /G2!eF#tonne 35 (ww) $e to co!comb$stion vers$s :00 kg /G 2!eF#tonne

mi4e waste (ww) $e to incineration# This confirms the significance of ientifying

the esign of the interacting energy system with respect to technologies an f$els#

*str$p et al# (@) also fo$n that the inirect $pstream emissions were primarily

relate to electricity cons$mption at the plants, an that presorting of the waste for

35 pro$ction constit$te aro$n >0!:0 % of the $pstream emissions for co!

comb$stion#

4.2.2 #ontributions to other impact categories

The other impact categories incl$e in this PhD thesis are *ciification (*/),

B$trient Enrichment (BE), Photochemical G&one 5ormation (PG5), -$man

To4icity via air (-Ta), via water (-Tw) an via soil (-Ts), an Ecoto4icity in

ater (chronic) (ETw) an in soil (ETs)# -ow m$ch these vario$s impact categories

are infl$ence epens on the waste fraction treate (an hence the chemical

composition of the waste), the waste!to!energy technology an the ass$mptions

mae with regars to treatment of the resi$es#

5r$ergaar 7 *str$p (6@) incl$e two types of waste fractions (35 an organic

ho$sehol waste) an three ifferent waste!to!energy alternatives (waste

incineration, co!comb$stion in a coal!fire power plant an anaerobic igestion) in

an ;/* encompassing the abovementione impact categories# aste incineration

with or witho$t energy recovery was $se as reference technology for both waste

fractions, whereas co!comb$stion was employe for 35 only an anaerobic

igestion employe for the organic ho$sehol waste#

Treatment of 35 affecte especially -Tw an -Ts (an I)# Energy s$bstit$tion

ca$se net I savings for waste incineration as well as cocomb$stion, whereas

only waste incineration yiele net savings with respect to -Tw an -Ts# /o!

comb$stion ca$se a net loa in these two impact categories, mainly $e to less

efficient fl$e gas cleaning at the co!comb$stion facility compare with the waste

incinerator# The impacts were mainly ca$se by emissions of -g# Different impact

categories were affecte when organic ho$sehol waste was consiere, an as it



was the case for 35 it was cr$cial for the res$lts whether the organic waste was

treate by incineration or anaerobic igestion# Aoth waste incineration an

anaerobic igestion affecte I, b$t especially BE, ETw an -Tw were

infl$ence by the choices mae with respect to management of igestate from the

anaerobic igestion process# The igestate was ass$me $tili&e as fertili&er at

Danish farmlan which both create savings (in ETw) $e to s$bstit$tion of

inorganic fertili&er b$t also loas (BE an -Tw)# The BE loas were a conseF$ence

of an increase r$n!off of nitrate to s$rface water, whereas heavy metals in the

igestate ca$se the -Tw loas#

To s$m $p, especially irect an inirect ownstream emissions were fo$n to be

significant for the res$lts# 5or treatment of 35, especially cleaning of the fl$e

gases was a critical factor, whereas the res$lts for treatment of organic ho$sehol

waste were highly affecte by the ass$mptions mae with regar to hanling of the

igestate#

$." Approac#es for modeling of energy reco!ery

*s escribe in the previo$s chapters the s$bstit$te energy has large impacts on

the res$lts, which emphasi&es the importance of ientifying the real conseF$encesof energy pro$ction from waste# everal st$ies have been performe $ring the

past ecaes foc$sing on energy recovery from waste, an these st$ies were

e4amine to eval$ate how they aresse the goal an scope relate factors

elaborate on in /hapter # 5oc$s was on the choice of ;/* approach an the type

of effects incl$e as these iss$es $s$ally are the most iffic$lt to aress properly#

* range of st$ies foc$sing more specifically on heat s$bstit$tion were also

eval$ate#

4.3.1 $pproaches in literature% energy recovery in &#$

* vast range of ;/* st$ies have been performe $ring the past years, an several

of these st$ies foc$se on or incl$e energy recovery from waste# B$mero$s

st$ies foc$se on waste incineration as an inivi$al technology (;iamsang$an 7

Iheewala, 200CQ 3iber et al#, 200:Q Morselli et al#, 200:Q ;$oranen et al#, 2008Q

Moora 7 ;ahtvee, 2008), or as part of a national waste system, in some cases also

isc$ssing other options s$ch as recycling an lanfilling (e#g# ;.$nggren!

oerman, 200bQ Eriksson et al#, 200>Q 5innveen et al#, 200>Q A.orkl$n 7



5innveen, 200CQ Eriksson et al#, 200C)# ome st$ies have eval$ate anaerobic

igestion (e#g# Aor.esson 7 Aergl$n, 200+Q 200C), an a few st$ies have

compare several technologies with a eicate foc$s on energy pro$ction (e#g#

/onsonni et al#, 200>aQbQ *&apagic, 200C)#

The ma.ority of st$ies i not e4plain which ;/* approach was applie, b$t

average ata were applie in most of them# ystem e4pansion in terms of

s$btracting avoie energy pro$ction $e to energy recovery was performe in all

st$ies, b$t only aro$n half of the st$ies arg$e for their choice of s$bstit$te

energy# Gne st$y i not even mention which type of f$els was ass$me

s$bstit$te# *ppro4imately one thir of the st$ies foc$se on eval$ating the long!

term effects, whereas the remaining st$ies eval$ate the short!term effects# ;ess

than half of the st$ies performe a sensitivity analysis of the conseF$ences of

s$bstit$ting another type of f$el than the original# 6n the st$ies performing a

sensitivity analysis it was fo$n that the choice of f$el $se in the ;/* ha large

impact on the res$lts, e#g# by changing the ranking of scenarios#

$mming $p, the ma.ority of st$ies wo$l benefit from a sensitivity analysis of

the s$bstit$te f$el type to eval$ate the rob$stness of the res$lts# The same is tr$ewith respect to o$tlining the scope of the ;/* which is a prereF$isite for

$nerstaning an eval$ating the res$lts in the right conte4t# The finings clearly

inicate the necessity of proviing a systematic framework for eval$ating of waste!

to!energy technologies, an in general to enhance the creibility of several of the

st$ies#

4.3.2 $pproaches in literature% heat substitution

6n the st$ies above foc$s was especially on the waste management system or onsingle waste technologies an the f$els ientifie as s$bstit$te were base on

literat$re or general ass$mptions# * range of st$ies (not necessarily ;/*s) have

eval$ate the interactions between the waste management system an the energy

system more thoro$ghly, either by $se of energy system analysis or by combining

ifferent moels# 6n the ma.ority of st$ies, the aim has been to eval$ate the

conseF$ences of heat recovery from waste incineration when $tili&e for istrict

heating p$rposes# Glofsson (2001) linke a waste management moel with a moel

for a istrict heating system on a case st$y of two m$nicipalities# ;.$nggren!



oerman (200a) calc$late the marginal heat pro$ction costs of available

pro$ction alternatives, an s$bseF$ently applie the ientifie f$els in ifferent

scenarios for the st$ie waste management system# ahlin et al# (200=), -olmgren

7 Iebremehin (200=) an 9n$tsson et al# (200+) eval$ate M incineration

from an energy systems perspective $sing economic optimi&ation moels

sim$lating the istrict heating network system# The st$ies were con$cte as

either local or national s$rveys# *n e4ample of a local s$rvey was fo$n in

-olmgren 7 Iebremehin (200=) foc$sing on a single m$nicipality# ;.$nggren!

oerman (200a) on the other han applie a national approach an moelle the

conseF$ences of M incineration base on the average weish istrict heating

network# ahlin et al# (200=) an 9n$tsson et al# (200+) also applie a national

approach, b$t base on a moel aggregating n$mero$s local istrict heating

networks into one large system, representing 88 of the weish istrict heating

pro$ction#

The st$ies above were performe with ifferent aims an perspectives, an all of

them foc$se on weish conitions# 6t was therefore not possibly to $se the res$lts

as inp$t to ;/*s of heat s$bstit$tion in a Danish perspective# 5irst of all beca$se

several of the st$ies foc$se on costs which m$st be e4pecte to iffer fromDanish conitions, where a large share of the heat is base on fossil f$els as

oppose to ween where biomass covers a significant share# econly, beca$se

the Danish energy system contrary to the weish system is heavily base on

combine heat an power pro$ction# Thirly, beca$se the esign of istrict heating

networks iffers significantly renering local conitions important when

F$antifying the environmental conseF$ences of energy recovery# *s a conseF$ence

a case st$y was performe aiming at eval$ating the importance of local conitions

for waste incineration with energy recovery in a Danish perspective# The st$yfoc$se on important esign an operational properties of the other heat pro$cing

facilities in the network to which the waste incinerator was attache#

$.$ %ase study? district #eating networks

6n Denmark, a s$bstantial share of the electricity an heat pro$ction is cogenerate

(see Table )#



6n 200C, aro$n >0 of the electricity pro$ce at /-P plants were pro$ce in

combination with heat, corresponing to aro$n =0 of the total electricity

pro$ction# *ro$n :0 of the total heat pro$ction was generate in combination

with electricity (DE*, 200:)# /onseF$ently, in ;/*s involving energy s$bstit$tion

in Denmark this co!pro$ction sho$l be acco$nte for#

The Danish istrict heating network system in one of E$ropeOs most e4pane

consisting of more than =00 self!containe networks of vario$s si&e an esign#This necessitates a local approach in cases where heat s$bstit$tion is cr$cial for the

res$lts, e#g# when ientifying a proper location for a new waste incinerator, or

eval$ating whether permissions sho$l be given with regar to increasing the

capacity of e4isting waste incinerators# 5r$ergaar et al# (666) investigate the

conseF$ences of waste base heat s$bstit$tion in two specific Danish istrict

heating networks by acco$nting for the energy!associate interactions between the

plants connecte to these networks# The st$y foc$se on energy an /G2 an 10

I of f$el (corresponing to appro4imately 1 tonne of waste) was $se as basis for

the calc$lations# * short!term time perspective was applie as the aim was to

provie an $nerstaning of the mechanisms in the istrict heating network rather

than to preict the long!term effects#

The two networks (referre to as /ase 1 an /ase 2) were s$pplie with heat from

vario$s facilities, b$t each network was ominate by two plants" a waste

incinerator an a large /-P plant# The /-P plant in /ase 1 was a large conensing

Table )$ Danish electricity an heat pro$ction in 200C (after DE*, 200:)#Electricity -eat

P P /entral /-P plants :8#> += >=#> =>

H separate electricity

pro$ction at central plants

H >=#1 ! ! !

Decentrali&e /-P plants 1C#0 12 2+#: 22-eat!only boilers ! ! 1C#C 1>Private /-P pro$cers :#= + 1+#2 1

Private heat!only boilers ! ! +#= >in t$rbines 2>#: 1: ! !

Total 1=0#C 100 121#+ 100



cogeneration plant mainly f$elle by coal, whereas the plant in /ase 2 was a back!

press$re plant mainly f$elle by woo chips, nat$ral gas an oil# The relationship

between heat (*R) an electricity pro$ction (*P) at these two plants was

characteri&e by the following eF$ations"

*P S ! /v *R (/ase 1" EF$ation 1)

*P S /m *R (/ase 2" EF$ation 2)

/v S %the power!loss ratio', $s$ally aro$n 0#1>!0#20 for Danish plants/m S %the power!to!heat ratio', ranges between 0#= to 1 or more epenent on

the technology#

The eF$ations were $se to calc$late the conseF$ences of e4tra waste base heat

s$pplie to the istrict heating system# The technical esign of the /-P plant in

/ase 1 allowe for a fle4ible pro$ction of heat an electricity, an eF$ation 1 was

$se to calc$late how m$ch e4tra electricity the plant co$l pro$ce when the

eman for heat was re$ce# The technical esign of the /-P plant in /ase 2, on

the other han, impose a fi4e ratio between heat an electricity, as these types of

plants can only generate electricity when a eman for heat e4ists# EF$ation 2 was

$se to calc$late the re$ce electricity pro$ction# 5ig$re ill$strates how the

effects of increase waste incineration in terms of heat an electricity s$bstit$tion

were moele with /ase 2 as e4ample#

+.++)@,2+.B,@,2

"ncinerationplant

lectricity lectricity produced

at marginal %8P plant

4coal5

8eat

8eat produced

at #eatonly boiler 4natural gas5

8eat produced

at #eatonly boiler

8eat produced

at 8erning %8P plant4wood c#ipsC natural gas oil5

lectricity produced

at 8erning %8P plantwood c#ipsC natural gas oil5



Figure )$ -eat an electricity s$bstit$tion in /ase 2 (5r$ergaar et al#, 666)#

The waste base electricity was ass$me to s$bstit$te coal conensing electricity at

the gri (terme marginal electricity in 5ig$re ), whereas waste base heat was

sen to the istrict heating network s$bstit$ting mainly heat pro$ction at the large

/-P plant# This was base on the ass$mption that heat from waste incineration

(acting as base loa in the istrict heating system) mainly s$bstit$tes other base

loa technologies# -owever, the analysis of the yearly heat pro$ction in /ase 2

showe that reservepeak loa boilers in some months constit$te a significant

share of the total heat pro$ction, inicating that increase waste incineration mayalso infl$ence these plants# This was acco$nte for in the moeling by incl$ing

also heat s$bstit$tion at two ifferent heat!only boilers# The conseF$ences of

re$ce heat pro$ction at the large /-P plant are ill$strate by ashe lines in

5ig$re # The electricity pro$ction at the /-P plant is re$ce accoring to the /m

val$e, an to maintain a constant electricity pro$ction in the system the %missing'

electricity m$st be pro$ce at another plant, here ass$me to be the marginal /-P

plant#

4.4.1 'esults

The energy an /G2 acco$nts ill$strate that it is ins$fficient to foc$s solely on

plant efficiencies when eval$ating the environmental performance of waste

incinerators# More energy was s$bstit$te in /ase 1 espite the efficiency of the

waste incinerator in /ase 2 being slightly higher# The smaller energy saving in



/ase 2 was ca$se by the eman for e4tra electricity to compensate for the

missing electricity when re$cing the pro$ction at the /-P plant in /ase 2# *

more prono$nce ifference was seen with respect to /G2 emissions" where waste

incineration in /ase 1 yiele a saving of =: kg /G2I inp$t to the incinerator, it

provie a loa of = kg /G2I inp$t in /ase 2# This correspone to a saving of

appro4imately =:0 kg /G2 an a loa of =0 kg /G2, respectively, per tonne of

waste incinerate# This ifference was ca$se by the f$els $se in the networks# 6n

/ase 1, primarily coal base energy was s$bstit$te, whereas the s$bstit$te energy

in /ase 2 was comprise by biomass, nat$ral gas an oil# The savings at the /-P

plant in /ase 2 were too low to co$nterbalance the loa from the coal base

electricity neee to compensate for the missing electricity in the system#

6n concl$sion, the istrict heating network, the interactions with the electricity

system an the affecte f$els showe to be cr$cial for the o$tcome# *itionally,

the res$lts s$ggest not locating new incineration capacity in a network ominate

by back!press$re plants if the compensatory electricity wo$l be base on fossil

f$els#

$.) %ase study? '%A of wastetoenergytec#nologies

6n the st$y of 5r$ergaar 7 *str$p (6@) referre to in section =#2#2, ;/*s of three

waste!to!energy technologies (mass b$rn incineration, co!comb$stion in coal!fire

power plant an anaerobic igestion) were con$cte to eval$ate the environmental

impacts of energy pro$ction from two types of m$nicipal soli waste" 35 an

organic ho$sehol waste# The moele alternatives are o$tline in Table =#

To test the significance of the f$els ientifie as s$bstit$te energy s$bstit$tionswere consiere with respect to two ifferent energy systems" a present!ay system

base on fossil f$els an a f$t$re system base on 100 renewable energy# 6n a

present!ay perspective, the following f$els were ass$me s$bstit$te"

H aste incineration with energy recovery" mainly coal

H /o!comb$stion in coal!fire power plant" mainly coal



H *naerobic igestion, biogas $se for /-P" mainly nat$ral gas, b$t also

biomass an coal

H *naerobic igestion, biogas $se for transportation" petrol

The f$els ientifie as s$bstit$te in a present!ay perspective were partly base on

an energy system analysis of the Danish energy system (Mnster, 2008)# 6n

moeling of a f$t$re system, electricity an heat was ass$me to be pro$ce

e4cl$sively from biomass, whereas liF$i transport f$els were ass$me to be

bioiesel#

4.(.1 'esults

5ig$re = shows the res$lts of the ;/* with respect to energy pro$ction from 1

tonne of organic ho$sehol waste in a present!ay perspective# 5or the ma.ority of

impact categories, incineration with energy recovery prove to be a better

alternative than anaerobic igestion regarless whether the pro$ce biogas was

$tili&e for /-P pro$ction or as transport f$el# ith respect to I, the higher

energy conversion rate of the waste incinerator compare with the rate of the

anaerobic igestion plant was significant for the o$tcome# *lso the f$el typess$bstit$te were significant, tho$gh#

Table /$ aste!to!energy technologies assesse# %4' inicates the alternatives

moele for the two waste fractions#35 Grganic waste

aste incineration witho$t energy recovery 4 4

aste incineration with energy recovery 4 4

/o!comb$stion in coal!fire power plant 4

*naerobic igestion# Aiogas for /-P pro$ction# 4

*naerobic igestion# Aiogas as transportation f$el# 4



Figure /$ Environmental impacts from treatment of 1

tonne of organic ho$sehol waste in a present!ay

perspective# The graphs incl$e res$lts base on the

original ass$mptions (referre to as 3E5) as well as

res$lts from the sensitivity analysis (referre to as EB)#

EB=" coal s$bstit$tion instea of the mi4 of nat$ral gas,

biomass an coal s$bstit$tion#



* sensitivity analysis (referre to as EB= in 5ig$re =) was con$cte

eval$ating the effects of s$bstit$ting coal instea of the mi4 of nat$ral gas,

biomass an coal when biogas was $tili&e for /-P pro$ction# This improve

the environmental performance of anaerobic igestion within some impact

categoriesQ however, waste incineration with energy recovery was still s$perior in

the ma.ority of categories# ith respect to $tili&ation of biogas, $se as transport

f$el prove to be slightly better than /-P pro$ction# 6n a f$t$re perspectiveQ

however, these small ifferences were evene o$t#

The res$lts of the ;/* concerning energy pro$ction from 35 showe co!

comb$stion to have benefits over waste incineration with energy recovery with

respect to the non!to4icity impact categories, whereas the opposite was the case

with respect to the to4ic impacts# Aoth alternatives ca$se environmental savings

with respect to the non!to4ic impacts, whereas this was only the case for waste

incineration when consiering the to4ic impacts# *s mentione in section =#2#2

co!comb$stion generate significant loas primarily ca$se by air emission of -g,

highlighting the importance of efficient fl$e gas cleaning systems at cocomb$stion

facilities# 6n the moeling of waste incineration not all the generate heat was

ass$me $tili&e to ill$strate the reality for many waste incinerators# -owever, asit wo$l not make sense to increase incineration capacity in an area where the

pro$ce heat co$l not be $tili&e a sensitivity analysis was performe to

eval$ate the conseF$ences of 100 heat $tili&ation# Iiven all the pro$ce heat

co$l be $tili&e the two alternatives wo$l be comparable with respect to the

non!to4ic impact categories#

*s aforementione the assessment was also performe with an energy system

base 100 on biomass to moel to conseF$ences of the changes that mayhappen in the f$t$re as the energy system is e4pecte to change from a system

primarily base on fossil f$els to a system more base on renewable energy# The

moeling of the waste!to!energy technologies $sing two ifferent energy systems

as reference showe that the overall ranking of the technologies was not

significantly affecte by the choice of f$els in the system# This s$ggests that the

res$lts of the assessment are rob$st also in the f$t$re# -owever, with respect to



I all alternatives contrib$te with loas as oppose to the savings obtaine in

the present!ay energy system base on fossil f$els#



=2



=

) Discussion

This chapter isc$sses the iss$es fo$n to be associate with the largest

$ncertainties relate to energy s$bstit$tion" ientification of the long!termmarginal technology an f$el for electricity pro$ction an ientification of the

long!term effects of heat s$bstit$tion# Aase on these isc$ssions the res$lts of the

two case st$ies are eval$ate an recommenations for treatment of comb$stible

waste in a Danish conte4t are provie#

).1 'ongterm marginal electricity production

The long!term marginal technology an f$el for electricity pro$ction epen on

the tren in eman, b$t is also affecte by political consierations as escribe in

section #:#2# This chapter isc$sses possible alternatives for ientification of the

long!term marginal technology an f$el, an provies vario$s s$ggestions in this

regar#

3ecommenations with respect to ientifying the long!term marginal energy

technology an f$el epen on the geographical scope of the ;/*# Electricity is

istrib$te via large, interconnecte gris across national borers, anientification of the long!term marginal technology for electricity sho$l therefore

be base on the e4pecte evelopment of the gri in the concerne area# 5or

Denmark (an the other caninavian co$ntries) this involves evelopment in the

Boric gri, which is also connecte to Iermany, Polan, -ollan, Estonia an

3$ssia# *s these connections are ass$me to become stronger in the f$t$re it is

relevant to foc$s on the entire Aaltic ea 3egion when eval$ating the f$t$re# *

pro.ection of the evelopment in this region co$l be $se to ientify the longterm

marginal electricity# *n e4ample of s$ch a pro.ection was evelope for the Boric /o$ncil of Ministers an the Aaltic Development 5or$m (E*

Energianalyse, 2008)# The pro.ection foc$se on ientifying how the electricity

sector in the Aaltic ea 3egion co$l evelop $ntil 200 while complying with the

EU targets for 2020 (renewable energy constit$ting 20 an a /G2 re$ction of

20 ) an a target of >0 % /G2 re$ction in 200 (compare with 1880)# The

energy system analysis moels tream an Aalmorel were $se#



==

The analyses showe an increasing tren in electricity pro$ction an that

investments wo$l be mae primarily in new efficient coal!fire power plants an

win power# * few investments wo$l be mae in new biogas plants, b$t these

investments were small compare with investments in coal an win technologies#

This s$ggests the long!term marginal technology for electricity co$l be

constit$te by two f$namentally ifferent technologies" coal an win power#

* ifferent way of ientifying the long!term marginal technology an f$el wo$l

be by ass$ming a target of achieving environmental s$stainability as the

$nerlying basis for the isc$ssion# 5oc$sing on EU, s$ch a target is linke to the

overall goal of sec$rity of s$pply# To achieve this goal the EU /ommission has propose ifferent meas$res, among others to improve cross!borer

infrastr$ct$res an to improve the energy efficiency in especially b$ilings an

in$stry (E$ropean /ommission, 200:)# The vision for 20>0 is to become

inepenent of fossil f$els an re$ce the epenency of f$el import# This is

anticipate to involve a re$ce energy eman, intro$ction of electric cars an

new technologies (e#g# f$el cells), e4pane $se of /-P, an a more intelligent

energy system than the c$rrent capable of a.$sting pro$ction to the act$al

eman an vice versa# * re$ce energy eman wo$l rener the long!termmarginal technology the least preferre technology (se section #:#2)# This wo$l

most likely be technologies $sing fossil f$els (e#g# ol, inefficient coal!fire power

plants or oil technologies)#

The abovementione approaches for etermining the marginal technology are both

$ncertain, b$t both of them s$ggest coal as a possible long!term marginal f$el for

electricity# -owever, the coal technologies are not ientical in the ifferent

e4amples# 6n the e4ample where pro.ections were mae for the Aaltic ea 3egion,

new, efficient plants wo$l be affecte while in the e4ample base on political

visions, ol plants wo$l be affecte# The ifference in electricity conversion

efficiency may be significant# 6n real life, the political framework, f$el prices, /G 2

F$ota prices, etc# may likely affect ecommissioning rates of ol plants an

investments in new plants# 6n any caseQ however, coal comb$stion is a likely long!

term marginal technology#



=>

*s it is not possible to concl$e which approach will yiel the most correct res$lt,

it is recommene to base the ;/* moeling on two significantly ifferent long!

term marginal technologies" coal an win power# To acco$nt for the fact that the

technologies for coal $tili&ation can be very ifferent, it is recommene to either

$se two ifferent ata sets or to $se ata representing a mei$m efficient coal!

fire power plant#

).2 'ongterm effects of #eat substitution

5r$ergaar et al# (666) foc$se on eval$ating the importance of local conitions for

waste incineration with energy recovery" as the aim was to provie an

$nerstaning of the effects of interactions between the waste management systeman the e4isting energy system only the short!term marginal effects were assesse#

This was consiere reasonable for that specific p$rposeQ however, as arg$e in

the previo$s chapters the conseF$ences of a ecision sho$l also acco$nt for the

long!term effects# 5r$ergaar et al# (666) $se 10 I of energy inp$t

(corresponing to appro4imately 1 tonne of waste) as basis for the calc$lations,

b$t in reality a ecision may involve several tho$san tonnes of waste# *ccoring

to the efinitions in /hapter # an the recommenation in section #:#2, this

co$l significantly affect the istrict heating network an sho$l therefore bemoele with ata reflecting these effects# To ientify the act$al effects one co$l

ask" which f$els wo$l have been $tili&e if waste was not available ahlin et al#

(200=) aresse this iss$e an fo$n the answer for ween to be biomass# 6f

waste was not available, the eman for istrict heating wo$l most likely have

been met by investments in facilities $sing biomass#

hether a similar sit$ation wo$l apply also for Denmark is $nclear# *ccoring to

the statistics of the weish District -eating *ssociation biomass constit$te

aro$n 0 of the f$els $se for istrict heating in ween (D-*, 200=)# The

similar fig$re for Denmark was 1+ (DE*, 200:)# The large availability of

biomass $e to large forest areas in ween is a main reason for the c$rrent

ifference between ween an Denmark, b$t this may not be case in the f$t$re#

Denmark is accoring to the EU irective on promotion of renewable energy

oblige to increase the share of renewable energy to 0 in 2020 (E$ropean

Parliament, 2008)# This reF$ires a significant increase in the $se of win power



=+

an biomass# Toay, biomass in the Danish energy system is constit$te mainly by

woo, straw an the bioegraable part of waste, b$t in the f$t$re biogas

pro$ce from man$re is e4pecte to increase# This inicates that if waste was not

available for energy pro$ction more investments wo$l have to be mae in

facilities $tili&ing biomass# in power cannot realistically be consiere the only

sol$tion for increasing the renewable energy share with the c$rrent esign of the

energy system an the nees for a stable electricity s$pply# The sit$ation wo$l

then be similar to the one in ween an biomass wo$l be the affecte f$el# This

concl$sion may be tr$e for an average sit$ation, consiering the more than =00

self!containe istrict heating networks as one interconnecte system# -owever,

for the inivi$al istrict heating networks the sit$ation may still be very ifferent#;/* moeling involving specific networks sho$l incl$e eval$ation of

inivi$al investment plans in orer to properly acco$nt for local conitions#

6n the isc$ssion above the conseF$ences of waste not being available for heat

pro$ction were eval$ate for an average sit$ation# Different sit$ations are

isc$sse in the following#

1# 6ntro$cing waste incineration in a newly establishe resiential area witho$talternative heating facilities"

hich f$els wo$l have been $tili&e in this case if waste was not available *s

previo$sly isc$sse, the answer co$l be biomass# 6t mayQ however, also be

nat$ral gas, since gas is generally consiere a relatively clean f$el an Denmark

has rather e4pane nat$ral gas istrib$tion networks# 6nvestments in coal an oil

technology are $nlikely, as Denmark nees to re$ce /G2 emissions significantly

to meet the political re$ction targets (accoring to the Danish Energy *gency,

Denmark has a /G2 eficit of :!1 million tonnes of /G2 per year for the perio

200:!2012)#

2# 6ntro$cing waste incineration in an area where the heat eman is s$pplie by

a coal!fire /-P plant

6f the eman for heat is constant, the coal!fire /-P plant will have to ecrease

its pro$ction, as waste is a cheaper f$el than coal# This is a short!term effect,

tho$gh# 6f the eman for heat is increasing in the area (an the coal plant cannot



=C

s$pply the e4tra heat) this eman wo$l possibly have been met by investments

in facilities $tili&ing biomass or perhaps nat$ral gas as isc$sse above# This

investment wo$l be avoie by intro$cing waste incineration# 6f the eman for

heat is ecreasing, intro$ction of waste incineration will re$ce the nee for coal

at a faster rate than if waste incineration was not intro$ce# This co$l event$ally

lea to ecommissioning of the coal!fire /-P plant# 5inally, heat pro$ction at

the /-P plant is linke to its electricity pro$ction# 6f electricity prices are high

the /-P plant may still choose to pro$ce electricity an instea cool off the e4tra

heat# 6n this case, the benefits of waste incineration are significantly re$ce# This

m$stQ however, be regare as a short!term effect#

The conseF$ences of intro$cing waste incineration in this sit$ation epen

heavily on the framework conitions# Aiomass an nat$ral gas are e4pecte to be

affecte if the eman for heat is increasing, whereas coal is e4pecte to be

affecte if the eman for heat is ecreasing#

# 6ntro$cing waste incineration in an area where the heat eman is s$pplie by

a nat$ral gas!fire or an oil!fire /-P plant

The conseF$ences will be similar to the conseF$ences in sit$ation 2, b$t withs$bstit$tion of nat$ral gas or oil instea of coal#

$mming $p, the o$tcome epens on the framework conitions# 6ncreasing the

capacity of waste incineration is e4pecte to affect investments in biomass (or

nat$ral gas) technology when the eman for heat is increasing# 6f the eman for

heat is ecreasing, this is e4pecte to affect the e4isting plants (e#g# coal, nat$ral

gas, an oil)#

The isc$ssion above shows that a range of f$els may be affecte by increase

waste incineration# 6n the f$t$re, even more technologies s$ch as solar heat, heat

p$mps an geothermal heat are e4pecte to replace fossil f$els, bringing even

more technologies into play# Al$rring the res$lts even more is the isc$ssion

whether biomass sho$l be consiere constraine or not# 6f not, it is reasonable

to ass$me that waste incineration will s$bstit$te biomass when this f$el type is

e4pecte to be affecte# 6f biomass is consiere a constraine reso$rceQ however,

it will most likely be $se for energy pro$ction in another area, possibly



=:

s$bstit$ting fossil f$els there# *s s$ch biomass cannot be consiere an affecte

f$el#

6f no knowlege is available abo$t the specific istrict heating network an the

evelopment in the area, it is recommene to $se two ifferent types of f$els in

the ;/*# Aiomass sho$l (for now) be $se in one scenario, an nat$ral gas, oil

or coal in the other scenario# -owever, it is recommene that as m$ch

information as possible is gaine with respect to local conitions for assessing

whether coal rather than oil or nat$ral gas to be affecte#

)." !aluation of pre!ious results

The isc$ssions in the two previo$s chapters emonstrate the $ncertainties

relate to ientifying the long!term marginal technology for electricity as well as

the long!term effects of heat s$bstit$tion# The F$estion is how these

recommenations provie above relate to the concl$sions from the st$ies

o$tline in /hapter =#= (5r$ergaar et al# (666)) an /hapter =#> (5r$ergaar 7

*str$p (6@))#

(.3.1 Energy substitution

6n the st$y investigating the conseF$ences of waste base heat s$bstit$tion in two

specific istrict heating networks (/hapter =#=) the short!term effects were

assesse, i#e# changes affecting the e4isting pro$ction capacity# 6f changes

affecting investments were consiere not only the f$el types b$t also the

technologies (an th$s the ratio between heat an electricity pro$ction) co$l be

ifferent# The recommenations from above are in the following only isc$sse

with respect to the affecte f$el type# The same is the case for the st$y o$tline

in /hapter =#>#

P$re coal pro$ction was ass$me affecte in /ase 1 an a mi4t$re of biomass,

nat$ral gas an oil in /ase 2 when heat pro$ction from waste incineration was

increase# The benefits of heat s$bstit$tion in /ase 1 wo$l be significantly

re$ce if biomass instea of coal was ass$me s$bstit$te# The effects wo$l be

smaller for /ase 2 $e to the mi4 of f$els alreay employe in moeling# ;arger

savings wo$l be obtaine if only oil was ass$me affecte, whereas the opposite

wo$l be the case if solely biomass was affecte# The res$lts of the two cases



=8

were highly affecte by the interactions with the electricity system, an for /ase 2

in partic$lar the interactions were critical# -eat s$bstit$tion in /ase 2 ca$se an

e4tra eman for electricity originally ca$sing an environmental loa with respect

to /G2 emissions as the marginal electricity was ass$me to be base on coal# 6f

this electricity pro$ction was base on win, the ifference between the two

cases wo$l ecrease# The ranking of the two cases is therefore e4pecte to be

highly affecte by the choice of marginal electricity# This is in line with the

original concl$sions where an eval$ation of ifferent scenarios for electricity

s$bstit$tion showe to have significant effects on the res$lts# The original

concl$sions concerning the importance of the istrict heating network, the

interactions with the electricity system an the type of affecte f$els wo$lQhowever, not be altere#

6n the st$y reporte in /hapter =#>, ;/*s of ifferent waste!to!energy

technologies were con$cte# -eat s$bstit$tion from waste incineration was in

this st$y moele similar to heat s$bstit$tion in /ase 1 in the previo$s st$y

acknowleging the fact that waste as a reso$rce is $tili&e best in s$ch an area#

The ;/*s were con$cte with s$bstit$tion of fossil f$els as well as renewable

f$els which were in line with the recommenations from /hapter >#2# The res$ltswith respect to ranking of the scenarios were shown to be rob$st towars changes

in the s$bstit$te f$els#

(.3.2 )inal recommendations

The fact that the res$lts were rob$st with respect to changes in the s$bstit$te

f$els ill$strates other contrib$tions besies energy s$bstit$tion to be significant for

the res$lts# These contrib$tions relate as isc$sse in section =#2#2 to the

technologies (e#g# emissions of heavy metals contrib$ting to the to4ic impactcategories), the composition of the waste an in the case of anaerobic igestion to

the ass$mptions concerning management of igestate# This ill$strates the

importance of balancing the time an reso$rces spent on etermining the

s$bstit$te energy technology relative to the time spent on ientifying an

F$antifying other significant contrib$tions#

5inally, it sho$l be consiere whether the finings above allow for

recommenations of a specific waste!to!energy technology in Denmark# *n

answer to this epens to some e4tent on how ifferent impacts are weighte# 6f



>0

recirc$lation of n$trients is important, anaerobic igestion of the organic

ho$sehol waste sho$l be the preferre sol$tion# 6f foc$s instea is on efficient

energy recovery, waste incineration an co!comb$stion of (s$itable) waste

fractions sho$l be preferre# The finings in 5r$ergaar 7 *str$p (6@) inicate

that waste incineration (in comparison with co!comb$stion an anaerobic

igestion) yiels the best res$lts in most impact categories provie all of the

pro$ce heat can be $tili&e#



* %onclusions

To eval$ate the environmental conseF$ences of energy recovery from waste, the

interactions with the energy system have to be acco$nte for as these may have profo$n effects on the res$lts# This also applies for the iss$es relate to efining

the framework of the assessment, i#e# efinition of the goal an scope#

The following goal an scope relate factors were ientifie as critical to ens$re

transparency an consistency in ;/* st$ies" 1) goal efinition, 2) the ;/*

approach, ) the scale of the change, =) the time perspective, >) the technological

an +) the geographical scope, an C) the effects of the /G 2 emission traing

scheme# *lso the type of effects (short!term or long!term) incl$e in the ;/*

was ientifie as critical for the o$tcome# Each of these factors was eval$ate

base on e4amples or general isc$ssions an recommenations provie

regaring how they sho$l be aresse an F$antifie in a Danish conte4t# *s an

e4ample, it was recommene applying the conseF$ential ;/* approach, as the

p$rpose of an ;/* of waste management sol$tions in the ma.ority of cases wo$l

be to eval$ate the conseF$ences of a ecision#

Aase on specific st$ies, it was eval$ate which contrib$tions were important for

the environmental performance of waste!to!energy technologies# *ltho$gh the

significance of the technologies an f$els ientifie as affecte was inisp$table,

especially for global warming, other contrib$tions were significant as well# The

to4ic impact categories were in general more affecte by irect emissions ca$se

by the chemical composition of the waste rather than the s$bstit$te energy# The

impacts from anaerobic igestion of organic ho$sehol waste were strongly

relate to ass$mptions concerning the final estination an $se of the igestate#

The type of energy inentifie as s$bstit$te was fo$n to be highly relate to the

type of effects incl$e in the ;/* an the interactions between the waste

management system an the energy system# 6t was recommene to foc$s on the

long!term effects, i#e# ecisions affecting investments in pro$ction capacity, as

these effects were ientifie as most representative for moeling of changes in the

waste system# This recommenation may give rise to increase $ncertainty in the



;/*Q however, systematic arg$ments for selecting the affecte technologies will

re$ce this $ncertainty an at the same time provie val$able insights in system

interactions an s$bstit$tion mechanisms# ell fo$ne arg$ments are a

prereF$isite for choosing one technology over anotherQ nevertheless, as f$t$re

effects are associate with s$bstantial $ncertainties, it was recommene to test

the importance of energy s$bstit$tion for the ;/* res$lts by $sing two

significantly ifferent technologies# Aase on two ifferent approaches, it was

arg$e that investments in both coal an win technology co$l potentially be

affecte $e to changes in electricity pro$ction# 5or heat pro$ction, investments

in biomass an coal technology (or another type of fossil f$el) co$l potentially be

affecte# The technologies an f$els ientifie as affecte with respect to heat pro$ction wereQ however, highly relate to local conitions#

The significance of interactions between the waste management system an the

energy system was assesse in a case st$y with two specific istrict heating

networks# The high level of /-P pro$ction in the Danish energy system was

fo$n to be cr$cial for the environmental performance of incineration plants, as

re$ce heat pro$ction at the /-P plant also affecte electricity pro$ction# The

effects on electricity pro$ction were relate to the esign of the /-P plant, aslowering heat pro$ction as some plants also res$lts in re$ce electricity

pro$ction# /onseF$ently, the type of plants as well as affecte f$el types sho$l

be aresse when eval$ating the environmental impacts of heat s$bstit$tion#

3ecommenations for treatment of comb$stible waste in Denmark epene to

some e4tent on the foc$s of the assessment an how the vario$s impacts were

weighte# *naerobic igestion of organic ho$sehol waste was the preferre

sol$tion, if recirc$lation of n$trients were consiere important# 6f energy

recovery was prioriti&e, waste incineration was the preferre sol$tion# Provie

all heat co$l be $tili&e, waste incineration with energy recovery prove to be the

best alternative in the ma.ority of impact categories, s$ggesting waste incineration

as a rob$st sol$tion for treatment of comb$stible waste#



9uture work

The work incl$e in this thesis provies a basis for contin$e investigation

within the following topics"

H Eval$ation of new an emerging waste!to!energy technologies# 5oc$s of this

thesis was especially on waste incineration, anaerobic igestion an co!

comb$stion as these technologies were consiere most relevant from a

Danish perspective# 6n the f$t$reQ however, new an emerging technologies

(e#g# for pro$ction of liF$i biof$els) may be relevant for treatment of some

parts of the waste# The ata available for eval$ating these technologies are

often poor as the technologies are still $ner evelopment emphasi&ing the

importance of establishing inventory ata for these technologies#

H 5le4ibility of waste!to!energy technologies# aste incinerators act as base

loa technologies in the energy system as the possibilities of storing waste

over longer perios of time are limite# To increase the share of win in the

energy system the remaining technologies nee to be capable of acting

fle4ibly to ens$re sec$rity of s$pply# ome of the emerging waste!to!energy

technologies have this ability (potentially), e#g# as m$lti!o$tp$t processesgenerating either /-P or liF$i f$els epening on the nee of the system#

The impacts of this ability nee to be incl$e an aresse as waste

incineration otherwise ten to be s$perior in most ;/*s $e its high energy

recovery efficiency#

H The chemical composition of waste# 5or some of the impact categories the

chemical composition of waste is critical, e#g# when eval$ating co!

comb$stion of waste where the air poll$tion control system is less efficient

than at incineration plants# *lso the fossil carbon content is significant with

respect to global warming# To enhance the general rob$stness of the res$lts

more foc$s sho$l be allocate to improving these ata#



>=



>>

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+=



+>

B Appendices

6 5r$ergaar, T#, Ekvall, T# 7 *str$p, T# (2008)" Energy $se an recovery in

waste management an implications for acco$nting of greenho$se gases an

global warming contrib$tions# aste Management 7 3esearch, 2C, C2=!CC#

66 Mathiesen, A#@#, Mnster, M# 7 5r$ergaar, T# (2008)" Uncertainties relate to

the ientification of the marginal energy technology in conseF$ential life cycle

assessments# o$rnal of /leaner Pro$ction, 1C, 11!1:#

666 5r$ergaar, T#, /hristensen, T#-# 7 *str$p, T# (2008)" Energy recovery from

waste incineration" *ssessing the importance of istrict heating networks#

($bmitte to aste Management)#

6@ 5r$ergaar, T# 7 *str$p, T# (2010)" Gptimal $tili&ation of waste to energy in

an ;/* perspective# ($bmitte to aste Management)#

@ *str$p, T#, Moller, # 7 5r$ergaar, T# (2008)" 6ncineration an cocomb$stion

of waste" acco$nting of greenho$se gases an global warming contrib$tions#aste Management 7 3esearch, 2C, C:8!C88#

@6 Damgaar, *#, 3iber, /#, 5r$ergaar, T#, -$lgaar, T# 7 /hristensen, T#-#

(2010)" ;ife!cycle!assessment of the historical evelopment of air poll$tion

control an energy recovery in waste incineration# (Man$script)#

The papers are not incl$e in this www!version b$t can be obtaine from thelibrary at DTU Environment# /ontact info" ;ibrary, Department of

Environmental Engineering, Technical University of Denmark, Mil.oeve.,

A$iling 11, D9!2:00 9gs# ;yngby, Denmark or library?env#t$#k #





T#e Department of n!ironmental ngineering 4DTE n!ironment5 conducts

sciencebased engineering researc# wit#in four t#emes?

Water ;esource ngineeringC Erban Water ngineeringC

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Environmentally Sustainable Utilization of Waste Resources for Energy Production

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