Science of the Total Environment

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 19

Greenhouse gas accounting of the proposed land1047297ll extension and

advanced incineration facility for municipal solid waste management in Hong Kong

KS Woon Irene MC Lo

Department of Civil and Environmental Engineering The Hong Kong University of Science and Technology Hong Kong China

H I G H L I G H T S

bull AIF is better than LFE with regard to

GHG emissions in Hong Kong

bull Major individualsub-processes of LFEandAIF for GHG emissions are investigated

bull GHG emissions for LFE and AIF are

strongly dependent on studied paramet-

ric sensitivity analyses

bull Findings are valuable for sustainable

MSW management and GHG reductions

in waste sector

G R A P H I C A L A B S T R A C T

a b s t r a c ta r t i c l e i n f o

Article history

Received 25 October 2012

Received in revised form 20 April 2013

Accepted 21 April 2013

Available online 19 May 2013

Editor Simon Pollard

Keywords

Municipal solid waste

Greenhouse gas emissions

Land1047297ll

IncinerationPolicy making

The burgeoning of municipal solid waste (MSW) disposal issue and climate change have drawn massive

attention from people On the one hand Hong Kong is facing a controversial debate over the implementation

of proposed land1047297ll extension (LFE) and advanced incineration facility (AIF) to curb the MSW disposal issue

On the other hand the Hong Kong Special Administrative Region Government is taking concerted efforts to

reduce the carbon intensity in this region This paper discusses the greenhouse gas (GHG) emissions from

four proposed waste disposal scenarios covering the proposed LFE and AIF within a de1047297ned system bound-

ary On the basis of the data collected assumptions made and system boundary de 1047297ned in this study the

results indicate that AIF releases less GHG emissionsthan LFEThe GHG emissionsfrom LFE are highly contrib-

uted by the land1047297ll methane (CH4) emissions but offset by biogenic carbon storage while the GHG emissions

from AIF are mostly due to the stack discharge system but offset by the energy recovery system Furthermore

parametric sensitivity analyses show that GHG emissions are strongly dependent on the land1047297ll CH4

recovery

rate types of electricity displaced by energy recovery systems and the heating value of MSW altering the

order of preferred waste disposal scenarios This evaluation provides valuable insights into the applicability

of a policy framework for MSW management practices in reducing GHG emissions

copy 2013 Elsevier BV All rights reserved

Science of the Total Environment 458ndash460 (2013) 499ndash507

Abbreviations AIF advanced incineration facility BAU Business As Usual CLP China Light amp Power DOC degradable organic carbon EIA environmental impact assessment

HKEPD Hong Kong Environmental Protection Department HKSAR Hong Kong Special Administrative Region GDP gross domestic product GHG greenhouse gas GWP Global

Warming Potential IETS Island East Transfer Station IPCC Intergovernmental Panel on Climate Change IWMF Integrated Waste Management Facility IWTS Island West Transfer

Station LFE land1047297ll extension LFG land1047297ll gas LPG Lique1047297ed Petroleum Gas MSW municipal solid waste NENT North East New Territories NLTS North Lantau Transfer Station

OITF Outlying Islands Transfer Facilities RTS refuse transfer station SENT South East New Territories WENT West New Territories WKTS West Kowloon Transfer Station

Corresponding author Tel +852 23587157 fax + 852 23581534

E-mail address cemclousthk (IMC Lo)

0048-9697$ ndash see front matter copy 2013 Elsevier BV All rights reserved

httpdxdoiorg101016jscitotenv201304061

Contents lists available at SciVerse ScienceDirect

Science of the Total Environment

j o u r n a l h o m e p a g e w w w e l s e v i e r c o m l o c a t e s c i t o t e n v

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 29

1 Introduction

With the growth of population urbanization and af 1047298uence dis-

posal of municipal solid waste (MSW) has become a major environ-

mental challenge af 1047298icting people throughout the world (Bogner

et al 2007 UNEP 2009) Hong Kong as a world-class metropolis

is also inevitably faced with this pervasive issue The Hong Kong

Environmental Protection Department (HKEPD) has listed waste

reduction and management policies as an intractable environmentalissue to be resolved (HKEPD 2010a) At present Hong Kong relies

solely on land1047297lls for MSW disposal Approximately 9000 tonnes of

unrecoverable MSWare still discardedin theland1047297llsevery day albeit

Hong Kong has achieved a recycling rate of 52 in 2010 ( HKEPD

2010b) Hong Kong is experiencing a serious shortage of MSW dispos-

al sites with an anticipation that the current three strategic land1047297lls

namelySouth East NewTerritories (SENT) North East New Territories

(NENT) and West NewTerritories (WENT) will be exhausted in 2014

2016 and 2018 respectively (HKEB 2011) In response to this acute

problem there is a pressing need for the HKEPD to identify a compre-

hensive solution A policy framework for the management of MSW

was introduced by the HKEPD in late 2005 to address this problem

One of the approaches applied in this policy framework is bulk reduc-

tion and disposal in which the HKEPD has proposed to implement

land1047297ll extension (LFE) and Integrated Waste Management Facility

(IWMF) with theadvanced incinerationfacility (AIF) as thecore tech-

nology in this IWMF (HKEPD 2005) The implementation of LFE

and AIF however has triggered a strong dispute from stakeholders

such as Hong Kongs citizens and green groups (Ng 2011 2012

Tang 2011) It spurs an intense debate as to whether these waste dis-

posal facilities are truly suitable and sustainable to the Hong Kong

MSW management practices Perhaps it could not be told merely

based on the general perceptions and good experiences of the public

and executive authorities

Apart from this issue the inconvenient truth about the unprece-

dented challenge of climate change has created observable changes

in various weather patterns and drawn extensive concerns from the

public climate panels and policy makers (IPCC 2007 Schiermeier

2011) The waste management sector accounted for approximately3ndash5 of total anthropogenic greenhouse gas (GHG) emissions at a

global scale in 2005 (UNEP 2010) The maximum minimum and

annual average shares of GHG emissions from the waste sector in

Hong Kong from 1990 to 2006 were 59 32 and 45 respectively

which was the third largest sector after electricity generation and

transportation (HKEPD 2010c) Hong Kong as a responsible interna-

tional community always takes initiative to reduce GHG emissions

and combat climate change These initiatives include using cleaner

fuel and renewable energy for power generation promoting energy

ef 1047297ciency and carbon audits in buildings and using energy-ef 1047297cient

transport and cleaner vehicles in the city In 2003 the Kyoto Protocol

was extended to Hong Kong where Hong Kong is attached to main-

land China (de1047297ned as non-Annex 1 Party) and assists the Central

Peoples Government in ful1047297lling the obligations under the KyotoProtocol (HKBEC 2012) While mainland China announced a target

of cutting carbon intensity which is de1047297ned as total mass of carbon

dioxide equivalent emissions per gross domestic product (GDP) by

40ndash45 by2020from the 2005level(Lo2010) theHong Kong Special

Administrative Region (HKSAR) Government has set a more aggres-

sive target to reduce carbon intensity by 50ndash60 by 2020 from the

2005 level for its own region (HKEB 2010) Besides enhancing energy

ef 1047297ciency and revamping the fuel mix for electricity generation

one should take action with the waste sector as there is plenty of

room for GHG emission reductions by employing cleaner waste man-

agement practices or converting waste to wealth through displaced

energy from fossil fuels (Bogner et al 2007) The accounting of GHG

emissions on various MSW disposal methods provides a conceptual

framework with which to describe a carbon footprint concept to the

public and policy makers for understanding the issues surrounding

the need to reduce GHG emissions (Hammond 2007)

The association of MSW disposal issue and GHG abatement

arouses a challenge that how to manage the MSW effectively without

adversely impacting the environment Several studies have recently

been conducted to examine the GHG emissions from land1047297lls and

incineration facilities particularly focused in European and North

American regions (Mohareba et al 2008 Christensen et al 2009

Kaplan et al 2009 Morris 2010 Vergara et al 2011 Assamoi andLawryshyn 2012 Monni 2012) Morris (2010) reported that the

multi-criteria complexity of the land1047297lls and incineration facilities

(eg performance factors waste characteristics and methodology

issues) affected local preferred waste technology decisions The

results are dif 1047297cult to generalize and represent the local environmen-

tal conditions Also most studies did not investigate the GHG emis-

sions from the individual sub-processes of land1047297ll and incineration

Despite the intense debates among the Hong Kong people over the

implementation of LFE and AIF to date a holistic and locally

relevant analysis of the uncertainties of waste-related emissions and

their relationships to GHG emissions of the two proposed LFE and

AIF is yet to be conducted The purpose of this paper is to provide a

comprehensive analysis of GHG emissions for Hong Kongs MSW

that includes different waste disposal scenarios combining proposed

LFE and AIF within a de1047297ned system boundary Only LFE and AIF

are considered in this paper as these two waste disposal facilities

remain the most common disposal methods of MSW disposal in

developed countries (Hoornweg and Bhada-Tata 2012) The results

of this study may serve as an additional view for the development

of practical guidelines in the Hong Kong MSW management system

as well as for investigation of the potential of a policy framework

for MSW management practices in GHG mitigation While most of

the data in this study is locally relevant to the Hong Kong region

the modeling approach applied here may be applicable to other coun-

tries or regions It is hoped that this study will act as a reference

for other places that face a MSW disposal dilemma similar to Hong

Kongs environmental conditions and community needs

2 Material and methods

21 Modeling scope of study

Four scenarios are presented in a summary table as shown in

Table 1 Scenario 1 represents the Business As Usual (BAU) case

(the current practice in Hong Kong) while Scenario 2 serves as a rep-

resentation for the proposed policy framework 2005ndash2014 by the

HKEPD (HKEPD 2005) This scenario consists of the proposal of an

AIF with capacity of 3000 tonnes of MSW per day and the remaining

unrecoverable MSW which is 6000 tonnes per day will be disposed

of at LFE The proposal of the AIF aims to substantially reduce the

bulk size of MSW in hope to minimize the land1047297lling of waste signif-

icantly thereby extending the useable life of current and future land-

1047297lls in Hong Kong This study is extended to Scenario 3 and Scenario 4to investigate the GHG emissions of future action plans that could be

adopted by the HKSAR Government The functional unit used in this

study is based on one tonne of MSW (wet basis) shipped from refuse

transfer station (RTS) to respective waste disposal facilities The indi-

vidual sub-processes which encompass GHG emissions or reductions

in LFE consist of (a) transport of MSW from RTS to LFE (b) land1047297ll

CH4 emissions (c) electricity and heat displaced by energy recovery

system and (d) biogenic carbon storage As for AIF the major pro-

cesses included in this study consist of (a) transport of MSW from

RTS to AIF and ash from AIF to LFE (b) carbon dioxide (CO 2) emis-

sions from stack discharge system due to MSW combustion process

and (c) electricity displaced by energy recovery system The super-

structure of the interrelations among RTS LFE and AIF used in this

study are depicted in Fig 1 Information and data on the physical

500 KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 39

and chemical composition of MSW used in this study are illustrated

in Table 2 The same physical and chemical composition of MSW is

applied to all scenarios to provide a fair comparison The operational

period for LFE and AIF is set to be 10 years in accordance to WENT

and NENT land1047297ll extension environmental impact assessment (EIA)

reports (HKEPD 2007 2009) In this paper the WENT land1047297ll exten-

sion is chosen as a subject of study as it receives the highest rate of

MSW disposal as compared to the other land1047297lls It is assumed that

the GHG emissions produced from the construction of capital and

operating equipment are insigni1047297cant and not included in this study

(Kaplan et al 2009 Morris 2010)

22 Modeling details for LFE

On the basis of the GHG emissions and offset estimates for each

individual process the general equation for calculating the net GHG

emissions from LFE is shown in Eq (1)

GHGLFE frac14 GHGLFETrans thorn GHGLFGminus

GHGLFEGenminus

GHGBCS eth1THORN

where GHGLFE = net GHG emissions from LFE GHGLFETrans = GHG

emissions from MSW transport for LFE GHGLFG = GHG emissions

from land1047297ll CH4 GHGLFEGen = GHG reductions from heat and elec-

tricity generated due to energy recovery system and GHGBCS = GHG

reductions from biogenic carbon storage

221 GHG emissions from MSW transport

The distance traveled is modeled based on the average distance

among 1047297ve RTSs (ie Island East Transfer Station (IETS) Island West

Transfer Station (IWTS) West Kowloon Transfer Station (WKTS)

Outlying Islands Transfer Facilities (OITF) and North Lantau TransferStation (NLTS)) to WENT land1047297ll at Nim Wan (HKEPD 2009) The

MSW transport distance is assumed to be 70 km (round trip) This

assumes that only one trip per day for MSW hauling from each RTS

to LFE The GHG emission factor which accounts for MSW hauling is

equivalent to 191 g CO2e tonneminus1 kmminus1 (container shipping vessel

with 70 average loading) (DEFRA 2011)

222 GHG emissions from land 1047297ll CH 4Since Hong Kong hasnot developedits ownmethod for calculating

CH4 emissions from land1047297ll the estimation of CH4 emissions is

modeled using 2006 IPCC guidelines which employ First Order Decay

method (IPCC 2006) Local data is used whenever available in this

context This method is based on the assumption that degradable

organic carbon (DOC) in respective wastes decays slowly forming

CO2 and CH4 over a few decades CO2 released due to the decomposi-

tion of biomass sources by aerobic bacteria is counted as biogenic ori-

gin and does not contribute to GHGemissions (USEPA 2006)TheCH4

emissions are modeled through 100 years (with 10 years as opera-

tional period and 30 years as restoration period) (Eriksson et al

2005) The CH4 generation rate constant which is varied for each

type of waste and dependent on local climate (ie mean annual tem-

perature andmean annualprecipitation) is selectedbasedon theIPCC

default values (shown in Table 2) The CH4 is collected for 1047298aring pro-

cess and energy recovery system (electricity and heat generation)

during the operational and restoration period while it is released

to the atmosphere without controls after 40 years The CH4 recovery

rate (de1047297ned as total CH4 collectiontotal CH4 production) for the

1047297rst two years isexpected to bezero (dueto insuf 1047297cient gasto operate

the energy recovery equipment) while from the third to tenth yearis 40 (HKEPD 2010c) and 90 during the restoration period (Levis

and Barlaz 2011) This CH4 recovery rate is estimated based on

the current land1047297ll conditions in Hong Kong The Global Warming

Table 1

Summary of four different scenarios

Scenario MSW from RTS to LFE

(tonnes MSW dayminus1)

MSW from RTS to AIF

(tonnes MSW dayminus1)

Ash from AIF to LFE

(tonnes ash dayminus1)

Scenario 1 9000a NAb NA

Scenario 2c 6000 3000 900d

Scenario 3 3000 6000 1800

Scenario 4 NA 9000 2700

a Figure represents thecurrentpractice in HongKongMSW disposal (HKEPD 2010b)b NA means that no MSW or ash is sent to the respective waste disposal facilityc Scenario2 is based on theproposed policy framework for the management of MSW

2005ndash2014 by HKEPD (2005)d Figure is adapted in part from the Engineering Investigation and Environmental

Studies for Integrated Waste Management Facilities Phase 1mdashFeasibility StudyEnviron-

mental Impact Assessment Report (HKEPD 2011) For every 3000 tonnes of MSW

approximately 660 tonnes of bottom ash and 240 tonnes of 1047298y ash and air pollution

control residues (after cementation) would be generated after combustion in AIF

every day A linear correlation between the amount of generated ash and the amount

of combusted MSW in AIF is assumed

WENT landfill

extension

Advanced

incineration facility

OITF

NLTS

IETS

IWTS

WKTS

Biogenic carbon storage

Unrecoverable

MSW

Landfill gas emissions

Energy recovery system

Bottom ash fly ash

and APC residues

Heat

Electricity

Electricity

Stack discharge system

Energy recovery system

CH4 emissions

Avoided CO2

Avoided CO2

Avoided CO2

CO2 emissions

System boundary

CO2 sinks

70 km

54 km

90 kmWENT landfill

Fig 1 Superstructure of the interrelations among the refuse transfer stations (RTS) WENT land1047297ll extension (LFE) and advanced incineration facility (AIF) used in this study OITF

Outlying Islands Transfer Facilities NLTS North Lantau Transfer Station IETS Island East Transfer Station IWTS Island West Transfer Station WKTS West Kowloon Transfer

Station APC Air Pollution Control WENT West New Territories The distance traveled is shown in round trip

501KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 49

Potential (GWP) applied in this study for CH4 is 25 (a 100-year time

horizon) (IPCC 2007) Typically the production of CH4 does not

begin immediately after deposition of the waste as aerobic decompo-

sition takes place prior to anaerobic decomposition Hence in this

study it is estimated that the CH4 would only be produced after

6 months (as recommended by the IPCC) in the year after MSW depo-

sition Land1047297ll gas (LFG) is a mixture of CH4 CO2 and a trace amount

of nitrogen nonmethane organic compounds and other gasses The

fraction of CH4 in generated LFG is 50 (by volume) in this analysis

( Jaramillo and Matthews 2005) Given the same amount of MSW an

unmanaged land1047297ll produces less CH4 than an anaerobic managedland1047297ll Hence the CH4 correction factor is assigned by the IPCC to

re1047298ect the way MSW is managed and the effect of site con1047297guration

and management practices on CH4 generation (IPCC 2006) The CH4

correction factor (in fraction) used in this study is 10 assuming that

the LFE is an anaerobic managed land1047297ll Some uncollected CH4 is

oxidized to CO2 in the soil or other materials covering the waste

from LFE CH4 oxidation is assumed to reduce the CH4 emissions by

10 as suggested by the IPCC (2006) and as used in HKEPD (2010c)

N2O emissions from the land1047297ll are assumed to be insigni1047297cant as

recommended by the IPCC and are excluded from this analysis

(IPCC 2006) The data for calculating the land1047297ll CH4 emissions is

summarized in Table 2

223 GHG reductions from heat and electricity generated due to energyrecovery system

In Hong Kong land1047297lls part of the collected CH4 is sent to an

energy recovery system for electricity and heat production to meet

on-site needs while the remaining is 1047298ared into the atmosphere Of

the total amount of recovered CH4 10 is used for electricity genera-

tion 50 for heat production (by an ammonia stripping plant in a

land1047297ll leachate treatment process) and the remaining 40 is 1047298ared

(HKEPD 2009) Complete combustion is assumed at 1047298aring process

only CO2 is released into atmosphere after 1047298aring However the

released CO2 is counted as biogenic in origin and not included in

this study (IPCC 2006) The heating value of land1047297ll CH4 used in

this context is 377 MJ mminus3 (Morris 2010) while the ef 1047297ciency

of a gas turbine is modeled as 035 (HKEMSD 2002) Producing elec-

tricity and heat from the recovered CH4 can contribute to a reduction

of the usage of fossil fuel resources and amelioration of GHG impacts

The recovered electricity is compared with the electricity emission

factor from China Light amp Power (CLP) Company at a value of

059 kg CO2e kWhminus1 (CLP 2011a) This electricity emission factor

corresponds to carbon dioxide emitted by CLP Company in producing

one kilowatt hour of electricity in Hong Kong In this context 059 kg

of carbon dioxide equivalents is generated when producing one kilo-

watt hour of electricity For heat production the ef 1047297ciency of a boiler

used is 080 (Damgaard et al 2011) In Hong Kong about 30 of hot

water is generated by electricity-1047297red water heaters and 70 of that

is generated by gas-1047297red water heaters or boilers (Hao et al 2008)The emission factor of Lique1047297ed Petroleum Gas (LPG) for hot water

production adopted in this analysis is 00624 g CO2e kJminus1 (Leung

and Lee 2000) Considering the hot water ratio production and

emission factors from electricity and LPG the effective emission

factor for heat production in Hong Kong is 0093 g CO2e kJminus1 This

effective emission factor is used to estimate the GHG offsets due to

the heat generated from recovered CH4

224 GHG reductions from biogenic carbon storage

Signi1047297cant portions of land1047297lled biogenic carbon (eg putrescibles

woods and papers) are not completely decomposed by the anaerobic

condition and the carbon is stored in the land1047297ll body Thus the land-

1047297ll serves as a long-term anthropogenic sink for GHG calculation

(USEPA 2006) However the fossil carbon that remains in the land1047297llis notcounted as storedcarbon because it is of fossilorigin andalready

considered exists in its natural state The biogenic carbon storage is

calculated using a method as discussed in IPCC (2006) In this context

thefractionof DOCthat canbe decomposed in theanaerobic condition

in LFE is assumed to be 05 (mass fraction) In other words 50 of the

disposed DOC would remain in LFE for a long period

23 Modeling details for AIF

On the basis of the GHG emissions and offset estimates for each

individual process the general equation for calculating the net GHG

emissions for AIF is shown in Eq (2)

GHG AIF frac14 GHG AIFTrans thorn GHGStackminus

GHG AIFGen eth2THORN

Table 2

Hong Kong discarded municipal solid waste (MSW) characterization data

Waste component Waste

composition

()a

Dry matter

content

()b

Total carbon

content in dry

weight ()c

Fraction

of fossil

carbond

Fraction of degradable

organic carbon on

wet basise

CH4 generation

rate constant

(yearminus1)f

Heating value

(Btu lbminus1)gHeating value

(kJ kgminus1)hEnergy content

of each waste

component (kJ)

Glass 41 0900 0 001 0 0 60 140 57

Metals 19 0900 0 001 0 0 300 698 133

Paper 220 0723 0419 001 0365 0070 7200 16747 3684

Plastics 213 0810 0697 100 0 0 14000 32564 6936

Putrescibles 402 0231 0470 0 0186 0400 2000 4652 1870Textiles 26 0624 0490 020 0240 0070 7500 17445 454

Woodrattan 32 0684 0493 0 0430 0035 8000 18608 596

Household hazardous

wastesi12 0900 0030 100 0 0 3000 6978 837

Othersij 34 0900 0030 100 0 0 3000 6978 237

Totalk 100 13880

a HKEPD (2010b) Figure may not add up to total due to rounding offb Dry matter contents of paper plastics putrescibles textiles and woodrattan are adapted from the HKSAR Government unpublished report Dry matter contents of glass metals

household hazardous wastes and others are based on the 2006 IPCC Guidelines default valuec Total carbon contents in dry weight of paper plastics putrescibles textiles and woodrattan are adapted from the HKSAR Government unpublished report Total carbon con-

tents in dry weight of glass metals household hazardous wastes and others are based on the 2006 IPCC Guidelines default valued IPCC (2006)e IPCC (2006) Degradable organic carbons on wet basis of paper and putrescibles are modi1047297ed according to the total carbon content in dry weightf IPCC (2006) Climate for Hong Kong is considered moist and wet tropical under IPCC Climate Zone De1047297nitiong Brunner (2002)h 1 btu lbminus1 times 2326 = 1 kJ kgminus1

i Household hazardous waste and others are categorized as other inert waste under IPCCs Waste Categorization j Others include bulky items and other miscellaneous materialsk Figure may not add up to total due to rounding off

502 KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 59

where GHG AIF = net GHG emissions from AIF GHG AIFTrans = GHG

emissions from MSW and ash transport for AIF GHGStack = GHG

emissions from stack discharge system and GHG AIFGen = GHG reduc-

tions from electricity generated due to energy recovery system

231 GHG emissions from MSW and ash transport

The distance traveled is modeled based on the average distance

between the three RTSs (ie IETS IWTS and WKTS) and the IWMF

site at Shek Kwu Chau (HKEPD 2011) The MSW transport distanceto IWMF site is assumed to be 54 km (round trip) and the distance

traveled for ash hauling from the IWMF site to the WENT land1047297ll is

about 90 km (round trip) Similar to the LFE only one trip per day

for MSW hauling from each RTS to the AIF and ash disposal from

the AIF to the LFE is assumed The GHG emission factor accounting

for MSW hauling and ash disposal is identical to the aforementioned

MSW hauling in LFE

232 GHG emissions from stack discharge system

The CO2 emissions from AIF due to the stack discharge system

are calculated using 2006 IPCC guidelines based on the basic carbon

stoichiometry calculation in the waste streams (IPCC 2006) Only

the MSW fossil carbon content is responsible for GHG emissions

Biogenic CO2 emitted by biomass materials contained in the waste

which is considered as carbon neutral is not counted as a GHG source

(USEPA 2006) CH4 and N2O emitted from AIF are excluded in this

study This is because emissions of CO2 are typically more signi1047297cant

than CH4 and N2O as reported by the IPCC (2006) Data for the waste

fraction of each component dry matter content total carbon content

in dry matter and the fraction of fossil carbon can be found in Table 2

An oxidation rate is used in calculation to estimate the conversion

ef 1047297ciency of waste products to CO2 A 97 oxidation rate is used in

this study as recommended in the EIA report (HKEPD 2011)

233 GHG reductions from electricity generated due to energy recovery

system

The energy gained from the MSW combustion in the proposed

AIF displaces the electricity generated by the CLP Company The

heating value in MSW combustion is 13880 kJ kgminus1 MSW (detailedinformation on Table 2) calculated using the typical heating value

of MSW components provided by Brunner (2002) as used by Choy

et al (2004) The net amount of energy recovered during the MSW

combustion depends on the process conversion ef 1047297ciency The ef 1047297-

ciency of the steam turbine used to estimate the electricity generation

in this study is 0197 (HKEMSD 2002) This conversion ef 1047297ciency

is almost similar to the value used in other studies which is 019

(Kaplan et al 2009 Morris 2010) Taking the ef 1047297ciency of steam

turbine into account the base case net electricity generation from

AIF is about 760 kWh tonneminus1 This assumes that 30 of generated

electricity is used on-site while the remaining is sent to an electricity

grid for export (HKEMSD 2002) Also 4 of the exported electricity is

lost during the transmission and distribution process to other users

(CLP 2011b)

24 Energy recovery system and sensitivity analyses on CH 4 recovery

rate in LFE electricity emission factor of CLP Company and MSW heating

value in AIF

As abovementioned an energy recovery system would be applied

in the proposed LFE and AIF in Hong Kong Although it is a well-

known fact that most modern land1047297ll and incineration facilities are

equipped with energy recovery systems to promote environmental

and energy sustainability it is worthwhile to study the relative conse-

quences and bene1047297ts from a carbon footprint perspective of applying

an energy recovery system as compared to facilities without energy

recovery system Also there are some uncertainties in this model

and input parameters that signi1047297cantly affect the GHG emissions are

investigated Sensitivity analyses are done on key input parameters

(eg CH4 recovery rate in land1047297ll electricity emission factor MSW

heating value) to serve as a guideline to policy makers concerning

robust parameters that would have a considerable effect on the results

hence extra caution would be taken while applying this model

3 Results and discussion

31 Net GHG emissions from different scenarios

The calculated GHGemissions from BAU (Scenario 1) and different

proposed scenarios are depicted in Fig 2 The net GHG emissions

for all scenarios range from 199 to 1116 kg CO2e tonneminus1 Given

the same composition of MSW the results re1047298ect that net GHG emis-

sions from LFE are noticeably higher than AIF with BAU (Scenario 1)

as the worst scenario The trend indicates that more GHG emissions

could be reduced if more MSW was disposed of via AIF Compared

to BAU (Scenario 1) the percentages of net GHG emission reductions

are approximately 274 547 and 822 for Scenarios 2 3 and 4

respectively The implementation of the proposed policy framework

2005ndash2014 (Scenario 2) by the HKSAR Government would reduce

the GHG emissions as compared to BAU (Scenario 1)

32 Contribution of GHG emissions from individual sub-processes in LFE

and AIF

Besides investigating the net GHG emissions from the overall LFE

and AIF within the de1047297ned system boundary Fig 3 shows the contri-

bution of GHG emissions from each individual sub-process from the

respective waste disposal facilities It can be seen that the land1047297ll

CH4 emissions contribute to the highest GHG emissions as illustrated

in Fig 3a The CH4 emissions are a major GHG source for land1047297lls The

characterization of CH4 to CO2e with a GWP of 25 contributes signi1047297-

cantly to GHG emissions The electricity and heat generated from en-

ergy recovery system help to offset the GHG emissions from the LFE

but biogenic carbon storage is the most signi1047297cant process for reduc-

ing the carbon footprint in LFE The land1047297lled biogenic carbon that is

not decomposed by anaerobic bacteria is stored in land1047297lls and itssubsequent CO2 release does not contribute to the addition of carbon

in atmospheric stock yielding a great portion of carbon offsets in LFE

Fig 3b shows the GHG emissions from each individual process in AIF

GHG emissions are resulted predominantly from the stack discharge

system due to MSW combustion while the electricity generation

1116

811

506

199

0

20

40

60

80

100

120

Scenario 1(LFE only)

Scenario 2(LFEAIF)

Scenario 3(AIFLFE)

Scenario 4(AIF only)

G H G E m i s s i o n s ( k g C O 2 e t o n n e M S W )

Fig 2 Comparison of GHG emissions for different scenarios Scenario 1 represents

9000 tonnes MSW to LFE per day Scenario 2 represents 6000 tonnes MSW to LFE

and 3000 tonnes MSW to AIF per day Scenario 3 represents 3000 tonnes MSW to

LFE and 6000 tonnes MSW to AIF per day and Scenario 4 represents 9000 tonnes

MSW to AIF per day

503KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 69

from the energy recovery system contributes to the highest GHG off-

sets The use of MSW to generate electricity in AIF provides betterGHG offsets compared to LFG (ie recovered CH4) to generate heat

and electricity in LFE This can be partly attributed to the fact that

land1047297ll CH4 has a lower heating value than MSW combustion and

only the biodegradable portion of MSW in a land1047297ll contributes to

the CH4 generation Furthermore it is assumed that the CH4 emis-

sions are not fully recovered due to inef 1047297ciencies in the land1047297ll

gas collection system and the aforementioned land1047297ll operating

systems indicate that not all recovered CH4 is used for electricity

and heat production Fig 3a and b also indicates that the contribution

of GHG emissions from the transport process is relatively insigni1047297cant

as compared to the other individual sub-processes This is mainly due

to the small land area of Hong Kong where the distances traveled

between RTS and the respective waste disposal facilities are rela-

tively short A summary of GHG emissions or reductions from indi-vidual sub-processes for all four scenarios are shown in Table A1

(Supplementary data) The results in Fig 3 provide valuable infor-

mation to policy makers to improve the performance of facility by

reducing the GHG emissions The results could serve as guidelines

for improvement of processes from the respective waste disposal facil-

ities which signi1047297cantly release or reduce the GHG emissions

33 Comparison of LFE and AIF with and without energy recovery system

As previously stated the relative GHG reductions from LFE and

AIF with or without an energy recovery system are investigated in

this study The results of all four scenarios are illustrated in Fig 4 As

expected net GHG emissions for waste disposal facilities with energy

recovery systems are lower compared to those facilities without these

systems However this phenomenon is more signi1047297cant for AIF

AIF with an energy recovery system emits 4352 kg CO2e tonneminus1

less compared to AIF without this system while LFE with an energy

recovery system emits 724 kg CO2e tonneminus1 less than LFE without

this system Apart from this result it is interesting to note that scenar-

ios without an energy recovery system in which BAU(Scenario 1) and

Scenario 4 are the best and worst case respectively exhibit a reverse

ranking order in terms of GHG emissions In other words without

the energy recovery systems LFE releases less GHG emissions as

11

5043

-724

-3215

1116

-500

-300

-100

100

300

500

Scenario 1 (LFE only)

G H G E m i s s i o n s ( k g C O 2 e t o n

n e M S W )

-500

-300

-100

100

300

500

G H G E m i s s i o n s ( k g C O 2 e t o n

n e M S W )

Transport (MSW Hauling)

Energy Recovery System (Electricity and Heat

Generation)

Biogenic Carbon Storage (Anthropogenic Sink)

Net GHG Emissions

a

13

4538

-4351

199

Scenario 4 (AIF only)

Transport (MSW Hauling and Ash Disposal)

Stack Discharge System

Energy Recovery System (Electricity Generation)

Net GHG Emissions

b

Landfill CH4 Emissions

Fig 3 Contribution of GHG emissions from different individual processes (a) Scenario 1 (LFE only) and (b) Scenario 4 (AIF only)

1116

811

506

199

1840

2744

3648

4551

0

50

100

150

200

250

300350

400

450

500

Scenario 1(LFE only)

Scenario 2(LFEAIF)

Scenario 3(AIFLFE)

Scenario 4(AIF only)

G H G E m i s s i o n s ( k g C O 2 e t o

n n e M S W )

With Energy Recovery System Without Energy Recovery System

Fig 4 Comparison of GHG emissions for different scenarios with and without energy

recovery system

504 KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 79

compared to AIF The remarkable GHG emission reductions for AIF in-

dicate that the energy recovery systemin AIF plays a more crucial role

in contributing to GHG offsets as compared to LFE This is owing to the

fact that AIF is capable of generating an order of magnitude more elec-

tricity than LFE given the same amount and composition of MSW

Hence it provides a huge advantage on GHG reductions and fossil

fuel offsets As a result policy makers are advised to provide more

incentives and enhance ef 1047297ciency of the technology of energy recov-

ery since it provides a promising technique for reducing GHG emis-sions and fossil fuels consumption

34 Summary of sensitivity analyses

Given the complexity of the systems studied and some uncer-

tainties about primary data collection the parametric sensitivity anal-

yses presented in this paper provide a better understanding of the

relationship between waste disposal facilities and the degree to

which variations in key input parameters might alter 1047297nal conclu-

sions The key input parameters used in this study are recovery rate

of land1047297ll CH4 electricity emission factor of CLP Company MSW

heating value in the AIF and ef 1047297ciencies of gas turbine (for LFE) and

steam turbine (for AIF) In this context the sensitivity analyses on

the ef 1047297ciencies of gas turbine and steam turbine are not studied as

they are varied according to the models purchased and should be

constant throughout the operational period For the recovery rate of

land1047297ll CH4 the range of 40 to 60 is chosen based on the land1047297ll

CH4 data collected from the closed and existing land1047297lls in Hong

Kong (HKEPD 2010c) For the variations of electricity emission

factors the values are chosen based on the sustainability report of

CLP Company (CLP 2011a) In view of the MSW heating value the

range of 550 kWh tonneminus1 to 850 kWh tonneminus1 is selected based

on the 1047297ndings as reported by Kaplan et al (2009) Fig 5 shows the

sensitivity analysis with a variation of land1047297ll CH4 recovery rate rang-

ing from 40 to 60 during the operational phase The comparison is

done between Scenario 1 and Scenario 4 to examine the conse-

quences of increasing the CH4 recovery rate in a land1047297ll system com-

pared to MSW being incinerated From this 1047297gure it can be observed

that LFE is sensitive to the CH4 recovery rate Net GHG emissions arereduced approximately 54 for every 10 increment of CH4 recovery

rate This drastic change is mainly due to CH4 that has a GWP of 25 for

GHG emissions It reduces CO2e emissions considerably if it is not

released to the atmosphere Besides the higher CH4 recovery rate in-

dicates that more CH4 is recovered for electricity and heat production

rendering more GHG offsets Based on a trial and error calculation

from Fig 5 the breakeven CH4 recovery rate for LFE to emit equal

GHG emissions compared to AIF is 56 and LFE releases less GHG

emissions than AIF when the CH4 recovery rate is above 56 In addi-

tion it is worthwhile to note that LFE achieves zero GHG emissions

when the CH4 recovery rate is at 586 Above this recovery rate

the LFE shows negative GHG emissions With advancing technology

institutions should enhance standards for land1047297ll performance by en-

couraging a higher recovery rate of land1047297ll CH4 emissions throughout

its entire life cycle

GHG offsets by electricity generated from land1047297

ll CH4 and MSWcombustion depend on the fuel mix composition of the displaced

electricity from a power plant Electricity generated from a low

carbon intensive source (eg natural gas) would emit lower GHG

emissions than high carbon intensive source (eg coal) Taking the

electricity emission factors as targeted by CLP Company in 2035

and 2050 (CLP 2011a) a sensitivity analysis on different electricity

emission factors is analyzed to investigate the impact on net

GHG emissions for all four scenarios As shown in Fig 6 with the

change of the electricity emission factors of the CLP Company from

059 kg CO2e kWhminus1 to 020 kg CO2e kWhminus1 the GHG emissions of

LFE increase 284 kg CO2e tonneminus1 while the GHG emissions of AIF

increase 2876 kg CO2e tonneminus1 or almost 145 times more than the

base case scenario This indicates that AIF is more sensitive to the var-

iation of electricity emission factors as compared to LFE When the

electricity emission factor is set at 059 kg CO2e kWhminus1 Scenario 4

is the best among other scenarios The net GHG emissions for all

scenarios are almost identical when the electricity emission factor is

set at 045 kg CO2e kWhminus1 However Scenario 4 contributes the

highest GHG emissions among other scenarios when the electricity

emission factor achieves a target of 020 kg CO2e kWhminus1 The results

indicate that the recovered electricity generated from AIF is vulnera-

ble to policies of national fuel mix composition for electricity pro-

duction This is an important area for policy makers to consider

when selecting appropriate waste disposal facilities While the

HKSAR Government promotes fuel switching by applying cleaner en-

ergy in this region to reduce carbon intensity there is a tendency that

LFE is better than AIF in view of carbon footprint due to the prepon-

derance of less GHG emissions generated from cleaner energy

One of the factors affecting the amount of energy produced fromMSW combustion in AIFis MSW heating value Thedifferent composi-

tion and moisture content of MSW generate a varying MSW heating

value A sensitivity analysis can be performed to investigate the

net GHG emissions due to the variation of the MSW heating value In

Landfill CH4 Recovery Rate

1116

516

-85

991991991

-20

0

20

40

60

80

100

120

605040

G H G E m i s s i o n s ( k g C O 2 e t o n n e M S W )

Scenario 1 (LFE only) Scenario 4 (AIF only)

Fig 5 Comparison of GHG emissions from Scenario 1 (LFE only) with variation of land1047297ll

CH4 recovery rate to Scenario 4 (AIF only)

0

50

100

150

200

250

300

350

Base Case -CLP (2011) CLP (2035) CLP (2050)

G H G E m i s s i o n s ( k g

C O 2 e t o n n e M S W )

Scenario 1(LFE only)

Scenario 2(LFEAIF)

Scenario 3(AIFLFE)

Scenario 4(AIF only)

Fig6 Comparison of GHG emissions for different scenarios withdifferent electricity emission

factors in Hong Kong CLP (2011) = electricity emission factor at 059 kg CO2e kWhminus1

CLP (2035) = electricity emission factorat 045 kg CO2e kWhminus1 CLP (2050) = electric-

ity emission factor at 020 kg CO2e kWhminus1

505KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 89

Fig 7 the variation of MSW heating value entails different outcomes

of net GHG emissions from AIF compared to LFE It can be seen that

the higher the MSW heating value the lower the net GHG emissions

from AIF This is mainly ascribed to the fact that a higher MSW

heating value generates more energy during the energy recovery

system producing more electricity and hence more electricity is

displaced from the power plant The GHG emissions of AIF reduce

573 kg CO2e tonneminus1 for every increment of 100 kWh tonneminus1 of

MSW heating value Meanwhile based on a trial and error calculation

from Fig 7 the breakeven MSW heating value for AIF to release equal

amount of GHG emissions compared to LFE is 598 kWh tonneminus1

However policy makers should note that not all discarded MSW is a

viable source for electricity generation As it can be seen from

Table 2 the MSW components that contribute to high energy content

are mainly paper and plastics The energy content from putrescibles is

relatively lower than paper and plastics (due to a relatively lowerheating value) regardless of the fact that it contributes to the highest

waste fraction among other MSW components Also glass and metals

are not suitable for combustion due to low heating values with 004

and 010 of total MSWenergy content respectively In view of improv-

ing the MSW heating value of the energy recovery system in AIF it

is suggested to discard putrescibles via other treatment methods

(eg composting or anaerobic digestion) and more pre-sorting effort

could be done on waste components particularly with low heating

values (eg glass and metals) before undergoing combustion process

in AIF

4 Conclusions

The modeling approach used for calculating GHG emissions fromboth LFE and AIF in this study is explained explicitly in this paper It

provides a framework for policy makers to consider the performance

of GHG emissions of different waste disposal scenarios The aggrava-

tion or mitigation of GHGs from the waste sector depends on the tech-

nology and the ef 1047297ciency of waste disposal facilities Based on the data

collected assumptions made and system boundary de1047297ned in this

study the net GHG emissions from AIF are less than LFE The 1047297ndings

indicate that the implementation of the proposed waste management

policy framework 2005ndash2014 (Scenario 2) by the HKSAR Government

would emit less GHGthan thecurrent practice in Hong Kong Based on

this study some substantive measures to be taken to tackle the GHG

emissions in the waste sector include the reduction of land1047297ll CH4

emissions to the atmosphere through a higher CH4 recovery rate and

the enhancement of heat and electricity generation through improved

performance and ef 1047297ciency of energy recovery system Nevertheless

due to heterogeneous characteristics within MSW and complex

multi-criteria factors affecting the performance of waste disposal

facilities policy makers should be aware that the variation of some

key inputs as suggested in the sensitivity analyses might alter the

overall impact on net GHG emissions

The relentless growth in the volume of MSW constitutes both a

threat and an opportunity to society depending on how we treat the

waste One opportunity is to convert waste to wealth by enhancingthe potential utilization of energy recovery systems Some results in

this study demonstrate that AIF has a great potential for reducing

GHG emissions via electricity generated from energy recovery system

Substantial energy and carbon offsets can be achieved by capitalizing

on energy conservation through resource recovery of MSW Economic

incentives can be provided to boost energy recovery in the waste sec-

tor In addition citizen acceptance of proposed waste management

policies is critical and should be taken into consideration Strong

local opposition from the public will incur delays for waste disposal

facilities to be commissioned The policy makers have the obligations

to pursue a sustainable waste management framework that is envi-

ronmentally sound economically feasible and socially acceptable

Supplementary data to this article can be found online at http

dxdoiorg101016jscitotenv201304061

References

Assamoi B Lawryshyn Y The environmental comparison of land1047297lling vs incinerationof MSW accounting for waste diversion Waste Manag 2012321019ndash30

Bogner J Ahmed MA Diaz C Faaij A Gao Q Hashimoto S et al Waste management InMetz B Davidson OR Bosch PR Dave R Meyer LA editors Contribution of WorkingGroup IIIto theFourth AssessmentReport of theIntergovernmental Panel on ClimateChange 2007 Cambridge United Kingdom and New York NY USA CambridgeUniversity Press 2007 p 585ndash618

BrunnerCR Waste-to-energycombustionIn Tchobanoglous G Kreith F editorsHand-book of solid waste management 2nd ed New York McGraw-Hill 2002 p 137

Choy K Porter J Hui C McKay G Process design and feasibility study for small scaleMSW gasi1047297cation Chem Eng J 200410531ndash41

Christensen TH Simion F Tonini D Moller J Global warming factors modeled for 40generic waste management scenarios Waste Manag Res 200927871ndash84

CLP (Company Light Power Group) 2011 online sustainability report 2011a

CLP (Company Light Power Group) 2011 annual report 2011bDamgaard A Manfredi S Merrild H Stensoslashe S Christensen T LCA and economic eval-

uation of land1047297ll leachate and gas technologies Waste Manag 2011311532ndash41DEFRA (Department for Environment Food and Rural Affairs) 2011 guidelines to

DefraDECCs GHG conversion factors for company reporting methodology paperfor emission factors 2011

Eriksson O Carlsson Reich M Frostell B Bjorklund A Assefa G Sundqvist JO et alMunicipal solid waste management from a systems perspective J Clean Prod 200513241ndash52

HammondG Time togive dueweight to thecarbon footprintissue Nature2007445(7125)256

Hao X Yang H Zhang GT A new way for land1047297ll gas utilization and its feasibility inHong Kong Energy Policy 2008363662ndash73

HKBEC (Hong Kong Business Environment Council) The Hong Kong business guide toemission reduction [Internet] [cited 2012 May 23] Available from httpwwwclimatechangebusinessforumcomen-usghg 2012

HKEB (Hong Kong Environment Bureau) Hong Kongs climate change strategy andaction agenda Consultation Document 2010

HKEB (Hong Kong Environment Bureau) Take action now for proper waste manage-ment 2011

HKEMSD (Hong Kong Electrical amp Mechanical Services Department) Study on the po-tential applications of renewable energy in Hong Kong Stage 1 study report 2002

HKEPD (Hong Kong Environmental Protection Department) A policy framework forthe management of municipal solid waste (2005ndash2014) 2005

HKEPD (Hong Kong Environmental Protection Department)North EastNew Territories(NENT) land1047297ll extensions environmental impact assessment report 2007

HKEPD (Hong Kong Environmental Protection Department) West New Territories(WENT) land1047297ll extensions environmental impact assessment report 2009

HKEPD (Hong Kong Environmental Protection Department) Environmental perfor-mance report 2010 [Internet] [cited 2012 May 23] Available from httpwwwepdgovhkepdmiscerer2010indexhtml 2010

HKEPD (Hong Kong Environmental Protection Department) Monitoring of solid wastein Hong Kong Waste statistic for 2010 2010b

HKEPD (Hong Kong Environmental Protection Department) A study of climate changein Hong Kongmdashfeasibility study 2010 2010c

HKEPD (Hong Kong Environmental Protection Department) Engineering investigationand environmental studies for integrated waste management facilities phase 1mdash

feasibility study environmental impact assessment report 2011

1116 1116 1116 1116

199

1396

823

-324

-60

-40

-20

020

40

60

80

100

120

140

160

760 kWhtonne(Base Case)

550 kWhtonne 650 kWhtonne 850 kWhtonne

G H G E m i s s i o

n s ( k g C O 2 e t o n n e M S W )

MSW Heating Value

Scenario 1 (LFE only) Scenario 4 (AIF only)

Fig 7 Comparison of GHG emissions from Scenario 4 (AIF only) with variation of MSW

heating value to Scenario 1 (LFE only)

506 KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507

8162019 Science of the Total Environment

httpslidepdfcomreaderfullscience-of-the-total-environment 99

Hoornweg D Bhada-Tata P What a waste a global review of solid waste managementUrban development series knowledge papers no 15 Washington DC The WorldBank 2012

IPCC (Intergovernmental Panel on Climate Change) 2006 IPCC guidelines for nationalgreenhouse gas inventories Waste vol 5 2006

IPCC (Intergovernmental Panel on Climate Change) Climate change 2007 the physicalscience basis contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change In Solomon S Qin D Manning MChen ZM Marquis M Averyt KB Tignor M Miller HL editors New York CambridgeUniversity Press 2007

Jaramillo P Matthews HS Land1047297ll-gas-to-energy projects analysis of net private and

social bene1047297ts Environ Sci Technol 2005397365ndash

73Kaplan PO Decarolis J Thorneloe S Is it better to burn or bury waste for clean electric-ity generation Environ Sci Technol 200943(6)1711ndash7

Leung D Lee Y Greenhouse gas emissions in Hong Kong Atmos Environ 2000344487ndash98

Levis JW Barlaz MA Is biodegradability a desirable attribute for discarded solid wastePerspectives from a national land1047297ll greenhouse gas inventory model Environ SciTechnol 2011455470ndash6

Lo A Chinas response to climate change Environ Sci Technol 2010445689ndash90MoharebaAK Warithb MA Diazb RModelling greenhouse gas emissionsfor municipal

solid wastes management strategies in Ottawa Ontario Canada Resour ConservRecycl 2008521241ndash51

Monni S From land1047297lling to waste incineration implications on GHG emissions of different actors Int J Greenh Gas Con 2012882ndash9

Morris J Bury or burn North America MSW LCAs provide answers for climate impactsand carbon neutral power Environ Sci Technol 2010447944ndash9

Ng J Green groups plead against incinerator site South China Morning Post 2011 Mar18

Ng J Neighbours mull legal bid to stop incinerator South China Morning Post 2012 Jan12

Schiermeier Q Climate and weather extreme measures Nature 2011477148ndash9Tang H Govt opts not to use country park for land1047297ll Hong Kongs Information Service

Department 2011 [Jan 4]

UNEP (United Nations Environment Programme) Developing integrated solid wastemanagement plan Training manualWaste characterization and quanti1047297cation withprojections for future vol 1 2009

UNEP (United Nations Environment Programme) Waste and climate change globaltrends and strategic framework 2010

USEPA (USEnvironmentalProtection Agency) Solidwaste management and greenhousecitiesmdasha lifecycleassessmentof emissionsand sinks 3rded 2006 [Washington DC]

Vergara SE Damgaard A Horvath A Boundaries matter greenhouse gas emissionreductions from alternative waste treatment strategies for Californias municipalsolid waste Resour Conserv Recycl 20115787ndash97

507KS Woon IMC Lo Science of the Total Environment 458ndash460 (2013) 499ndash507