A review on technological options of waste to energy for effective 2017 (1)

Prévia do material em texto

A review on technological opt ions of w aste to energy for effect ive
m anagem ent of m unicipal solid w aste
Atu l Kum ar, S.R. Sam adder ⇑
Department of Environmental Science & Engineering, Indian Institute of Technology (Indian School of Mines), Dhanba d 826004, India
a r t i c l e i n f o
Article history:
Received 21 April 2017
Revised 25 August 2017
Accepted 26 August 2017
Available on line xxxx
Keywords:
Municipal solid waste managem ent
Waste to energy
Waste to energy techn ologies
Developing countries
Developed countries
Review
a b s t r a c t
Approxim ate ly one-fourth popu lat ion across the w orld rely on t rad itional fuels (kerosene, nat ural gas,
biom ass residue, firewood, coal, an im al dung, etc.) for dom estic use despite sign ifican t socioecon om ic
and technological developm ent. Fossil fuel reserves are being exploited at a very fast rate to m eet the
increasing energy dem ands, so there is a need to find alternat ive sources of energy before a ll the fossil
fuel reserves are dep leted. Waste to energy (WTE) can be considered as a poten tial alterna tive source
of energy, w hich is econom ically viable and environm enta lly susta inable. The present study reviewed
the curren t global scenario of WTE technological op tions (incineration , pyrolysis, gasificat ion , anaerobic
digestion, and landfilling w ith gas recovery) for effect ive energy recovery and the challenges faced by
developed and developing coun tries. Th is review will provide a fram ework for evaluat ing WTE techn o-
logical op tions based on case stud ies of developed and develop ing coun tries. Unsanitary landfilling is
the m ost com m only pract iced waste disposal op tion in the developing countries. How ever, developed
coun tries have realised the potent ial of WTE technologies for effective m unicipal solid w aste manage-
m ent (MSWM). This review w ill help the policy m akers and the im plem ent ing authorities involved in
MSWM to understand t he curren t sta tus, challenges and barriers for effective m anagem ent of m unicipal
solid w ast e. This review concluded WTE as a potential r enewable source of energy, which w ill partly m eet
the energy dem and and ensure effect ive MSWM.
Ó 2017 Elsevier Ltd. All righ ts reserved.
Content s
1. In t roduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
1.1. Presen t scenario of waste to en ergy at global level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
1.2. Need of waste to energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
2. Waste generation, characterist ics and composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
3. Heat ing values of m unicipal solid waste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4. Waste to energy options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.1. Therm al conversion technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.1.1. Incinerat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.1.2. Pyrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.1.3. Gasificat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2. Biological conversion t echnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.2.1. Anaerobic d igestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.3. Landfilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
4.3.1. Modelling landfill gas generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
5. Energy recovery potential and econom ics of WTE technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
6. Environm ental and health im pacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
7. Im pact on climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
http ://dx.doi.org/10.1016/j.w asman.2017.08.046
0956-053X/Ó 2017 Elsevier Ltd . All right s reserved.
⇑ Corresponding author.
E-mail address: sukh_sam adder@yahoo.co.in (S.R. Samadder).
Waste Managem ent xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Waste Managem ent
j o u r n al h o m ep ag e: w w w .el sev i er .co m / l o cat e /w asm an
Please cite this article in press as: Kum ar, A., Sam adder, S.R. A review on tech nological op tions of w aste to energy for effective m anagement of m u nicipal
solid w aste. Waste Managem ent (2017), http://dx.doi.org/10.1016 /j.w asm an.2017.08.04 6
8 . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
Acknow ledgem ents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00
1. Int roduct ion
Curren t ly fossil fue ls are the m ost reliable sources of energy,
m eet ing alm ost 84% of the global energy dem and (Shafiee and
Topal, 2009). It is t he tim e t o rea lise the poten tial of w aste t o
energy (WTE) as an opt ion for susta inable solid w aste m anagem en t
and as one of the m ost significant fu tu re renew able energy sources,
wh ich is econom ically viable and environm entally susta inable
(Bajic´ et a l., 2015; Kalyani and Pandey, 2014; Steh lik, 2009). Ali
et al. (2012) concluded that WTE is not on ly sustainab le w aste
m anagem ent solu t ion, bu t a lso an economica lly feasible, especially
for developed coun tries. Baran et a l. (2016) reported t hat ene rgy
recovery from wast e incinerat ion (one of the WTEtechnologies)
is an in tegral part of environm entally sust ainab le w aste m anage-
m ent st rategy. However, Yay (2015) d id not find incinerat ion as al-
ways econom ically sustainable due to it s h igh operational and
m ain tenance cost . WTE is a w ay to recover the energy from w aste
m ate rials in the form of useable heat , elect ricity (by passing gas or
steam through tu rbine ), or fuel (Zhao et al., 2016). WTE technolo-
gies are now con sidered as the m ost su itable opt ions for solving
the w aste re lated problem s.
Th is paper aim s to invest igate m un icipal solid w aste (MSW) as
a poten tial renew ab le energy source. The present paper review ed
the available literat ures on curren t global scenar io of WTE tech-
nologies, necessary requ irem en ts for effect ive energy recovery
and environm ental im pacts of differen t w aste d isposal techn iques.
The WTE technologies adop ted in developed coun tr ies have been
assessed to iden tify the challenges and barr iers for effect ive im ple-
m entation of WTE technologies in developing coun tr ies. In th is
review , 155 article s published in repu ted jou rnals, techn ica l
reports, and books related to WTE technologies (from year 1995
to 2017) w ere selected . More than 70% of the select ed refe rences
were from year 2010 to 2017. For perform ing the review , a system -
atic approach w as follow ed in which d ifferent aspects of WTE w ere
ident ified. The ident ified aspects are: (i) the p resen t status of WTE
at global level, (ii) need of WTE, (iii) generat ion, characteristics and
com posit ional requirem ents for effect ive energy recovery, (iv) WTE
technologica l opt ions and ch allenges associat ed w it h them in
developed and develop ing countrie s, and (v) environm en tal and
health im pacts of WTE facilities. The previously published litera-
tu res and report s were selected and cat egorised based on these
iden t ified aspects. Th is st udy will p rovide a source of scientific
in form at ion and analysed gap in the field of WTE t o the scientific
au dience and wast e m anagem ent planners.
Global u rban popu la tion is increasing at a fast rate (1.5%) than
that of the total popu lation (Ouda et al., 2016). At p resen t, m ore
than half of the w orld populat ion live in u rban areas, so the global
esca lat ion of MSW generation is m ainly due to the population
grow th , urbanisat ion and econom ic deve lopm en t (Kum ar and
Sam adder (in press)). Presen tly, the per capita MSW generation
rate in developed coun tries is m ore t han that of the developing
coun tr ies, because gen erat ion rate depends on econom ic and social
p rosperit y of a country. It w as estim at ed that in com ing decades
the developing countries of Asia and other parts of the w orld w ill
m at ch the MSW generation rate of developed coun tries (Fazeli
et al., 2016). Slow ly, the peop le of deve loping count rie s are adap t-
ing life st yle of deve loped nat ions due t o globa lisation , resu lt ing in
genera tion of large quant it ies of w ast es. Thus, the escalat ion in
MSW generat ion rate is m ain ly due to changing food habits, con-
sum pt ion pat tern and living standards of the urban population
(Khan et al., 2016).
Many researchers have reported t hat recycling is m ore pre-
fe rred opt ion than energy recovery (Tan et al., 2014; Ouda et al.,
2016). It w as observed from previous findings that the coun tries,
w hich exercised h igh rate of energy recovery from w astes had
appreciable rates of recycling, whereas, for the develop ing coun-
t ries w here landfilling is t he m ost prevalen t wast e m anagement
option , recycling rat es w ere low (Achillas et al., 2011). Arafat
et al. (2015) reported the average recoverable energy con ten ts
(in t erm s of electrical energy efficiency) for different com ponen ts
of MSW using different WTE technologies (Fig. 1). From Fig. 1, it
is eviden t that , anaerobic digest ion is the best su ited WTE option
for food and yard wastes, w hereas, gasificat ion is the best WTE
option for t rea ting plast ic wast es. Incinerat ion rem ains an at t rac-
t ive opt ion am ongst all the w aste st ream s (as specified by Arafat
et al., 2015), as it can be used for en ergy recovery from all t he
0 
500 
1000 
1500 
2000 
2500 
3000 
Paper Plastic Textile Food waste Yard waste Wood
En
er
gy
 (k
ca
l/k
g)
Incineration Anaerobic Digestion Gasification
Fig. 1. Energy recovery potential of d ifferen t WTE technologies for d ifferen t MSW stream.
2 A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx
Please cit e this article in press as: Ku m ar, A., Sam add er, S.R. A review on tech nological options of wast e to energy for e ffective managem ent of m u n icipal
solid waste. Waste Managem en t (2017), h ttp://dx.doi.org/10.1016/j.w asm an.2017.08.046
reported w aste st ream s. How ever, othe r types of w astes such as
inert , m et als, glass, etc., w ere not considered in that st udy.
A m ajor challenge, h ow ever, rem ains in iden t ifying better WTE
technologies. There are som e social opposit ions for deve lopm en t of
the WTE facilit ies due to potent ially toxic em issions (Zhao et a l.,
2016). On the other han d, some characte ristics of WTE facilitie s
are also not favourable, such as high cost s and difficult ies in
arranging fund (Zhang e t a l., 2010). How ever, one of the m ajor
problem s of WTE facilit ies is the protest s from local comm unitie s,
especially in developing coun tries w ith h igh popu lat ion densit y
(Ren et al., 2016; Kalyan i and Pandey, 2014). Thus, for successfu l
im plem en tat ion of any WTE facility, it s accep tance by the local
com m unity is im portant (Kikuch i and Gerardo, 2009). Developed
count ries have realised the poten t ial of WTE opt ions and have
started implem ent ing it for e ffect ive w aste m anagem en t
successfully.
1.1. Present scenario of waste to energy a t global level
The w orld popu lat ion w as 3 b illion in 1960, w hich has
increased to 7 b illion in 2011 and it is expected to reach 8.1 billion
by 2025 (FAO, 2013). The dram atic increase in global popu lat ion
coupled w ith econom ic developm en t had led to rapid u rbanisat ion
and industrialisat ion , w h ich changed the consum pt ion pat tern of
the populat ion that ult im a tely lead to the proliferation of MSW
at an alarming rate . Many countr ies star ted adopt ing the WTE
technologies for effect ive m anagem en t of huge quan t ity of w aste
to produce energy. An estim ate by t he In te rnat ional Renewable
Energy Agency, show ed tha t the w orld has a potent ial of generat -
ing approxim ately 13 Giga Watt of energy from WTE sector alone
(IRENA, 2016). The WTE technologies have been great ly m od-
ern ised and pr ioritised especially in t he developed nat ions. In
2012 , USA alone generated 14.5 m illion MWh of elect ricity from
84 WTE facilities (ERC, 2014). Incineration is the m ost w idely used
WTE option in populous countr ies like China (Liu et al., 2006),
wh ich had around 160 incineration plants in operat ion t ill 2010
(Lianghu e t a l., 2014). There w ere abou t 1900 waste incinerat ion
plants in Japan , out of w hich , only 190 incinerat ion plants w ere
equ ipped w ith pow er generat ion facilit ies (Mont ejo et al., 2011),
bu t Bajic´ et al. (2015) reported that on ly 102 wast e incinerat ion
plants w ere in opera tion for elect ricit y generat ion in Japan. Japan
is follow ed by the European Union (m ainly France), and then the
United States in term s of quantity of w aste incinerated (Montejo
et al., 2011). Out of the tot al quan t ity of MSW genera ted , 74% in
Japan , 54% in Denm ark, 50% in both Sw itzerland and Sw eden are
incinera ted (The World Bank, 2012; Psom opoulos et al., 2009). Italy
installed m any anaerobic co-d igestion plan ts w ith capacity ranging
from 50 kW t o 1 MW (Pan ta leo e t al., 2013). The In ternational Solid
Wast e Associat ion (ISWA) repor ted tha t, globally m ore t han 130
million tonnes of MSW per year (10%of the t ot al generated w aste
globally) is t reated to generate elect ricity (ISWA, 2012). A study
carried ou t by Earth Enginee ring Center of Colum bia University
in 2013 regard ing the percen tage of w aste recycled/com posted ,
landfilled or dive rted tow ards WTE facility across different coun-
trie s found that m ost of the developed coun tr ies prefe r to use envi-
ronm en tally susta inable techn iques such as recycling/com posting
and WTE for the m anagem ent of their generated w ast es (ERC,
2014). The European coun tries such as Net herlands, Belgium , Den-
mark, Germ any, Aust ria, Sw eden and Switze rland divert m ost of
their w ast es from landfi ll for recycling and com post ing facilitie s
(Defra, 2013). In Asian countr ies, Singapore recycles 44% of the ir
generated w astes, w h ile in othe r coun tries (m ostly developing),
typ ically 8–11% w astes are recycled (Ngoc and Schnitzer, 2009).
It has been reported that , som e cit ies such as Hanoi, ach ieved recy-
clin g ra te of 20–30%(Velis et al., 2012). Many developing count rie s
such as India, Viet nam , and Malaysia have started recovering
energy from organ ic w astes, bu t at sm alle r scale . Nguyen et al.
(2014) estim a ted t hat, food w ast e alone cou ld m eet up to 4.1%
of Vietnam ’s elect ricity dem and if conver ted into biogas using
anaerobic d igest ion process. The potent ial of WTE technologies
has not yet been recogn ised by m any of the developing
countr ies.
1.2. Need of waste to energy
At t he end of this cen tury, th e global energy dem and is expect ed
to be abou t six t im es m ore than that of t he cu rren t dem and
(Kothari et al., 2010). The current available energy supp ly is m uch
low er than the actual energy requ ired for consum pt ion in m any of
th e developing countries. At presen t , one of the p rim ary sources of
energy th roughou t the w orld is fossil fuels that meet the dem and
of approxim ately 84% of the total elect ricity generat ion (Ouda
et a l., 2016). Due to rapid dep let ion of fossil fuel rese rves, the w orld
needs alt ernat ive sources of energy such as WTE for m itiga ting the
fu tu re energy cr isis (Char ters, 2001). The problem of d isposal of
huge quant ity of generated MSW and the requirem ent of reliable
source of renew able energy are com m on in m any deve lop ing coun-
tr ies. MSW causes se rious environm ental pollu tion, thus it s use
as a potent ial renew able energy source w ould serve the purpose
of m eeting increased energy dem and as w ell as waste disposal.
Technological advancem ent , im proved pollu t ion control sys-
tem s, governm en tal incent ives and st ringen t regu lat ions have
m ade WTE technology a poten tia l alternat ive, especially for the
developed countries. It not only provides a source of energy, but
also reduces t he potent ial ha rm fu l im pacts of w aste on th e envi-
ronm ent . If 1 tonne of MSW is incinerated for electricity generation
instead of landfilling (withou t gas recovery), then 1.3 tonnes of CO2
equ ivalen t em issions can be avoided if equ ivalent CO2 em issions
from fossil fuel based pow er plant s are also considered to generate
th e sam e am oun t of e lectr icity (ASME, 2008). The w aste incine ra-
tion p lan ts w ith energy recovery facility run w ith p re- treat ed
MSW as a prim ary fuel have sligh tly low ne t carbon em ission fac-
tor (0.04–0.14 kg/MJ) com pared to fossil fuel based pow er p lan ts
(Pat um saw ad and Cliffe, 2002). The restrict ions on landfi ll sites
for MSW disposal an d increase in pub lic awareness on environ-
m en tal im pacts of MSW have forced the governm en ts to find more
effective w ays of MSW disposal (Zhao et al., 2016). The land
requ irem en t for WTE facilit ies is m uch less t han that of landfill
facilit ies for handling sam e quant ity of w aste (Jam asb and Nepal,
2010). WTE plan t processing 1 m illion tonnes of w astes per year
has an average w orking life of m ore t han 30 years and requ ires less
th an 100,000 m 2 of land , w hereas a landfi ll for 30 m illion tonnes of
MSW requires a land of 300,000 m 2.
2. Waste generat ion , char acter ist ics and com posi t ion
Before select ion and im plem en tation of WTE technologies, it is
necessary t o know the am ount of w aste generated its characteris-
tics and com posit ions. According to the World Bank report 2012,
th e global MSW generation rate was 1.3 billion tonnes per year
w ith average generat ion rate of 1.2 kg/c/d. The generation rate of
MSW is expected to reach 2.2 billion tonnes per year by 2025
and 4.2 billion t onnes per year by 2050 (Hoornw eg and Bhada-
Tata , 2012). The solid waste generation ra te is d irect ly proport ional
to the Gross Dom est ic Product (GDP) of developin g countries. Fig. 2
dep icts the re lat ionsh ips betw een GDP of some countr ies and their
per capit a MSW generat ion rates. Countries w ere ca tegorised by
In ternational Monetary Fund in to developed and develop ing coun-
tr ies based on GDP per cap ita (Trosch inetz and Mihelcic, 2009). The
countr ies w ith GDP per capita greater than US$ 10,000 per annum
w ere term ed as developed nat ions. Accord ingly, t he coun tries w ith
A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx 3
Please cite this article in press as: Kum ar, A., Sam adder, S.R. A review on tech nological op tions of w aste to energy for effective m anagement of m u nicipal
solid w aste. Waste Managem ent (2017), http://dx.doi.org/10.1016 /j.w asm an.2017.08.04 6
a num erical value of m ore t han 4 [i.e . log10 {GDP per capita (US$/
yea r)}] w ere considered as developed and t he rest of the cou ntries
were considered as the developing coun tries in the present study.
The MSW generat ion rate is direct ly linked w it h overall deve lop -
m ent of a coun try. Most of the coun tries (as p resen ted in Fig. 2)
show ed linear relat ionsh ips bet ween GDP per cap ita and MSW
generat ion ra te per cap ita. This resu lt is consistent w ith the previ-
ously reported studies (Hoornw eg and Bhada-Tata, 2012; Shekdar,
2009). How ever, Med ina (1997) reported a w eak correlat ion
bet w een the w ealt h of a coun try an d MSW generat ion rate.
Another im portan t observat ion from the Fig. 2 is that , a few of
the developed countries such as Icelan d, Japan , Sin gapore, Sw eden ,
Aust ralia, and Norw ay had less MSW generat ion rate as com pared
to the other developed coun tries; th is m ay be at tribu ted to the dif-
feren t definit ions of MSW adopt ed by d ifferent coun tr ies (Aleluia
and Ferrão, 2016) as w ell as t he adopted w aste reduct ion policie s
in countries such as Japan (Tanaka, 2014). The typical w aste gener -
ation rate of developed count rie s ranges from 1.00 to 2.50 kg/c/d
and 0.50 t o 1.00 kg/c/d for developing coun tries (Thit am e et al.,
2010).
For an effect ive m anagem en t of MSW of a city using suitab le
WTE facilities, it is absolut ely essent ial to know the characterist ics
an d com posit ions of the generated w aste (Yadav and Sam adder,
2017). Actual en ergy product ion from MSW is significant ly depen-
den t on these tw o param eters. The characteristics such as part icle
size, m oistu re con ten t , calorific va lue and density (Alelu ia and
Ferrão, 2016) are im portant factors for select ing and developing
an appropriate WTE facilit y. The w aste character ist ics an d com po-
sit ion vary sign ifican t ly across developed and develop ing coun-
t ries, even the cit ies of the sam e country have differen t w aste
characterist ics because of th e h eterogeneous nature of MSW. The
w aste com posit ion in various incom e group coun tries is show n
in Tab le 1 (Hoornw eg and Bhada-Tata, 2012). The physical com po-
sit ion and characteristics of MSW depend upon various factors,
such as socioeconom ic profile,clim atic condit ions of an area,
extent of recycling, collect ion frequency, dem ography, etc. Using
the previously reported st udies on physical classificat ion of
MSW, the w aste stream has been d ivided in to six different com po-
nen ts nam ely; kitchen/yard w aste, paper /cardboard, plast ic, m et-
als and glass, iner t and miscellaneous (Tab le 2). The MSW of
0 
1 
2 
3 
4 
5 
6 
N
EP
A
L
B
A
N
G
LA
D
ES
H
PA
K
IS
TA
N
IN
D
IA
V
IE
TN
A
M
B
H
U
TA
N
PH
IL
IP
PI
N
ES
SR
I L
A
N
K
A
IN
D
O
N
ES
IA
C
H
IN
A
SO
U
TH
 A
FR
IC
A
C
O
LO
M
B
IA
M
A
LA
Y
SI
A
TU
R
K
EY
B
R
A
ZI
L
A
R
G
EN
TI
N
A
R
U
SS
IA
N
 F
ED
ER
A
TI
O
N
U
R
U
G
U
A
Y
C
H
IL
E 
B
A
H
R
A
IN
G
R
EE
C
E 
SA
U
D
I A
R
A
B
IA
SP
A
IN
IT
A
LY
U
N
IT
ED
 K
IN
G
D
O
M
G
ER
M
A
N
Y
IC
EL
A
N
D
B
EL
G
IU
M
IR
EL
A
N
D
N
ET
H
ER
LA
N
D
S
A
U
ST
R
IA
JA
PA
N
U
N
IT
ED
 S
TA
TE
S
SI
N
G
A
PO
R
E
C
A
N
A
D
A
SW
ED
EN
D
EN
M
A
R
K
A
U
ST
R
A
LI
A
SW
IT
ZE
R
LA
N
D
N
O
R
W
A
Y
Log10[GDP per capita (US$/year)] Waste gen (kg/c/d)
Fig. 2. Distr ibu tion of Waste generat ion rate and GDP of the different countries (Waste Atlas, 2016).
Table 1
Average waste com posit ion in various incom e group countries.
Type of countries Organ ic (%) Paper (%) Plast ic (%) Metals and glass (%) Others (%)
Low income group 64 6 9 6 15
Middle incom e group 56 12 13 7 12
High income group 28 30 11 13 18
Table 2
Physical classification of MSW.
Com ponent Material References
Kitchen /yard
w aste
Food w aste (e.g., food and vegetab le refuse, fru it skins, corncob), yard w aste (e.g., leaves, grass, tree
trim mings), etc.
Bajic´ et al. (2015), Qu et al. (2009) and
Eddine and Salah (2012)
Paper/cardboard Paper bags, cardboard , corrugated board, box board, new sprint , magazines, tissue, office paper, and m ixed
paper, etc.
Plastic High-valued plastics [LDPE bott les (sham poo bottles, detergent bottles, etc.), polypropylene bottles (mess
tins made from rigid plastics, etc.), PET bot tles (beverage bott les, etc.)], Low-valued plastics (Polythene
plastic bags, polystyrene plastic packages such as mess tins made from flexible plastics and plastic cup for
yoghurt, ice-cream , etc.) and others.
Metals & glass Ferrous (e.g., food cans, etc.), non-ferrous (e.g., alumin ium cans, foil, ware, and bimetal, etc.), wire, fence,
knives, bottle covers, etc., and bot tles, glassware, ligh t bulbs, ceramics, etc.
Iner t Stones and silt , soil, ash, dust, oth er inorgan ic mater ial, etc.
Miscellaneous Discarded clothes, rags, leather , rubber, used batt eries, m edical w aste, nappies/san itary product s, etc.
4 A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx
Please cit e this article in press as: Ku m ar, A., Sam add er, S.R. A review on tech nological options of wast e to energy for e ffective managem ent of m u n icipal
solid waste. Waste Managem en t (2017), h ttp://dx.doi.org/10.1016/j.w asm an.2017.08.046
developed coun tries has less m oist ure con ten t, for e.g., in USA and
European coun tries it var ies from 20 to 30% as com pared to 50 to
70% in developin g coun tries such as in China and India (Cheng
et al., 2007; Mohee and Mudhoo, 2012). How ever, the w aste
st ream of developed count ries has high calorific values (2000–
4000 kcal/kg) as com pared t o the develop ing coun tries (700–
1600 kcal/kg) due t o the presence of high percen tage of paper
and other dry organ ic wast es (Patum saw ad and Cliffe, 2002). The
calor ific valu es of MSW stream of som e of the coun tr ies are show n
in Table 3 . In high incom e group count rie s, the decom posable
organ ic fract ion in their MSW stream is less and t he fract ion of
plast ics, paper, text iles and other recyclable w astes is m ore. The
organ ic conten t in MSW is below 30% (by w eigh t) in developed
count ries such as Japan, USA, Singapore and South Korea, but the
sam e in developing coun tr ies such as China , Sri Lanka, Pakistan ,
and India is m ore than 50%(Aleluia and Ferrão, 2016).
3. Heat ing values of m unicipal sol id waste
One of the im portant param ete rs for det erm inat ion of energy
con tent of MSW is t he heat ing value or the calorific va lue. There -
fore, it is necessary t o have reliab le and accurate heat ing valu e data
of MSW com ponent s for efficien t design and successful operat ion
and m aint enance of a WTE facilit y (Sh i et al., 2016). A m ajor prob-
lem is the inconsistencies in report ing the energy con tent of MSW.
Generally, the repor ted studies described the energy cont en t in
term s of h igher h eat ing value (HHV), low er heat ing value (LHV),
calor ific va lue, net heating value , gross heat ing value (Kathiravale
et al., 2003; Gonzá lez et al., 2001). Although these values are
inter-relat ed, but th is inconsistency causes confusion to t he read -
ers in com paring the resu lts. The ca lorific value is norm ally classi-
fied into HHV and LHV. LHV is the energy cont en t ava ilable from
com plete com bustion and does not consider the latent heat of
vapor isa tion of m oistu re presen t in w aste st ream . Whereas, HHV
is the theoretical m axim um energy con tent in w hich laten t hea t
of vaporisation of w astes is taken into consideration and is gener -
ally m easu red w ith t he help of a bom b calorim e ter and som et imes
with the help of equat ions, w h ich is a funct ion of u ltim ate analysis
of the subst rate (Kom ilis et al., 2012). How ever, the m easu rem ents
of heating va lue using bom b calorim e ter is tedious, requ ires skilled
operator and all MSW m anagem ent (MSWM) facilit ies are not
alw ays equipped w ith bom b ca lor im eter (Kat hiravale et a l.,
2003). The m ost com m only used equation in t heoret ical estim at ion
of heat ing value is Dulong equat ion (Ka th iravale et al., 2003),
wh ich w as originally developed for est im ation of heating value of
coal and m ay n ot be applicable for the estim at ion of heating value
of MSW (Shi et al., 2016). LHV calcu lat ion is based on the HHV and
moisture con tent of feedstock (Abu-Qudais and Abu -Qdais, 2000;
Komilis et a l., 2012). LHV has more practical app lications t han
HHV and it is la rgely used in energy est im at ion , as th is is the
energy that is actua lly used in elect ricity generat ion from a MSW
incinera tor (Kom ilis et al., 2014).
4. Waste to energy opt ions
The aim s of any w aste m anagem en t system are m aterial and
energy recovery, followed by disposal of t he residues. Bu t, an op ti-
m al choice for a w aste p rocessing technology is not on ly subject to
econom ic requ irem en ts, energy recovery or w aste dest ruction abil-
it y, bu t also to look for environm en tal regula tory com pliance
requ irem en ts of the concerned area. Therefore, it is necessa ry to
select the best ava ilable technology for waste processing, w hich
fu lfi ls all the required criteria for a successful operation (Ali
et al., 2010). A variety of w aste conversion processes are availab le,
in w hich the t hree m ost w idely used technologies a re (Kalyan i and
Pandey, 2014): (i) therm al conversion [(incine rat ion, pyrolysis,
gasificat ion , p roduction of energy from refuse derived fuel (RDF)],
(ii) biological con version (anaerob ic d igest ion /biomethanation
and com post ing), an d (iii) landfilling w ith gas recovery. The
MSW treatm ent techniques along w ith the typical react ion prod-
ucts are show n in Fig. 3.
4.1. Thermal conversion technologies
Therm al conversion involves thermal t rea tm ent of organ ic m at-
te r p resent in MSW t o produce either heat energy, fuel oil or gas.
Therm al conversion technology is generally usefu l for dry w aste
(low m oistu re con tent ) w ith high percentage of non-
biodegradable organ ic m at ter . Som et im es, therm al conversion
technology is applied to RDF, w hich is a com bust ible m ater ial w ith
h igh calorific value. For product ion of RDF, t he recyclable and non-
com bust ible m at erials are removed from MSW follow ed by shred-
d ing and /or pellet isat ion of the rem ain ing w aste . Incineration,
w hich is a controlled com bust ion of w astes a t high tem peratu re
is the most w idely used m ethod in t herm al conversion t echnology
(Shi et al., 2016). The other th erm al conversion technologies
(pyrolysis and gasificat ion ) are still in resea rch phase and they
are not feasible for com m ercial pu rpose a t large scale, m ay be
due to lack of proper MSW characterisat ion dat a, poor feedstock
qua lity and inappropriate design of the facilit y (Appels et al.,
2011; Sh i et al., 2016). There are very few com m ercially operat ing
pyrolysis/gasifica tion plan ts across th e w orld for t reat ing MSW.
These plants operate for treat ing MSW along w ith som e other type
of w astes such as indust rial w aste, biom edical w ast e, biom ass, etc.
(Ion escu et al., 2013). The typ ical react ion cond it ions and products
from therm al t reatm ent processes are show n in Table 4. The main
d ifferences am on g these th ree t herm al t reatm en t processes are the
atm ospheric con dit ion (i.e., p resence of oxygen) and t he operat ing
tem perature. The qualit y of t he final products and the usefu l inter-
m ed iate products depends m ain ly on these tw o param eters. Oper-
at ing tem peratu re of therm al processes la rgely depends on the
process design and feedstock m ater ials. For incineration process,
p re- treat m ent of MSW is genera lly not practiced in developing
countr ies; raw MSW is directly used as a feedstock m at erials.
Table 3
Calorific valu e of MSW of developed and developing coun tries.
Countr ies Calor ific value (kcal/kg) References
Developing Bangladesh (717) Hossain et al. (2014)
China (1200–1600) Zhou et al. (2014)
In dia (800–1100) Unnikrishnan and Singh (2010)
Malaysia (1500–2600) Kathirvale et al. (2004)
Sri Lanka (950–1250) Reddy (2011)
Thailand (500–1500) Reddy (2011)
Developed Japan (2000–2200) Hla and Roberts (2015)
S. Korea (2600–3000) Yi et al. (2011)
UK (2200–3000) Hla and Roberts (2015)
A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx 5
Please cite this article in press as: Kum ar, A., Sam adder, S.R. A review on tech nological op tions of w aste to energy for effective m anagement of m u nicipal
solid w aste. Waste Managem ent (2017), http://dx.doi.org/10.1016 /j.w asm an.2017.08.04 6
4.1.1. Incineration
In itially t he incinerators w ere used for volum e reduction and
protect ing the m en and environm ent from the hazardous w astes,
bu t not for energy recovery (Brunner and Rechberge r, 2015). After
advances in a ir pollu tion control technologies, incinerat ion is now
considered as an att ract ive w ast e treatm ent opt ion, especially in
the developed coun tries (Psom opoulos et al., 2009; Ouda et al.,
2016). Scarlat et al. (2015) report ed that incine rat ion is one of
the m ost com m on waste d isposal t echniques in the developed
count rie s (EU, US and Japan) due to the st ringen t w aste-related
regu lations on w aste d isposal using landfilling. The em ission s from
waste incine rators have been reduced to such an exten t that in
2003, t he United Stat es Environm ental Protect ion Agency (US
EPA) declared incine rat ion of MSW as a cleaner source of energy
(Lem e et al., 2014). Incineration is the m ost com m on w aste treat -
m ent techniques in w hich, the w ast e m ass and volu me can be
reduced by 70% and 90% respect ively (Chen g and Hu, 2010;
Nixon et al., 2013a,b; Gohlke and Mart in, 2007; Lombardi et al.,
2015); at the sam e t im e, heat and/or e lectricity can a lso be pro-
duced (Singh et al., 2011). From incinerators, heat is supp lied if
the re is a requ irem ent for dist rict heating (in cold coun tr ies),
som etim es it is supplied to the indust ries like paper m ill, and elec-
t ricity is produced in all the other cases (Brunner and Rech berger,
2015). But in a few recent stud ies (Meylan and Spoerri, 2014;
Allegrini et al., 2014), the scien t ist s h ighligh ted som e other advan-
tages of incinerat ion apart from volum e reduct ion and elect ricity
genera tion such as, ut ilisat ion of bot tom and fly ash of incineration
p lan ts in road const ruct ion & cem en t product ion and recovery of
fe rrous and non-ferrous subst ances. Thus, fu rt her technological
developm en t in m eta l recovery from dry bot tom ash of in cinera-
t ion p lan ts w ill enhance the accep tance of WTE facilitie s (Morf
et al., 2013). Bu t in the developing coun tries, the incinerat ion is
considered as the m ost reliable and econom ical w hen it is used
for mass burn ing w ithout p re -t reatm en t of MSW for elect ricity
genera tion. Incinerat ion generally t akes place at d ifferent stages
depend ing upon the operat ing condit ions and t ype of w astes incin-
erat ed (Table 5). One of the m ain advan tages of MSW incineration
is the com plet e dest ruct ion of any living organ ism s and m inerali-
sat ion of organic substances into harm less end products (Brunner
an d Rechberger, 2015).
MSW com posit ion and characterist ics are highly heteroge-
neous, th us they m ust be evaluated before designing any WTE
Table 4
Typical reaction condit ions and products from thermal treatment processes.
Parameters Incineration Pyrolysis Gasification
Princip le Full oxidat ive com bust ion Therm al degradation of organic mater ial in the absence
of oxygen
Partial oxidation
Operat ing tem perature
(°C)
850–1200 400–800 800–1600
Atmosphere Presence of sufficien t oxygen Absence of oxygen Controlled supply of oxygen
Reaction
products
Solid Bottom ash , fly ash, slag, other non-
combustible
substances like m etals and glass
Ash , char (combination of non-combustible and carbon) Ash , slag
Liqu id Con densate of pyrolysis gas (pyrolysis oil, wax, tar)
Gas CO2, H2O, O2, N2 Pyrolysis gas (H2, CO, hydrocarbons, H2O, N2) Syngas (H2, CO, CO2, CH4, H2O, N2)
Pre- treatm ent Not necessary Required Required
Raw MSW Usually preferred Usu ally not preferred Usually not preferred
Biogas Landfill gas
Bio-fuel
Compost Soil conditioner
Biological conversionThermal conversion
Municipal Solid Waste
Landfilling
Incineration Gasification Pyrolysis
Slow 
Pyrolysis
Fast 
Pyrolysis
Aerobic Composting Anaerobic Digestion
Energy/ElectricityHeat/
Steam
SyngasInert 
residue
Fig. 3. Municipal solid waste treatment techniques and their products.
6 A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx
Please cit e this article in press as: Ku m ar, A., Sam add er, S.R. A review on tech nological options of wast e to energy for e ffective managem ent of m u n icipal
solid waste. Waste Managem en t (2017), h ttp://dx.doi.org/10.1016/j.w asm an.2017.08.046
facility (Turcon i et al., 2011). Tan e t al. (2014) suggested t hat ,
incinera tion is su itable for com bust ible non-biodegradable MSW
with low m oistu re conten t. Som et im es auxiliary fue ls are used
along w ith MSW during incineration , but it is worth t o not e tha t
the use of auxiliary fuels along w ith MSW is not requ ired w hen
the LHV of wast e is bet w een 1000 kcal/kg and 1700 kcal/kg or
above (Chen an d Christensen, 2010; Kom ilis et al., 2014). Accord -
ing to t he World Bank report , the average calorific value of MSW
should be at least 1700 kcal/kg (World Bank, 1999) for an effective
incinera tion operation with energy recovery, w hereas, accordingto
Internat ional Energy Agency, the values m ust be greater t han
1900 kcal/kg for t he incine rat ion operat ion to be feasible
(Melikoglu , 2013). It is apparent that the presence of inert w ast e
and m oist ure con tent reduces the calorific value an d affects the
com bust ibility of MSW, w hich directly affects t he perform ance of
an incinerator. As t he m oistu re con ten t increases in the w ast e
st ream , it s calorific va lue star ts decreasing du e to lat en t heat of
vapor isa tion . There fore, som et im es pre-t reatm ent (therm al,
mech an ical, chem ical and biologica l) of w astes are done to rem ove
the excess m oistu re conten t, inert wast e and toxic elements such
as ch lorine and m ercury (Lom bardi et al., 2015). A typical inciner -
ator gen erates 544 kWh of energy and 180 kg of solid residue per
tonne of MSW incinerated (Zam an, 2010).
4.1.1.1. Incinera tion in developed and developing countries. Modern
MSW incinerat ion p lan ts operate quit e well for recovering energy
in the form of steam for elect ricity generat ion in cit ies of industr i-
alised nations (Psom opou los et al., 2009). Less annual cap ita l cost ,
operational cost, bet ter skill of the operators, higher daily through-
pu t (Psom opou los et al., 2009), and high calorific value of the MSW
altogether m ade incinerat ion a m ore a tt ract ive than other WTE
technologies for the citie s of developed coun tries. In Asian coun-
trie s, Japan is part icularly fam ous for w aste incineration technol-
ogy due to str ingen t regulation and lim it ed land area for w aste
dum ping. Incinera tion of MSW is done w idely in d ifferent Western
European coun tries ranging from 35% to as m uch as 80% of the
total w aste generat ed (Reddy, 2011). Other European count ries
also rely significan tly on incineration for handling m unicipal
waste . The North -eastern US recovers energy from m ore t han
40% of its tota l solid w aste genera ted using incinerat ion only.
Incineration is not feasib le for m any deve lop ing countries excep t
those w ith fast grow ing econom ies (su ch as China, Malaysia,
etc.), du e to (a) the h igh capital, operating and main tenance cost s,
(b) un favourable characteristics and com posit ion of w astes, (c) lack
of techn ical exper tise in the field , and (d ) availability of com para-
tively low cost land for wast e d isposal. But , China had gone for
huge expansion in MSW in cinerat ion in the past decade and is
expected to reach up to 500,000 t on nes/d by 2020 (Lu et al., in
press). Li e t al. (2015) reported t hat , t ill 2013 Ch ina had 166 oper-
ational incineration plants for generat ion of electr icity using MSW
at the rate of 166,000 t on nes/d . Cheng and Hu (2010) claim ed tha t
th e waste incinerat ion had m ore con tribu tion to the overall renew-
able energy generat ion in China. Bu t Lom bardi et al. (2015)
reported that Ch ina is facing several problem s in MSW incineration
due to poor w aste feedstock quality, incom ple te com bust ion , and
increased air pollu t ion. High m oistu re conten t, var iable com posi-
tion and low energy con ten t are som e other m ajor d ifficu lt ies faced
in incinerat ing w astes in developing coun tries (Reddy, 2011).
4.1.2. Pyrolysis
Pyrolysis is an advanced therm al t reatm ent m ethod . It takes
p lace in t he temperature range of 400–800 °C in absence of oxygen.
It p roduces pyrolysis gas, oil and char, w hose yield and qu ality
m ainly depend upon the heat ing rate, process t em pera tu re, resi-
dence tim e (Lom bardi et al., 2015), com posit ion of w astes, and par-
ticle size of the waste (Ka lyani and Pandey, 2014). At low er
tem perature (500–550 °C), pyrolysis oil, w ax and ta r a re the m ajor
p roducts, and at higher tem peratu re (>700 °C), pyrolysis gases are
th e m ajor p roducts. For good qua lity pyrolysis products, the feed-
stock should be of specific type of w astes (plast ic, tyre, elect ron ic
equ ipm ent , electric w aste, w ood wast e, etc.). Pyrolysis of specific
type of w astes was repor ted in various previous studies, w hich
focussed on the process it self rather than the possible com m ercial
use of pyrolysis product s. In part icular, pyrolysis has received spe-
cial at ten t ion recen tly for recycling of scrap t yres for recovery of
oil, wire, carbon black and gas (Lom bardi et al., 2015). As, it is evi-
den t that pyrolysis pe rform s w ell in treat ing specific w aste stream ,
but ve ry lim it ed studies have been reported abou t energy recovery
from MSW using pyrolysis at com m ercial scale. A plan t of 110 ton-
nes/d capacity in Burgau , Germ any has been successfully generat-
ing elect ricity th rough MSW pyrolysis since 1987 (Lom bardi et al.,
2015). Panepinto et al. (2014) reported abou t som e ot her success-
fu lly operat ing MSW pyrolysis plants such as in Ham m , Germ any
(275 tonnes/d ), Toyohash i, Japan (295 tonnes/d ), UK (22 tonnes/
d ), and France (191 tonnes/d). Baggio et al. (2008) reported that
pyrolysis of MSW for product ion of gas can be used for energy
recovery using Gas Turbines w it h a net conversion efficiency of
28–30%.
4.1.3. Gasification
Gasificat ion is another therm al conversion t echnology, in w hich
organic com pou nd ge ts converted in to syngas in cont rolled atm o-
sphere of oxygen at h igh tem perature. Syngas is the m ain product
of gasificat ion process, w hich can be used to produce energy
th rough com bustion. It can a lso be used to produce feedstock for
chem icals an d liquid fuel (Yap and Nixon , 2015). Most of the
reported gasifica tion stud ies are focussed on hom ogeneous flow
of solid fuel (coa l, w ood , etc.) and specific t ype of MSW. Gasifica-
tion has been widely used in coal industry, but recently it has been
considered as a potent ial energy recovery op tion from MSW
(Arafat and Jijakli, 2013). Panep in to et al. (2014) invest igated 100
p lan ts around the w orld that use gasificat ion t echn ique to process
Table 5
Stages of incineration process.
S. No. Steps References
1 Drying and degassing
Pyrolysis and gasification
Oxidation
Tabasová et al. (2012)
2 Incineration
Energy recovery
Air pollu tion cont rol
Lee et al. (2007) and Zheng et al. (2014)
3 Waste delivery and storage section (bunker)
Waste com bustion section (furnace)
Energy recovery and conversion section
Flue gas cleaning section
Branchin i (2015)
A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx 7
Please cite this article in press as: Kum ar, A., Sam adder, S.R. A review on tech nological op tions of w aste to energy for effective m anagement of m u nicipal
solid w aste. Waste Managem ent (2017), http://dx.doi.org/10.1016 /j.w asm an.2017.08.04 6
MSW. MSW gasifica tion technology is w idely used in Japan, wh ere
85 plan ts w ere operat ing till 2007. In othe r coun tries (such as in
USA, UK, Italy, Germ any, Norw ay and Iceland), gasification has
been used to process MSW at sm aller scale (Panepin to et al.,
2014). It has been reported that gasificat ion process generates less
CO2 t han the incinerator of sim ilar capacity (Murphy and McKeogh ,
2004). Defra (2013) repor ted t hat , m odern gasificat ion un its com e
with enclosu res, w h ich effect ively reduce the ch ance of w at er and
soil con tam inat ion. Asia has seen a huge leap in the gasificat ion
technology in last few years and can be considered as one of the
m ost favourable m arkets for gasificat ion t echnology follow ed by
Europe, Africa and USA (Ouda et al., 2016).
Zam an (2010) repor ted th at pyrolysis and gasificat ion technolo-
gies a re m ore favourab le than the incinerat ion technology for MSW
from environm en tal im pact an d energy recovery prospect ive .
Pyrolysis and gasificat ion technologies can reduce t he w ast e vol-
um e by 95% and require less intensive flue gas cleaning as com -
pared to incineration (Yap and Nixon, 2015). Pyrolysis and
gasificat ion t echniqu es are bet ter t han other WTE options in view
of environm ent al em issions and energy recovery efficiency. How -
ever, they are yet to be established at large scale across t he w orld
(predom inan t ly in developing coun tries) for energy recovery from
MSW (Luz et al., 2015) due to poor efficiency of gasifiers and gas
clean ing syst em s, heterogeneity in MSW com position & part icle
size, and h igh m oisture con ten t.
4.2. Biologica l conversion technology
Biological conversion technology is based on m icrobial decom -
position of the organ ic content of MSW. Many researchers reported
this t echnology as environm ent ally suitable for energy recovery
from w astes (Pan t e t al., 2010). It is genera lly p referred for the
wastes w ith h igh percent age of organ ic b iodegradable m atter
(pu trescible) and high m oistu re conten t. The m ain technologica l
op t ion for energy recovery under th is category is anaerobic diges-
tion or biom ethanat ion .
4.2.1. Anaerobic digestion
Anaerobic d igestion (or biom ethanat ion ) is a p rocess of m icro-
bial degrada tion of organic b iodegradable m at ter in absence of
oxygen that produces biogas and stab ilises the sludge. The quality
of the generated biogas depends on the process param eters and
subst rat e com posit ion ; the biogas is typically com posed of 50–
75% CH4, 25–50% CO2 and 1–15% of ot her gases (such as, w ater
vapour, NH3, H2S, etc.) (Surendra et al., 2014). The produced
slu rry/sludge can be used as a soil condit ioner and /or as an organ ic
am endm ent in agricu ltu ral field (Pivato et al., 2016; Tam bone
et al., 2009). Anaerobic d igest ion is u sed to recover both nu tr ien t
and energy from biodegradable w ast e. Ali e t a l. (2016) reported
tha t, the quality (as a fert iliser) of solid p roducts of anaerobic
digestion depends m ain ly on the quality of feedst ock (proteins,
m inerals and vitam ins con tent of w aste). Brown e et a l. (2014)
reported that European legislation prohibit ed the use of solid prod-
ucts of anaerobic digest ion as a fert iliser, due to the presence of
undesirable m aterials in feedst ock. In anaerobic d igestion, the
organ ic fract ion of the biodegradable MSW gets degraded and con-
verted into m ethane th rough a series of stages. The init ial st age is
called hydrolysis, in w hich t he com plex organic com pounds of
MSW like carbohydrates, proteins and fats ge t con vert ed in to sol-
uble organ ic m aterials such as sugars, am ino and fa tty acids. Fer-
m entation is the next stage of anaerobic digest ion process in
which the organic m olecules break into acet ic acid, H2 and CO2.
The final stage is m ethanogenesis, in w hich m ethane form at ion
takes p lace. The detailed process flow for conversion of organ ic
m atter into methane is show n in Fig. 4 . The anaerobic digest ion
processes are m ainly of tw o types, ‘‘wet” (10–15% of dry m atter
conten t), and ‘‘dry” (24–40% of dry m at ter conten t) processes
(Lun ing et al., 2003). Wet process produces m ore liquid w aste
an d less solid product . The requ ired volum e of react or for w et pro-
cess is less t han that of the dry process. The type of reactors (single
st age or m ult i stage), p rocesses (wet or dry) and m ethane yield
depend on t he region , quality of feedstock and the produ ct
requ irem en ts.
It has been estim ated that anaerobic d igest ion can produce 2–
4 tim es m ore methane per tonne of MSW in 3 w eeks than that of
a landfill in 6–7 years (Ahsan , 1999; Saxena et al., 2009). Murphy
et al. (2004) report ed that 1 m 3 of biogas produced from anaerobic
d igestion process can genera te 2.04 kWh of elect ricity taking con-
version efficiency of 35%. Abou t 150 kg of m ethane can be gener-
at ed from anaerobic d igestion of 1 tonne of MSW considering
60% organ ic m at ter and 40% m oistu re (Scar lat e t al., 2015). How-
ever, t he m ajor problem associat ed w ith th is process is the long
dura tion (t yp ically 20–40 days) of m icrobial react ion (Pham
et al., 2015). Som et im es, presence of nit rogen rich com ponen ts
an d cat ions (such as sod ium , potassium , and calcium ) in the w aste
st ream increases am m onia and salt concen trations (Fount ou lakis
et a l., 2008 ; Chen et al., 2008) that m akes the process toxic for
m et hanogenic act ivit ies. Several stud ies (Gom ez e t al., 2006;
Cristancho and Arellano, 2006) suggested co-d igest ion of MSW
w ith low nitrogen con tent w aste, sew age sludge, and food w aste
to reduce the h igh am m onia con centrat ions an d to increase t he
b iogas yield of the process. The m ethane yield of organ ic fraction
of MSW un der different operat ing condit ions repor ted by various
researchers is sum m arised in Table 6. Most of the researchers used
food w astes along w ith the su itable inoculum for m axim um gas
recovery. The quality of the biogas generat ed using anaerobic
d igestion technology can be im proved by rem oving CO2 and other
t race gases for use as a t ranspor tat ion fuel called biom et hane. Th is
can subst itute natural gas in variety of dom est ic and industr ial
app licat ions (Kastu rirangan, 2014; Appe ls et al., 2008). Earlier,
an aerobic d igest ion w as used for t reatm en t of dom est ic sew age,
agricu ltu ral w aste, organic w aste and an im al m anure, bu t now it
is extensively used for energy recovery from MSW especially in
the developing countries, wh ere w astes have h igh m oistu re con-
tent (Yap and Nixon , 2015). Abbas et al. (2017) and Ali et al.
(2013a,b) evaluated t he feasibilit y of biogas recovery and found
that the biogas recovered from anaerobic digest ion t echnology is
econom ically and environm entally sustainable.
4.3. Landfilling
San itary landfilling is defined as the con trolled d isposal of
w astes on land t o reduce t he negat ive im pact on the environm ent
th rough biogas recovery and leachate m anagement (Fig. 5). How-
ever, unsan itary landfilling offers a sim ple r and affordable solution
Soluble 
H2, CO2 Acetic acid
Volatile fatty acids 
CH4 + CO2 
Hydrolysis
Acetogenesis
Acidogenesis
Methanogenesis Methanogenesis
Organic matter
Fig. 4. Stages in anaerobic digestion process.
8 A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx
Please cit e this article in press as: Ku m ar, A., Sam add er, S.R. A review on tech nological options of wast e to energy for e ffective managem ent of m u n icipal
solid waste. Waste Managem en t (2017), h ttp://dx.doi.org/10.1016/j.w asm an.2017.08.046
for disposal of the increasing w aste quan t ity and is the m ost com -
mon pract ice in developing coun trie s, that poses a ser ious th rea t to
the environm en t (Wang and Geng, 2015). Previous st ud ies show ed
that landfilling causes the h ighest environm en tal im pact com pared
to other w aste managem ent op tions (Cherubini et al., 2009; Em ery
et al., 2007; Marchett ini et al., 2007 ; ISWA, 2012). It has been
reported t hat m ost of the cit ies of developing coun tr ies, t he w aste
is disposed on low lying areas loca ted at the outskirts of the cit y
(Talyan et al., 2008 ; Kum ar and Chakrabarti, 2010). When the fac-
tors such as environm enta l im pact , health im pact , land degrada-
tion , and groundw at er cont am inat ion are conside red , landfi lling
becom es the w orst op tion. How ever, developed coun tries have
started to discourage landfilling of w astes t hrough str ingen t regu-
lat ions, w aste reduct ion and recycling. The landfi ll leachate (a dark
effluen t of unusually variable com posit ion with recalcit ran t com -
pounds) is a m ajor polluting substance released from landfi lls or
Table 6
Methane yield during anaerobic digestion of MSW.
References Feedstock
m ater ial
Sam pling
area
Type of
reactor
Operating condit ions Inocu lum Methane
yield
Observations/rem arks
Zhang et al. (2007) Food waste
from
restauran ts,
hotels and
grocerystore
San
Francisco,
California
Batch (1 L) Avg. moisture content and
Volatile Solids/Total Solids
(VS/TS) was 70%and 83%
respectively, t emperature
w as therm oph ilic
(50 ± 2 °C). The reactor was
m onitored for 28 days
Sludge from
w astewater
treatment
plant
435 mL
CH4/g of
VS
Samples of w eekends w ere not
t aken for the an alysis. Sam ples
w ere taken from the w aste
m an agement com pany (responsible
for w aste collect ion). Thus, direct
sampling from the source of
generation could have reduced the
contamination of food waste from
other types of w astes and the
m ethane yield might have
increased.
Macias-Corral et al.
(2008)
Organic
fraction of
MSW
(OFMSW)
New
Mexico,
USA
Batch Avg. VS was 82%,
temperature w as
therm ophilic (55 °C)
Supernatan t
from
anaerobic
w astewater
treatment
plant
37 mL
CH4/g of
dry waste
Samples w ere taken from kerbside
collection truck and then
segregated in to organic fract ion
w hich might have reduced the
quality of the samples. The OFMSW
contains main ly paper waste (70%).
Yong et al. (2015) Food waste
and straw
Beijing,
China
Batch (1 L) Organic loading w as 5 g VS/
L, perform ed at mesophilic
temperature (35 °C)
Anaerob ic
granular
sludge from
starch
processing
w aste w ater
0.392 m 3
CH4/kg of
VS
The methane yield has been
increased by 39.5%and 149.7%
compared with individual digest ion
resu lts of food waste and straw
respect ively. The carbon to nitrogen
(C/N) ratio for optim um digestion
should be in range of 25–30. But the
C/N rat io of food w aste and straw
w as 28.4 and 43 .4 respectively and
thus the C/N rat io of m ixed waste
w as on slight ly h igher side of
optimum values.
Scano et al. (2014) Fru it and
vegetable
wastes
Sardin ia,
Italy
Continuous
(1.13 m 3)
The reactor was monitored
for 174 days and
m ain tained at mesophilic
conditions (35 ± 0.5 °C)
Digestat e of
pig m an ure
0.43 Nm 3
CH4/kg of
VS
Fruit w astes have h igh sugar
conten t w hich increases the CO2
concen trat ion in the biogas and
reduces the CH4 yield. Thus,
optimum loading rate of substrates
is very much essen tial.
Kom emoto et al. (2009) Food waste Saitama,
Japan
Batch (2 L) TS and VS of the sam pled
w aste w as 16%and 94%
respectively. The
experim ent w as performed
at six d ifferen t temp. 15 °C,
25 °C, 35 °C, 45 °C, 55 °C
and 65 °C
No inoculum 64.7 mL
CH4/g of
VS
Biogas production w as found more
at mesophilic conditions (35 °C and
45 °C) than the thermophilic, which
is contrary to the findings of several
p revious researches. But at
thermophilic condit ion the HRT is
less which will effectively reduce
the reactor size.
Haider et al. (2015) Food waste
and rice
husk
Islam abad
and
Faisalabad,
Pakist an
Batch (1 L) TS of food waste and rice
h usk w as 24%and 90%
resp ., w hereas VS was 92%
and 81%resp. The reactor
w as monitored for 45 days
at m esophilic conditions
(37 ± 1 °C)
Acclimatised
cow dung
584 mL
biogas/g
of VS
Food w aste and rice husk were
m ixed in d ifferent ratios to get the
desired level of C/N rat io. Cow dung
as inoculum reduces the
accumulat ion of VFA, thus protects
d igester from failure. Purity of the
b iogas was not mentioned .
Ma et al. (2011) Kitchen
waste
Belgium Batch
(1.2 L)
TS and VS of waste was
166 g/kg and 155 g/kg resp.
The reactor operated at
therm ophilic condit ions
(55 ± 2 °C)
Sludge from
potato w aste
treatment
plant
520 mL
biogas/g
of COD
Different pre- treatment techniques
(acid, thermal, thermo-acid,
p ressure-depressure, freeze-thaw)
w ere applied to the kit chen waste
and were found that the b iogas
yield im proved w ith the pre-
t reated kit chen waste as com pared
to the raw kit chen w aste. However ,
the process is not feasible in the
develop ing countries due to less
conversion efficiency of biogas to
energy, m aking the process cost ly.
A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx 9
Please cite this article in press as: Kum ar, A., Sam adder, S.R. A review on tech nological op tions of w aste to energy for effective m anagement of m u nicipal
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dum psites (Mü ller e t al., 2015) that pollu tes the nearby sur face
water courses and groundwater aqu ifers. Accord ing to experts,
on ly 10–15%of the t ot al w aste generated should go for landfilling
and it should be the last op t ion for citie s w h ere land is lim ited .
4.3.1. Modelling landfill gas generation
The organ ic m att er present in the deposit ed w astes in landfills
undergoes com plex biological and chem ical decom posit ion t hat
result s in the product ion of landfill gas (LFG). The degradat ion of
organ ic m at ter in to LFG occurs in five differen t phases (Noor
et al., 2013). The first phase is hydrolysis/aerob ic degradat ion , in
which t he aerobic bacteria breaks com plex organic m at ter int o
CO2 and H2O. The second phase is hydrolysis and ferm en tat ion ,
in w hich the soluble organ ic com ponent s are decom posed int o
CO2, H2, NH3 and organ ic acids in p resence of facu ltat ive bacteria .
The third phase is acidogenesis/ace togenesis, in w hich the organ ic
acids produced during second phase get convert ed in to acetic acid ,
form ic acid, alcoh ols, H2 and CO2 by anaerobic bacteria. In the
fou rth phase (m ethan ogenesis), the m ethanogen ic bacte ria con-
sum es the product of t he th ird phase and produces p rimarily
CH4, CO2, as w ell as oth er t race gases in sm aller am oun t. The fina l
phase is oxidat ion , in w h ich CH4 gets conver ted in to CO2 and H2O
under aerobic condition. The LFG production rate inside a landfill
depends on various factors, such as, type of landfill, w aste com po-
sition , clim atic cond ition (tem peratu re and precipitat ion ), m ois-
ture con tent , and w aste age (Scarlat et a l., 2015). LFG conta ins
50–60% m ethan e (Unn ikrishnan and Singh, 2010) and is consid -
ered as one of the m ajor source of an th ropogenic m ethane em is-
sions. As per an est ima te, 30–70 m illion tonnes of m ethane gas is
em itt ed per year from w aste landfi lls (Johari et al., 2012). There-
fore, recovery of m ethane from a landfill for elect ricity generat ion
or other use is necessary t o reduce t he em ission. Som et imes, recov-
ery of LFG is techn ically not feasible, in tha t case on-site flaring of
LFG is done. Bu t , for this it is necessary to get t he estim a tes of
trapped LFG inside a landfill. The recom m ended approach involves
m odelling of LFG gen erat ion . There are various m odels ava ilable t o
predict the m ethane em issions from landfills. Som e of t he m ost
widely used m odels (seven m odels) are descr ibed in Tab le 7. How -
ever, differen t em ission m odels give differen t results for a single
landfi ll and the m odels give accura te resu lts for t he region it has
been deve loped , as t he w ast e com posit ion differs across the coun-
tries. Ou t of the seven m odels, six m odels are based on the Euro-
pean scenario and one on the USA scenario. These m odels have
great ly reduced the t ediou s m easurem en t techn iques generally
app lied for m et hane estim at ion from landfi lls. Although , TNO-
m odel w as developed for the w aste character ist ics of Netherlan d,
but th is can be used for the est im at ion of LFG for other coun tr ies
also as it has less relat ive error (22%) be tw een observed and calcu-
la ted values. In a st udy, it w as estim a ted t hat 1 tonne of MSW gen-
erat es 80 m 3 of LFG and China alone m ay cont ribute 10 billion m 3
LFG to the global LFG em issions in 2020 (Qu et al., 2009).
5. Energy r ecovery poten t ial and econom ics of WTE
technologies
At present, Ch ina generates abou t 300 m illion t onnes of w aste
an nually (World Energy Resources, 2016) andthe wast e con tains
h igh propor tion of food waste of low ca lor ific value and h igh m ois-
tu re cont en t sim ilar t o tha t of other deve loping coun tries. There-
fore , the convent ional in cinerat ion plants used in developed
coun tr ies are expected t o perform poorly in such condit ion s. Thus,
China has developed new circu lat ing fluidised bed based in cinera-
t ion plan ts to coun ter this p roblem and curren t ly 28 such p lan ts
are successfully generat ing electr icity by processing 800 tonnes/d
of MSW (World Energy Resources, 2016 ; Zhao et al., 2016).
Cheng et al. (2007) report ed that the grate based circu lat ing flu-
id ised bed incinerator is w ell su ited for MSW w ith h igh m oistu re
an d low energy con ten t . A wast e incinerat ion plant in Eth iop ia
w ith capacity of 50 MW (the fir st WTE facility in Sub-Saharan
Africa) is expected to be com m issioned in 2017 , w hich w ill process
350,000 t onnes of w aste per yea r. However, the p lan t m ay struggle
for it s operational cost due to m any issues such as low calorific
valu e of incom ing MSW stream , lack of local techn ical expertise,
an d low energy prices (World Energy Resources, 2016).
Perkou lidis et a l. (2010) reported that a WTE facilit y in Central
Greece w as expected to recover 0.55 MW elect ricity pe r t on ne of
MSW, with net conversion efficiency of 22.5%. As per the estim a te,
Malaysia is expected t o generate 2.63 109 kWh of elect ricity
from LFG alone by the year 2020, w hich w ill generate revenues
w or th of US$ 262 m illion for Malaysia (Noor et al., 2013). The
en ergy recovery potent ial of five anaerob ic digest ion plan ts of
Greece Municipalit y w as found to be 695 kWh/tonne w ith an aver-
age operat ing cost of 84 US$/ tonne (Karagiann idis and Perkou lid is,
2009). Brazil has a poten tial of generat ing approxim ately 660 MW
electricity per day from MSW landfills alone. The presen t study
review ed m ore than 100 published art icles from 2010 to 2017 on
WTE technologies, ou t of which t he crit ical observat ion on som e
of the recen t lite rat ure on WTE technologica l op tions across
Fig. 5. A typical engineered landfill with biogas recovery system. Source: Zaman, 2010.
10 A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx
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solid waste. Waste Managem en t (2017), h ttp://dx.doi.org/10.1016/j.w asm an.2017.08.046
Table 7
Description of m ethane generation potential m odels.
Models Formula Model descrip tion Rem arks
IPCC-m odel
(IPCC, 2006)
Q ¼
P T 1
x¼S f MSWTx MSWFx L0 ;xðe kðT x 1Þ e kðT xÞÞg R
h i
ð1 OXÞ
where,
L0 = m ethane generat ion poten tial (Gg of CH4/Gg of waste)
= 1.33 F DOC DOCF
F = fraction by volum e of CH4 in landfill gas
DOC = amount of degradab le organ ic carbon (Gg C/Gg MSW)
DOCF = fract ion of DOC decomposes
Q = m ethane emissions (Gg/year)
MSWT= total MSW generated (Gg/year)
MSWF = fraction of MSW landfilled
k = react ion constant (year-1)
T= inventory year for w hich emissions are calcu lated
x = year in which waste was landfilled
S = start year of in ventory calculation
R = recovered m ethane (in Gg/year)
OX= oxidat ion factor (fract ion)
First order decay model (the
IPCC-2006 revised equation).
It takes into account the rates of
w aste degradation and methane
generat ion over t ime.
Based on waste landfilled and
degradable organ ic fraction.
Emissions est im ations produced
by the model will allow
countries to assess the im pacts
of d ifferen t waste m anagem ent
and emission mitigation
practices.
It was basically developed for
the European count ries.
LandGEM
(US-EPA, 2001)
QCH4 ¼
P n
i¼1
P 1
j¼0:1 kL0ðMi=10Þðe
ktij Þ
where,
QCH4 = estim ated m ethane generation flow rate (m 3/year)
L0 = m ethane generat ion poten tial (m 3/tonne)
Mi = m ass of solid waste disposed in the ith year (tonne)
tij = age of the jth section of waste mass disposed in the ith year (decim al
years)
i = on e year time increm ent
n = (year of the calcu lat ion) (in itia l year of waste acceptance)
j = 0.1 year increment
k = m ethane generation rat e (year 1)
Microsoft Excel-based software
applicat ion developed by EPA
that uses a first-order decay rate
equation to calcu lat e estimates
for methane and LFG generation.
It assum es that methane
generat ion is at its peak shortly
after in itia l w aste placement
and rate of methane generation
then decreases exponentially as
organic mater ial is consum ed by
bacteria.
Based on US waste composit ion .
Inaccurate assum pt ions about
variables such as organic
conten t, fu tu re d isposal rates,
site closure dates and collect ion
efficiencies can resu lt in large
errors.
TNO-m odel
(Oonk and Boom ,
1995)
at ¼ 11:87AC0 k1 e k1 t
where,
at = landfill gas product ion at a given time (m 3/year)
1= dissim ilation factor 0.58
1.87 = conversion factor
A= am ount of waste (in tonne)
C0 = amount of organ ic carbon in waste (kg of C/ tonne of waste)
k1 = degradation rate constant 0.094 (year 1)
t = time elapsed since depositing (year)
First order model w hose
parameters were based on real
data of landfill gas generation .
Direct estim at ion of methane or
landfill gas.
Information on organic
com ponent of waste
com ponents are not available.
The model is validated by
emission measurem ent at 20
landfills across Netherlands and
was found that the mean
relative error between observed
and calculated landfill gas w as
22%.
It is one of the few m odel, where
the models data were validated
with the actual site landfill gas
measurement.
GasSim
(Gregory et al.,
2003)
Not available GasSim is a first order
m ult iphase m odel, w hich
quantifies all landfill gas relat ed
prob lems of a lan dfi ll, ranging
from m ethane emissions, effects
of ut ilisation of landfill gas on
local air quality to landfill gas
m igration via the subsoil to
adjacen t bu ild ings.
GasSim is based on UK w aste
stat istics.
Calculation modules in the
program are protected .
Afvalzorg
(Scharff and
Jacobs, 2006)
at ¼ 1
P 3
i¼1 cAC0;ik1;ie k1; i t
where,
at = landfill gas product ion at a given time (m 3/year)
1= dissim ilation factor
i = waste fraction with degradation rate k1 ,i
c = conversion factor (m 3 of LFG/kg of org. matter degraded)
A= am ount of waste (tonne)
C0 = amount of organ ic matter (kg of org. m at ter /tonne of waste)
k1,i = degradation rat e constan t of fraction i (year -1)
t = time elapsed since depositing (year)
In th is m ultiphase m odel, eight
w aste categories and three
fract ions are dist inguished . For
each fraction LFG production is
calcu lat ed separately.
Based on Netherlands waste
characteristics.
Organic m att er or carbon
conten t data were not available
for all waste categories.
EPER France
(Scharff and
Jacobs, 2006)
FECH4 ¼
P
xFE0 ð
P
1 ;2;3 Ai pi ki e ki t Þ
where,
FECH4 = annual methane produ ction (m3/year)
FE0 = methane generation potential (m 3/tonne of waste)
Ai = norm alisation factor
pi = w aste fraction w ith degradat ion rat e ki
ki = degradation rate of fraction i (year 1)
t = age of waste (year)
It gives tw o approaches, either
of w hich can be used for the
estimat ion of methane
generat ion from landfill. The
second approach has been
explained in this paper based on
ADEME model.
The left and righ t hand side of
the equation is not
d imensionally m atched.
However, a normalisat ion factor
is included in the m odel
equation, but it seems it is
missing from the spreadsheets.
The model m ent ions three
waste category and different k
values for each category.
(continued on next page)
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differen t countr ies has been sum marised in Tab le 8. In most of the
studies listed in Table 8 , WTE opt ion w as recom mended as a
poten tia l t echnology w ith m in im um environm ent al im pacts.
The cost analysis of differen t WTE technologies w as taken from
the previously published literatu res (Ouda et al., 2016; Yap and
Nixon , 2015; Tolis et al., 2010) and are presented in Tab le 9. The
cap ital cost is t he in it ial investm en t cost such as, land acquisit ion ,
equ ipm en t p rocurement , raw m ateria l requ irem ent ; and the
indirect costs include t he cost of p lann ing, con tractua l support,
an d techn ical & financial services throughou t the development
st age. Th e operation cost is t he daily running cost such as labour
an d m ain tenance cost . The cap ital cost for a WTE plan t depends
on t he quality of w aste to be processed , t he technology em ployed
an d its loca tion. The average lifet im e of a WTE facility has been
considered as 30 years. The range of cost as given in Table 9 is valid
for bot h developed and develop ing coun tries. The low er va lue of a
range of cost rep resents the cost in deve lop ing count ries (such as
India) and t he higher va lue represen ts the cost in developed coun-
t ries (such as UK) (Yap and Nixon, 2015). The cost s as show n in t he
Table 9 are the estim ated costs, as the actua l cost depends on var-
ious ot her factors such as, govern m en tal incen t ives, raw m ater ial
an d the availability of skilled labour (Ouda et al., 2016).
6. Environm ental and heal t h im pacts
MSW incineration m ay resu lt in air pollu t ion (due to the em is-
sions of SOx, NOx, COx, d ioxin and fu rans), soil and w ater pollution
(due to the presence of heavy m etals in the fly ash and bottom
Table 7 (continued)
Models Form ula Model descrip tion Rem arks
EPER Germ any
(Sch arff and
Jacobs, 2006)
Me ¼ M BDC BDCf F D C
wh ere,
Me = am ount of d iffuse methane emission (tonne/year)
M = annual am ount of landfilled w aste (tonne/year)
BDC = prop. of biodegradable C (tonne of C/tonne of waste), 0.15
BDCf = proportion of biodegradable C converted, 0.5
F = calcu lation factor of carbon converted into CH4, 1.33
D = collection efficiency (for, active degassing, D = 0.4, for no recovery,
D = 0.9, and for active LFG recovery and cover , D = 0.1)
C= methane concent ration , 50%
It is a zero order model that
takes unconditioned resident ial
and com mercial waste.
For the em ission estimate
purpose, coarse household
w aste, household w aste and
commercial waste w ere
considered.
The model is useful for the
estimation of large fluctuation
of m ethane emissions.
It is basically used in Germany.
Table 8
Observation s on the case studies of available WTE options.
References Study area Description of the study Critical observation
Abila (2014) Nigeria Review of opt ions for deriving energy and im proving mater ial
recovery from MSW
Due to the high percentage of biodegradable conten t in Nigeria,
biogas product ion from MSW is the best option.
Paleologos et al.
(2016)
UAE Role of recycling and in cineration for effective managem ent of
w aste of h igh incom e countries by energy and m aterial recovery.
Recycling and incineration appeared to be most feasible w aste
managem ent solu tion , because the Abu Dhabi and Dubai, the two
most urban ised and populated cities were located in the coastal
areas of UAE, w here landfilling is not advisable due to lack of
appropriate hydrogeological condition.
Korai et al.
(2016)
Hyderabad,
Pakistan
Differen t t reatment options have been evaluated using pow er
generat ion poten tial for possible w aste to energy recovery.
Maximum power generating potential w as show n by
biochemical and thermochemical m ethods respectively, but
again the single strat egy is not sufficien t to provide the solut ion .
Jesw ani and
Azapagic
(2016)
UK Identification of environm entally sustainable WTE option
amongst incineration and landfi ll gas recovery using Life Cycle
Assessm ent.
From energy recovery perspective, incin eration has lesser impact
than landfilling w ith gas recovery. In current scenario, divert ing
all the MSW intended for landfilling to incinerat ion with energy
recovery, it could meet 2.3%of UK’s electr icity dem and and
would save 2–2.6 million tonnes of GHG emissions per year.
Fruergaard and
Astrup
(2011)
Denmark Evaluat ion of energy recovery and em ission potent ial of
incineration and AD for source separat ed organ ic w aste and
m ixed high calor ific waste using LCA.
Waste incineration w ith energy recovery proved to be an
environmentally sust ainable solu tion for overall waste
managem ent, whereas AD is a least preferable based on Danish
condition.
Psom opoulos
et al. (2009)
USA Current status of WTE facilities in USAw ith regard to GHG, dioxin
and mercu ry em issions, energy production and land
conservation.
The emission of toxic and dangerous substances from WTE
facilit ies have been sign ificant ly reduced in the last decade with
the advancement of technologies. Also, the WTE facilities in USA
have quite lesser emission as com pared to other power
production facilit ies from con ventional fuel.
Cheng and Hu
(2010)
China Environmental and economic im pact of w aste incineration
technology in China.
WTE incinerat ion is expected to have a greater cont ribution in
fu ture renewable energy resources along w ith the solu tions to
waste relat ed problems of developing countries.
Noor et al.
(2013)
Malaysia Estim at ion of energy potential of landfill gas for possible
m ethan e recovery.
Methane recovery from landfill gas will not only reduce the
burden of GHG from the environm ent, but also provides a cleaner
fu el, which will act as an alternative to fossil fuels.
Curry and Pillay
(2012)
Montreal,
Canada
Feasibility analysis of AD process by estim at ion of biogas
product ion poten tial of urban food wastes using ultim ate
analysis, m olecu lar formula analysis, com puter sim ulation
techniques and a lit erature review.
The decentralised or sm all-scale AD un it is an ideal solution for
the generat ed organic waste of an urban centres, which will save
the waste transportation cost along w ith reduction in the amount
of waste sen t for landfilling.
Table 9
Cost comparison of WTE technologies.
WTE technologies Capital cost
(US$/tonne
of MSW/year)
Operational cost
(US$/ tonne of
MSW/year)
Incineration 400–700 40–70
Pyrolysis 400–700 50–80
Gasification 250–850 45–85
Anaerobic digestion 50–350 5–35
Landfilling w ith Gas recovery 10–30 1–3
12 A. Kumar, S.R. Samadder / Waste Management xxx (2017) xxx–xxx
Please cit e this article in press as: Ku m ar, A., Sam add er, S.R. A review on tech nological options of wast e to energy for e ffective managem ent of m u n icipal
solid waste. Waste Managem en t (2017), h ttp://dx.doi.org/10.1016/j.w asm an.2017.08.046
ash ). Bu t t here has been a sign ifican t developm ent in the pollu t ion
con trol techn ologies and energy recovery system s for incinerat ion,
wh ich m ade it an at t ractive MSWM option (Dam gaard et al., 2010).
The use of air pollut ion cont rol equ ipm ent in incineration plan ts is
main ly to captu re part icu late m atte rs, n itrogen oxides, dioxin and
furans for m in im isat ion of the en vironm en tal im pact s than the
convent ional coal based the rm al pow er plan ts (Liam sanguan and
Gheewala, 2007).
Num erous studies reported the perceived health risk of w aste
incinera tion plan ts. Even t he developed coun tries (such as UK)
are facing public opposit ion due to perce ived healt h risk due to
em issions from incinerat ion p lan ts (Nixon