Content uploaded by Rafiu Olasunkanmi Yusuf
Author content
All content in this area was uploaded by Rafiu Olasunkanmi Yusuf on Oct 16, 2017
Content may be subject to copyright.
Methane emission by sectors: A comprehensive review of emission
sources and mitigation methods
Rafiu O. Yusuf
a
, Zainura Z. Noor
a,
n
, Ahmad H. Abba
a
, Mohd Ariffin Abu Hassan
a
,
Mohd Fadhil Mohd Din
b
a
Environmental Engineering Laboratory, Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru, Malaysia
b
Department of Environmental Engineering, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru, Malaysia
article info
Article history:
Received 28 February 2012
Accepted 6 April 2012
Keywords:
Methane
Mitigation
Anthropogenic
Climate change
Global warming
Abatement
abstract
The global threat caused by increasing surface temperature has led to negative climate changes. One of
the greenhouse gases responsible for this global warming is methane. It is emitted naturally and
anthropogenically from different sources and its concentration in the atmosphere has assumed
alarming proportions. Its devastating consequences on climate change and atmospheric chemistry
have made it to be a focus of intense scrutiny and study. The anthropogenic sources of its emissions are
generally grouped under three sectors of agriculture, energy and waste. The past emission trends of
methane from these sectors are investigated through their sources while mitigation and abatement
strategies are suggested. It is observed that the agricultural sector emits the highest amount of
methane, followed by the energy and waste sectors, respectively.
&2012 Elsevier Ltd. All rights reserved.
Contents
1. Introduction .....................................................................................................5060
2. Agriculture ......................................................................................................5060
2.1. Source description ..........................................................................................5061
2.2. Mitigation measures for the agricultural sector . . .................................................................5062
2.2.1. Dietary supplementation ..............................................................................5062
2.2.2. Selection of high quality grasses . . . .....................................................................5062
2.2.3. Increase grain level ..................................................................................5062
2.2.4. Increasing feed conversion efficiency ....................................................................5062
2.2.5. Increasing animal productivity .........................................................................5062
2.2.6. Future options ......................................................................................5063
2.2.7. Methane emissions mitigation from manure management ...................................................5063
2.2.8. Biogas production....................................................................................5063
2.3. Mitigation for rice cultivation .................................................................................5063
3. Energy . . .......................................................................................................5063
3.1. Source description ..........................................................................................5064
3.1.1. Oil and gas . . .......................................................................................5064
3.1.2. Coal mining activities. . . ..............................................................................5064
3.1.3. Stationary and mobile sources..........................................................................5064
3.1.4. Biomass burning.....................................................................................5064
3.2. Mitigation options for the energy sector.........................................................................5064
3.2.1. Oil ................................................................................................5064
3.2.2. Natural gas . . .......................................................................................5065
3.2.3. Coal...............................................................................................5065
4. Waste . . . .......................................................................................................5066
Contents lists available at SciVerse ScienceDirect
journal homepage: www.elsevier.com/locate/rser
Renewable and Sustainable Energy Reviews
1364-0321/$ - see front matter &2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.rser.2012.04.008
n
Corresponding author. Tel.: þ60 177 470 315.
E-mail address: zainurazn@utm.my (Z.Z. Noor).
Renewable and Sustainable Energy Reviews 16 (2012) 5059–5070
4.1. Source description ..........................................................................................5066
4.1.1. Solid waste landfill...................................................................................5066
4.1.2. Wastewater ........................................................................................5066
4.1.3. Source Results ......................................................................................5067
4.2. Abatement options for lan dfills and wastewater plants .............................................................5067
4.2.1. Emissions reductions from landfills......................................................................5067
4.2.2. Wastewater methane emission abatement . . . .............................................................5067
5. Conclusions .....................................................................................................5067
References ......................................................................................................5067
1. Introduction
The emission of greenhouse gases from various sources has
resulted in climate change with the attendant increase in global
surface temperature [1,2]. Climate change, a resultant effect of
greenhouse gas emissions, is a worldwide concern because its
continuation is having significant and negative impacts on people,
natural resources, and economic conditions around the globe
[3–7]. The major greenhouse gases (GHGs) and their relative
quantities are water vapour, H
2
O
(g)
(36–70%), carbon dioxide,
CO
2
(9–26%), methane, CH
4
(4–9%), and nitrous oxide N
2
O (3–7%)
plus other trace gases [8]. Of these greenhouse gases, CO
2
and CH
4
have been touted as being responsible for the rise in global
surface temperature [9]. The emissions of these gases are caused
by both natural and human (anthropogenic) actions.
Methane is only second to carbon dioxide in its contribution to
global warming [10]. It is the simplest alkane and is also the
principal component of natural gas with bond angles of 109.51
and is formed from the anaerobic decomposition of organic
matter in the environment. Methane is a much more powerful
greenhouse gas than CO
2
with a high global warming potential
(GWP) of 21–25 times more than CO
2
[11–15]. The 100-year
GWPs of the greenhouse gases as given in the Second (SAR), Third
(TAR) and Fourth (AR4) Assessment Reports are shown in Table 1
[16,17]. Methane is said to be explosive when it is present in the
air in concentrations between 5–15% [18,19]. The yearly CH
4
emissions around the world are significantly smaller than CO
2
emissions, and CH
4
concentrations in the atmosphere are about
200 times lower than those of CO
2
[20], but methane accounts for
about 20% of global warming [21,22].
It is emitted naturally by wetlands [23,24], termites, wildfires
[20], grassland [25], coal beds [26,27] and lakes [28]. The human
(anthropogenic) sources of methane emissions include municipal
solid wastes (MSW) landfills [29–31], rice paddies [32–34], coal
mining [35–37], oil and gas drilling and processing [38,39], cattle
ranching [40–42], manure management [43,44], agricultural pro-
ducts [45,46], wastewater treatment plants [47], and rising main
sewers [48].
Methane concentration in the atmosphere remained stable for
thousands of years before it began to rise in the 19
th
century
(Fig. 1a). In 1750, the concentration of methane in the atmosphere
was 676–716 ppb. It rose to 1745 ppb in 1998 and 1800 ppb in
2008 [15,17,49]. The global anthropogenic emissions for methane
from all sectors in 2010 were estimated to be 6,875 million metric
tons CO
2
equivalent (MtCO
2
eq) [50,51].
This review examines the emissions of methane from 1990 to
2010 and provides explanation as to the trends observed. Anthro-
pogenic methane emissions pattern from all sources for 2010 are
presented in Fig. 1b. The major sources of methane emissions that
have been identified are grouped into three main sectors –
agriculture, waste, and energy. The sectorial emissions for 2010
are also presented in Fig. 1c while Fig. 1d shows the methane
emissions trends from 1990 to 2010. The overall emission pattern
indicated growths of 4%, 9%, 15% and 23.5%, respectively, for the
years 1995, 2000, 2005 and 2010 over the 1990 emission level.
These emissions are projected to grow by a further 32% and 41%
respectively by the years 2015 and 2020 [51]. Methane emissions
from the agricultural sector increased by 11% by the year 2000
and 24% by the end of 2010. The emissions from the energy sector
also increased by 8% in 2000 and 32% by 2010 while the waste
sector recorded increases of 4% and 12% by the end of the years
2000 and 2010 respectively. The raw data used in this review
were obtained from the report by the US Environmental Protec-
tion Agency (EPA).
The patterns of methane emissions from these sectors as well
as strategies for the mitigation of these methane emissions from
each sector are exhaustively discussed in the following sections.
2. Agriculture
The average global emissions of methane from the agricultural
sector through human (anthropogenic) activities were 3,520
MtCO
2
eq which is 52.5% of the total methane emissions from
anthropogenic sources [51]. Of these agricultural emissions, those
from enteric fermentation (livestock rearing) alone was 53% [6]
while emissions from rice cultivation, other agricultural activities
and manure management were 18%, 18% and 11%, respectively
(Fig. 2a) [51]. Globally, methane emissions from ruminant live-
stock is 85 Tg of the 550 Tg released annually [52].
Methane emissions from enteric fermentation rose by only
1.5% between 1990 and 2000 but the increase rose to 17% by the
end of 2010 [53]. Rice cultivation resulted in a 6% increase in
methane emissions from 1990 to 2000 and this shot up to 18% by
2010. Methane emissions from manure management increased by
only 1% from 1990 to 2000 but the increase rose to 12% by the
year 2010 [53]. Emissions increase from other agricultural sources
has remained constant. The trends of methane emissions in the
agricultural sector from 1990 to 2010 are illustrated in Fig. 2b.
Table 1
Composition of 100-year GWP of the greenhouse gases.
Gas SAR TAR AR4
CO
2
111
CH
4
21 23 25
N
2
O 310 296 298
HFC-23 11,700 12,000 14,800
HFC-32 650 550 675
HFC-125 2,800 3,400 3,500
HFC-134a 1,300 1,300 1,400
HFC-143a 3,800 4,300 4,470
HFC-152a 140 120 124
HFC-227ea 2,900 3,500 3,200
HFC-236fa 6,300 9,400 9,810
HFC-4310mee 1,300 1,500 1,640
CF
4
6,500 5,700 7,390
C
2
F
6
9,200 11,900 12,200
C
4
F
10
7,000 8,600 8,860
C
6
F
14
7,400 9,000 9,300
SF
6
23,900 22,200 22,800
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059 –50705060
The main reason for this upward increase in methane emis-
sions is the rising levels of agricultural production with the aim of
meeting the demands of rapidly-growing population centres in
China, South and East Asia, Latin America, and Africa. Consump-
tion of agricultural products is rising quickly due to increases in
both population and income in many areas of these regions.
Another factor that will cause increase in the demand for
agricultural products is changes in diet preferences, such as an
increase in per-capita meat consumption [51]. Overall, global
anthropogenic methane emissions from livestock alone is esti-
mated at 35–40% [54], 37% [55] and 25.5% [56].
2.1. Source description
The normal processes of digestion in animals result in methane
emissions. Enteric fermentation is a fermentation process in which
microbes in the animal’s digestive system cause the food to be
fermented [40,56,57]. This fermentation takes place in the rumen
of ruminant animals like cattle, buffalos, sheep, and goats and
result in relatively large methane emissions per unit of feed energy
consumed [56]. Methane emissions from enteric fermentation of
the domestic livestock contribute significantly to GHG inventories
[42,58,59]. Majority of methane emissions in this sector are from
domesticated ruminants such as cattle, buffalo, sheep, goats, and
camels. Methane emissions by other domesticated non-ruminants
such as swine and horses are relatively small [60]. Total emissions
are driven by the size of livestock populations and the type of
management practices, especially the feed regime used. Also
affecting methane emissions are the quantity, quality, and type
of feed [51]. The top five countries with respect to global methane
emissions from enteric fermentation are China, Brazil, India, the
U.S., and Russia [51].Table 2 shows the world and regional distri-
bution of domesticated ruminant population.
Aerobic decomposition of organic material during flooding of
the rice field gradually reduces the oxygen present in the soil and
water. This causes the development of anaerobic conditions in the
soil and methane is produced through anaerobic decomposition
53%
11%
18%
18% Enteric fermentaion
Manure managemen
t
Rice cultivation
Other agric activities
0
500
1000
1500
2000
2500
3000
3500
4000
1990 1995 2000 2005 2010
Emissions (MtCO2eq)
Year
Enteric fermentation Rice cultivation
Manure mana
g
ement Other a
g
ricultural activities
Fig. 2. (a) Methane emissions from agriculture. (b) Methane emissions trend from
the agricultural sector (1990–2010).
0
200
400
600
800
1000
1200
1400
1600
1800
1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100
ppb of CH4
Year
Antartica Greenland Tasmania
Fig. 1. (a) Methane concentration in the atmosphere. (b) Anthropogenic methane emissions by source in 2010. (c) Anthropogenic methane emission by sectors in 2010.
(d) Methane emission trends by sectors from 1990–2010.
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059–5070 5061
of soil organic matter by methanogenic bacteria [62,63]. The
amount of methane produced depends on water management
practices and the quantity of organic material available for
decomposition [64]. China and South and East Asian regions are
the largest sources of methane emissions from rice cultivation.
The single largest contributors in these regions are China, India,
Thailand, Indonesia, Vietnam, and Myanmar, which together emit
78% of all emissions from rice cultivation [51]. It is anticipated
that yield growth, as opposed to acreage growth, will continue to
be the main source of the production growth, with the continued
development and adoption of higher-yielding rice varieties in
many producing countries [65]. Thailand, Vietnam, and India are
projected to dominate global rice exports through the 2005 to
2015 projection period, with an estimated 60% or greater share of
the global export market [51]. China is expected to continue to be
a significant contributor, but at a lower rate of growth due to
decreases in production area [65].
Anaerobic decomposition of manure leads to the production of
methane [51]. Three primary factors affect the quantity of
methane emitted from manure management operations. These
are the type of treatment or storage facility, the ambient climate,
and the composition of the manure [43,66]. Storage and treat-
ment of manure in liquid systems such as lagoons, ponds or pits
leads to the development of anaerobic conditions which result in
methane emissions. Higher ambient temperature and moisture
content favour methane production. The composition of manure
is directly related to animal types and diets [67]. For example,
milk production in dairy cattle is associated with higher feed
intake, and therefore higher manure excretion rates than non-
dairy cattle. Also, supplemental feeds with higher energy content
generally result in a higher potential for methane generation per
unit of waste excreted than lower quality pasture diets. In some
instances, some higher energy feeds are more digestible than
lower quality forages, which can result in less overall waste
excreted. Consequently, a combination of all these factors will
affect the actual emissions from manure management systems
[51]. Methane emissions from manure management are largely
from the OECD (Fig. 2d). The top emitting countries are the U.S.,
Germany, India, China, France, Russia, Turkey, and Brazil [51].
Methane is produced from the open burning of biomass during
agricultural activities and from land use change [68,69]. The
sources included in this section are savannah burning, agricul-
tural residue burning, and open burning from forest clearing.
This category also includes minor amounts of country reported
emissions data on methane from agricultural soils [70]. However,
biomass burning constitutes the majority of emissions for this
source category. Latin America, Africa, and South and East Asia are
the largest emitters in this source category. These three regions
account for 85% of the methane emissions [51].
2.2. Mitigation measures for the agricultural sector
The mitigation of methane emissions from the agricultural
sector is briefly described.
2.2.1. Dietary supplementation
The use of long-chain fatty acids in the diet of the ruminants in
the form of processed oilseeds (like canola seed) will reduce
methane emissions without affecting diet digestibility [57,71–73].
The use of lipids with ionosphores (such as monensin) in the diet
will also cause a reduction in methane emissions [74]. Monensin
causes a change in the bacterial species in the rumen resulting in
an increased proportion of propionate or could cause a decrease in
the numbers of rumen protozoa in the rumen [73]. Linseed fatty
acids reduce methane emission but have a negative effect on milk
production [75]. Sunflower oil in the diet will reduce methane
emission [76]. Incorporating fat in the diet as an energy source
lowers the carbohydrate content, which is the substrate for CH
4
formation while the numbers of protozoa in the rumen are also
lowered by the fats with many of them physically associated with
the methanogens [73]. A reduction in methane emission was
noticed when low protein diet was supplemented with amino
acids [77].
Effects of short term oral nitroethane administration on
methane emissions have been investigated and found to reduce
emissions and is an effective anti-methanogenic compound in
ruminants fed high forage diets [41]. Combining feed additives
like fermented mixed rations of whole–crop rice and rice bran
[78] and a mixture of lauric acid, myristic acid, linseed oil and
calcium fumarate [79] were found to lower methane emissions.
On the other hand a combination of diallyl disulphide, yucca
powder, calcium fumarate and linseed oil and another combina-
tion of capric acid and caprylic acid were found to have no
marked effect on methane emission reduction [80].
2.2.2. Selection of high quality grasses
High quality grasses with high concentration of water-soluble
carbohydrates, forage legumes containing secondary metabolites
(tannings) and fruits/plants containing saponins have been found
to reduce methane emissions [57,81–84].
2.2.3. Increase grain level
Feeding grains and whole plant silages to the animals will
reduce methane emission [85,86]. Increasing the level of grain in
the diet reduces methane emission because the percentage of the
energy consumed that is converted to methane in the rumen is
typically reduced to about 3%, from the 6.5% or more that is
common for animals fed primarily forages [76]. However, the
grain must comprise more than 90% of the diet for any reduction
in methane emission to occur [87].
2.2.4. Increasing feed conversion efficiency
Enteric methane emissions could be reduced by improving the
efficiency of converting feed to meat and milk [88]. Less enteric
methane is generated when the amount of feed it takes to
produce animal products is reduced because methane emissions
are related to feed intake. This increased efficiency of production
can be achieved through animal breeding and improved nutrition
[57,81,87].
2.2.5. Increasing animal productivity
Increasing the productivity of individual animals so that fewer
animals are required to produce the same amount of product will
cause a reduction in methane emission. While the total amount of
methane produced per kilogram of milk or meat declines, methane
emissions per animal increase [88]. Overall, however, a reduction in
methane occurs because animal numbers decrease [89].Improved
feeding and animal genetics in the beef industry can reduce the time
cattle are on feed and this will impact on lifetime methane
emissions. Furthermore, improving reproductive performance of
Table 2
World and regional distribution of domesticated ruminants (10
6
).
Source:[61]
Animal
type
World Africa North
America
South
America
Asia Europe Oceania
Cattle 1347 270 111 315 431 127 38
Buffalo 181 5 – 1 174 0.33 0.0002
Sheep 1078 288 7 73 452 134 113
Goat 862 291 3 21 516 18 1
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059 –50705062
cattle can reduce total methane emissions from the herd by
reducing the number of replacement heifers required [57,87,90].
2.2.6. Future options
Genetic selection of animals, vaccination, probiotics, prebiotics
and plant improvement have also been suggested as the most
promising future options for methane emissions mitigation [91].
A variety of emission reduction options that can be applied at
reasonable costs includes [92] (a) carbon sequestration on exten-
sively used grazing land, (b) reduction of methane emissions from
low-input ruminant production and (c) reduction of methane
emissions from animal waste through the recovery of energy and
waste management improvement.
2.2.7. Methane emissions mitigation from manure management
Methane emissions mitigation from manure management
dwells much more on slurry systems. There is a direct correlation
between methane emission and manure piling height. Lower
stacking or piling of the manure leads to lower methane emission
[43,93]. Dilution of animal manure before treatment reduces
methane emission (Su et al., 2003. Daily flushing and cooling of
the slurry will cause a substantial reduction in methane emission
[94]. Anaerobic digestion of the manure before outside treatment
will cause a reduction in methane emission [67,95]. A reduction
in methane emission from the manure of animals fed with low-
protein diet that is supplemented with synthetic amino acids has
been observed [77]. When compared to broadcasting, application
of manure by trail hose and injection reduces methane emission
by 0.7 and 3.2% respectively [96].
2.2.8. Biogas production
Studies have shown that production of biogas from manure, a
renewable form of energy, will reduce methane emissions
[3,97–103]. This biogas could be channelled to industries and
improve overall eco-efficiency through the creation of industrial
symbiosis [104–109]. With an annual biomass production of 220
billion tonnes [110] and studies carried out on household biogas
use [111], the importance of this form of energy with respect to
strategic and policy shift from fossil fuels cannot be overempha-
sised [112].
2.3. Mitigation for rice cultivation
Methane emission mitigation from rice production can be
achieved by the appropriate selection of rice cultivar, water
regime and fertilizers and has been shown that rice breeds with
heavier total weight emit less methane [113,114]. The incorpora-
tion of rice straw compost before transplanting and fresh rice
straw three months before transplanting, coupled with intermit-
tent irrigation, brought methane emissions down by 49% and 23%
respectively [115]. Drainage of the field during the flowering
period and the application of potassium lowered the emission of
methane [116,117].
3. Energy
The energy sector is second to agriculture in contribution to
global emissions of methane. Methane emissions trend from this
sector between 1990 and 2010 is shown in Fig. 3a. Emissions from
the oil and gas sector have been on the increase and this trend
will continue in view of the expanding economies of the ‘BRIC’
countries (Brazil, Russia, India, and China). The largest source of
methane emissions in the energy sector are fugitive emissions
from natural gas and oil systems [51]. They constitute approxi-
mately 17% of total man-made sources of global methane emis-
sions and in 2005 totalled approximately 82 billion m
3
(Bcm),
(1165 MtCO
2
eq) [118]. About 28 Bcm (420 MtCO
2
eq) of methane
are released to the atmosphere annually from coal mining
activities around the world [119]. Approximately 88% of all
Fig. 3. (a) Methane emissions trends from the energy sector. (b) Global methane emissions from oil and natural gas operations. (c) Top five methane emitting countries
from oil and gas.
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059–5070 5063
methane emissions from coal mining originate from only ten
countries with the top five, in order of emissions, being China,
United States, India, Ukraine and Australia [37]. China is the
biggest coal producer in the world with an annual coal output of
2.79 billion tonnes in 2008 [120]. Chinese coal mines emitted up
to 18 billion m
3
(270 MtCO
2
eq) of methane into the atmosphere
in 2007 [121]. Decrease in methane emissions from coal mining is
envisaged because of a change in sources of energy from coal to
natural gas in several areas in Eastern Europe and the Former
Soviet Union (FSU) [51].
3.1. Source description
3.1.1. Oil and gas
Methane makes up about 95% of natural gas and is emitted
from natural gas production, processing, transmission and dis-
tribution. Significant quantities of methane are also emitted from
oil production and processing as natural gas is often found in
conjunction with petroleum deposits. Methane is a fugitive
emission in both oil and natural gas systems, from leaking
equipment, system upsets, and deliberate flaring and venting at
production fields, processing facilities, transmission lines, storage
facilities, and gas distribution lines. Global oil and gas methane
emissions increased by 3.6% in 2000 from the 1990 level and by
36% by 2010 (Fig. 3a). The three key factors that have affected the
overall trend in global emissions from 1990 to 2010 are the non-
EU FSU economic transition, the mild growth in production in
parts of the OECD, and the accelerated growth in energy produc-
tion and demand in all other regions, especially Asia [51].
Fig. 3b shows global oil and gas methane emissions from oil
and gas processing for the top twenty emitting countries [118]
with the leading emitters of being Russia, US, Ukraine, Mexico and
Iran (Fig. 3c). In 1990, the non-EU FSU and OECD countries
accounted for 75% of the global methane emissions. The percen-
tage of Russia’s contribution to the global emissions will fall from
33% in 1990 to 22% by 2020 [51]. The OECD countries experienced
only mild growth of 40% compared to the developing regions
because many of these countries have mature natural gas and
oil industries, hence oil and gas activities have stagnated.
This is in addition to the institution of air quality and safety rules
by many OECD countries that have the additional benefit of
reducing methane emissions. However, it is likely there will be
a continued and growing demand for natural gas in the OECD,
which may result in increased emissions in the distribution and
transmission sectors.
The Middle East, Latin American, and South and East Asian
regions are expected to increase global methane emissions from
22% in 1990 to 33% in 2010 [51]. Electricity production and
demand are expected to increase rapidly in the less developed
countries of these regions because of populations becoming more
urbanized and concentrated with industrial expansion. The
resulting increase in energy demands are will drive the rapid
growth in fuel production and consumption. Some of the largest
oil producing and exporting countries are located in the Middle
East and emissions are expected to increase there as a result of
increasing world demand for oil.
3.1.2. Coal mining activities
Methane is produced from coal during the process of coalifica-
tion, where vegetation is converted by geological and biological
forces into coal [122,123]. It is then stored within the coal seams
and the surrounding rock strata and is liberated when the
pressure above or surrounding the coal bed is reduced as a result
of natural erosions, faulting, or mining [27,36]. The quantity of gas
emitted from mining operations is a function of two primary
factors: coal rank and coal depth [51]. Four main sources are
responsible for methane emissions from the coal mining. These
are underground mines which account for the majority of global
methane emissions from coal mining, surface mines which gen-
erally emit considerably less methane than underground mines
because coal ranks are typically lower and there is less pressure to
trap methane in the coal, post-mining operations which refer to
the processing, storage, and transportation of the mined coal and
abandoned mines where methane emissions from coal mines
continue after operations have ceased [50].
There was significant decline in global coal mine methane
emissions 1990 to 2000, but increased steadily after 2000
(Fig. 3a). The changes in coal production in China, restructuring
of the energy industries in Europe and the non-EU FSU, and
industry changes in the U.S are the factors that will affect the
expected trend. China’s emissions are expected to increase 50% by
2020 due to increased coal production to meet expanding energy
needs [120]. Reduced coal production in England and Germany in
the 1990s contributed substantially to the reduction in OECD
emissions from 1990 to 2000. In Russia and Eastern European coal
producing countries, restructuring of the energy industries caused
many of the gassiest underground mines to close during the
1990s resulting in a decrease in emissions that has been sustained
in the projection years. In the US, decreased emissions from coal
mining activities are expected through 2020 because of shift in
production from underground to surface coal mines. Reductions
due to methane recovery and use of coal bed methane will cause a
reduction in methane emissions.
3.1.3. Stationary and mobile sources
Methane is emitted from stationary and mobile combustion as
a result of incomplete combustion. However, combustion is a
relatively minor contributor to overall methane emission.
Methane emissions increased from 199 MtCO
2
eq in 1990 to 218
and 235 MtCO
2
eq in 2000 and 2010 respectively (Fig. 3a) [51].
3.1.4. Biomass burning
Incomplete biomass combustion leads to the production of
methane. The major contributors to methane emissions within
this category are municipal waste combustion, charcoal, fuel
wood, agricultural residues, and agricultural waste. In the devel-
oping world biomass combustion often refers to the combustion
of biofuels in small-scale combustion devices for heating, cooking,
and lighting purposes. Estimates for this category are highly
uncertain and difficult to predict because of the wide variety in
the types and conditions under which these fuels are burned.
Methane emissions increased from 184 MtCO
2
e in 1990 to 206
and 226 MtCO
2
e in 2000 and 2010, respectively (Fig. 3a) [51].
3.2. Mitigation options for the energy sector
Methane is emitted in the oil and gas sector during normal
operations, system disruptions and routine maintenance. These
emissions can be cost-effectively reduced through the upgrade of
technologies or equipment and by operational improvement.
Some mitigation and abatement options for each unit are briefly
discussed. Mitigation options for coal methane are grouped
into four.
3.2.1. Oil
The mitigation and abatement options applicable to the oil sector
are vapour recovery units, flaring, direct use, and reinjection of gas
into oil fields for enhanced oil recovery [51,60,124,125].
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059 –50705064
3.2.1.1. Install vapour recovery units. Light hydrocarbons vaporise
out of solution during the storage of crude oil. These hydrocarbons
are then vented into the atmosphere. The vapour recovery unit will
capture these vapours for use as fuels or for sale.
3.2.1.2. Flaring in place of venting for both offshore and onshore
gas wells. When flaring system is installed, an estimated 98%
reduction in fugitive emissions occurs through the burning of
vented gas where methane is converted to carbon dioxide. It is
more expensive to install a flare in an offshore environment due
to technical, environmental, and safety concerns.
3.2.1.3. Direct use of methane. Another abatement option applies
primarily to offshore platforms with an estimated reduction
efficiency of 90%. This abatement option allows methane to be
used for consumption on oil platforms and/or converted to
liquefied natural gas.
3.2.1.4. Reinjection of methane. An alternative to flaring or direct
use is reinjection of methane where the captured gas from
oil field operations is re-injected into the oil production field so
as to enhance future oil recovery. This method is estimated to
have a reduction efficiency of 95% with a technical lifetime of
15 years.
3.2.1.5. Plunger lift system. A plunger lift can be used to effectively
push the fluids out of the well instead of ‘venting’ gas wells to the
atmosphere.
3.2.2. Natural gas
The mitigation and abatement options for each segment of the
natural gas system are in the production, processing, transmission
and distribution stages [51,124,125].
3.2.2.1. Production abatement options. The production segment of
the natural gas sector consists of wells, compressors, dehydrators,
pneumatic devices, chemical injection pumps, heaters, meters,
pipeline, and central gathering facilities. Available abatement
technologies associated with this segment include
a. use catalytic converters in selected well field engines and
compressors,
b. replace wet seals with dry seals in centrifugal compressors,
c. direct/enhanced inspection and maintenance at production
sites,
d. installation of flash tank separator in glycol dehydration
systems,
e. replace high-bleed pneumatic devices with low bleed devices
or with instrument air (compressed, dry air) systems, and
f. optimise glycol recirculation rates.
3.2.2.2. Processing abatement options. The processing segment
consists of gas plant facilities that encompasses the use of
vessels, dehydrators, compressors, acid gas removal (AGR) units,
heaters, and pneumatic devices. The technologies for abatement
associated with the segment are
a. retrofit fuel gas for reciprocating compressors and blowdown
valve,
b. replace wet seals with dry seals in centrifugal compressors,
c. convert gas pneumatic controls to instrument air (compressed,
dry air), and
d. Direct inspection and maintenance (DI&M) at gas processing
plants.
3.2.2.3. Transmission abatement options. The transmission segment
of a natural gas system comprises the transmission pipeline
networks, compressor stations, and meter and pressure-regulating
stations. The available abatement technologies include:
a. convert gas pneumatic controls to instrument air (compressed,
dry air),
b. use pipeline pumpdown techniques to lower gas line pressure
before maintenance,
c. DI&M at compressor stations and surface facilities for leak
detection,
d. replace wet seals with dry seals in centrifugal compressors,
and
e. replace compressor rod packing systems.
3.2.2.4. Distribution abatement options. The distribution segment
is made up of the main and service pipeline networks, meter and
pressure regulating stations, pneumatic devices, and customer
meters. The abatement technologies in this segment include
a. use hot taps in service pipeline connections,
b. DI&M at gate stations,
c. use composite wrap for non-leaking pipeline defects, and
d. use a pipeline pumpdown technique to lower gas line pressure
before maintenance.
3.2.3. Coal
When fugitive methane gas from underground coal mines is
removed and used in profitable and practical ways, worker safety
will be improved, mine productivity will be enhanced, revenues
will increase, and greenhouse gas emissions will be reduced [50].
Four abatement options are currently available in the coal mining
sector. These are degasification and pipeline injection, enhanced
degasification, oxidation of ventilation air methane and flow
reversal.
3.2.3.1. Degasification and pipeline injection. High-quality methane
is recovered from coal seams when one of the following
degasification methods is employed [50,119]: (1) vertical wells
(drilled from the surface into the coal seam months or years in
advance of mining), (2) gob wells (drilled from the surface into
the coal seam just prior to mining), and (3) in-mine boreholes
(drilled from inside the mine into the coal seam or the
surrounding strata prior to mining). The quality (purity) of the
gas that is recovered depends partially on the degasification
method employed, and determines how the gas can be used. For
example, only high quality gas (typically greater than 95%
methane) can be used for injection into natural gas pipelines.
Vertical wells and horizontal boreholes into the coal seam tend to
recover nearly pure methane (greater than 95% methane). High
quality methane can be recovered from very gassy mines, when
gob wells are drilled into the gob zone of mined-out coal seams,
especially during the first few months of production. This method
will cause a 28% emission reduction.
3.2.3.2. Enhanced degasification. In enhanced degasification,
methane is recovered in the same way as in degasification,
using vertical wells, horizontal boreholes, and gob wells.
Furthermore, enrichment technologies such as nitrogen removal
units (NRUs) and dehydrators are used primarily to enhance
medium-quality gob well gas by removing impurities, thereby
allowing larger quantities of methane to be captured and used.
It is assumed in this option that well spacing will be tighter for
recovery to increase. This process improves recovery efficiency
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059–5070 5065
20% more than the degasification option [126]and causes a 10%
emission reduction.
3.2.3.3. Oxidation of ventilation air methane (VAM). Methane
emitted from coal mine ventilation air can potentially be
utilised by oxidation technologies (both thermal and catalytic).
Extremely low methane concentration levels (typically below 1%)
render the sale of this gas to a pipeline not economically feasible.
However, CO
2
and heat could be generated from an oxidised
VAM which in turn may be used directly to heat water or to
generate electricity. Application of oxidiser technology to all mine
ventilation air with concentrations greater than 0.15% methane
will result in the mitigation of about 97% of the methane from the
ventilation air. This method will cause a 24% emission reduction.
Medium-to-low quality methane, with concentrations ranging
from 35 to 85% can also be used as an energy source in various
applications. Potential applications that have been demonstrated
in the U.S. and other countries for lower quality coal mine
methane (CMM) include [50].
a. Electricity generation with reciprocating engines, gas turbines
or steam turbines (the electricity can be used either on-site or
can be sold to utilities);
b. As a boiler or dryer fuel in on-site preparation plants or mine
vehicle fuel,
c. As a medium-BTU fuel for nearby industrial or institutional
facilities; and
d. Cutting-edge applications, such as in fuel cells and chemical
processes.
3.2.3.4. Flow reversal. This involves the regenerative heat exchange
between a gas and a solid bed of heat exchange medium and
can utilise up to 100% of the methane from ventilation shafts. The
methane goes into and through the reactor in one direction while
temperature is increased until the oxidation of methane is
achieved. The hot products of oxidation then give up heat in
their movement towards the far side of the bed, and
the flow is reversed automatically. The application of heat
exchange technologies allows excess heat to be transferred for
local heating use, or for power production in gas or steam turbines.
It has been proved that the process is capable of sustaining
operation with ventilation air at low methane concentrations of
0.1% [126,127].
4. Waste
The waste sector is the third largest contributor to global
emissions of non-CO
2
GHGs with the two largest sources being
landfilling of solid waste and wastewater treatment. While the
sector as a whole accounts for only 15% of all non-CO
2
GHG
emissions, landfilling is the fourth largest individual source of
emissions (761 MtCO
2
eq), after agricultural soils (2,001 MtCO
2
eq),
enteric fermentation (1,772 MtCO
2
eq), and natural gas and oil
systems (993 MtCO
2
eq) [51]. Methane emissions from landfills
dropped from 761 MtCO
2
eq in 1990 to 730 MtCO
2
eq (4.1%) in
2000 and rose to 761 MtCO
2
eq in 2010 (Fig. 4a). It is projected to
reach 788 and 817 MtCO
2
eq by 2015 and 2020 respectively [51].
Emissions from wastewater, on the other hand, rose from 446
MtCO
2
eq in 1990 to 523 MtCO
2
eq in 2000 (17.3%) and 594
MtCO
2
eq in 2010, an increase of 33.2% (Fig. 4a). Methane emissions
from waste water are projected to be 630 and 665 MtCO
2
eq by
2015 and 2020 respectively [51].
4.1. Source description
4.1.1. Solid waste landfill
Methane is produced and emitted from the anaerobic decom-
position of organic material in landfills [128–130]. The major
drivers of emissions are the amount of organic material deposited
in landfills, the extent of anaerobic decomposition, and the level
of landfill methane collection and combustion (e.g., energy use or
flaring)[131].
The OECD countries emitted nearly 49% of the global methane
from the landfilling of solid wastes in 1990. Other regions con-
tributed less than 15% of the methane emissions each for this source
category. The 170 MtCO
2
eq of methane emissions from U.S. were
46% and 23% of the OECD and global total, respectively [53].
Significant shifts in landfills contributions to methane emissions
are projected because countries with more steady-state economic
growth, and small or declining population growth rates, are
expected to experience minimalgrowthinlandfillemissions[132].
The observed decline in emissions from 1990 to 1995 in the
OECD are attributed to the collection, flaring and use of landfill
methane as well as the non-climate regulatory programs that result
in mitigation of air emissions, collection of gas, or closure of facilities
[51]. In other regions where diversion of solid waste to managed
landfills as a means of improving overall waste management is
expected, an increase in methane emissions is envisaged. This will
be in addition to the combined effects of rapid economic change,
expansive growth policies, and population increase, particularly in
the urban centres of developing countries, changing consumption
patterns and increases in waste generation [132]. Areas with
projected high growth in emissions are Africa at 77% growth, S&E
Asia at 34% and Latin America at 52% growth [51].
4.1.2. Wastewater
Methane is emitted during the handling and treatment of
municipal and industrial wastewater [133]. Methane emissions
from wastewater increased by 17.3% and 33.2% in 2000 and 2010
respectively from the 1990 level of 446 MtCO
2
eq (Fig. 4a) [51].
The organic material in the wastewater produces methane when
it decomposes anaerobically. Most developed countries with
centralised aerobic wastewater treatment to handle their muni-
cipal wastewater, have low methane emissions are small and
incidental. However, in the developing countries, anaerobic sys-
tems such as latrines, open sewers, or lagoons with little or no
collection and treatment of wastewater are more prevalent.
Industrial wastewater can also be treated anaerobically, with
significant methane being emitted from those industries with
high organic loadings in their wastewater stream, such as food
processing and pulp and paper facilities [134].
0
200
400
600
800
1000
1200
1400
1600
1990 1995 2000 2005 2010
Methane emissions (MtCO2eq)
Year
Landfilling Wastewater
Fig. 4. (a) Total emissions from the waste sector (1990–2010).
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059 –50705066
4.1.3. Source Results
South and East Asia and China accounted for 33% and 24%,
respectively, of global methane emissions from wastewater hand-
ling in 1990 while Africa, OECD, and Latin America accounted for
between 10–12% each [51]. The largest emitters in 1990 were
China (21%), India (18%), U.S. (6%), and Indonesia (4%). Waste-
water methane emissions in Africa and the Middle East is
expected to increase because of population growth, particularly
growth associated with countries that rely on less advanced,
anaerobic treatment and collection systems such as latrines,
septic tanks, open sewers, and lagoons [134]. Most developed
countries have an extensive infrastructure to collect and treat
urban wastewater, in which the majority of systems rely on
aerobic treatment with minimal methane production and thus
less effect on the emissions trend [134].
4.2. Abatement options for landfills and wastewater plants
Mitigation and abatement options that are available for land-
fills and wastewater plants are discussed in the sections.
4.2.1. Emissions reductions from landfills
Vertical wells and horizontal trenches are the methods used as
collection systems in most landfills to prevent migration of gas to
onsite structures or away from the landfill to adjacent property and
to prevent the release of non-methane organic compounds to the
atmosphere. Landfill gas (LFG) can be used to produce electricity
with engines, turbines, or other technologies, and can be refined and
injected into a natural gas pipeline. Using LFG in these ways can
yield substantial energy, economic, environmental, air quality, and
public health benefits [3,97,99,100,102,110,135–141].
4.2.1.1. Collection and flaring. The presence of methane, if allowed
to build up, becomes a public health concern and a safety hazard
at landfills. Hence, methane has been removed from large landfills
and is combusted through flaring. Gas is collected through
vertical wells and a series of horizontal collectors typically
installed following the closing of a landfill cell. Vertical wells
are the most common type of well, while horizontal collectors are
used primarily for deeper landfills and landfill cells that are
actively being filled. Once captured, the gas is then channelled
through a series of gathering lines to a main collection header.
The USEPA recommends that the collection system be designed so
that an operator can monitor and adjust the gas flow.
4.2.1.2. Electricity generation. Landfill gas that is extracted using a
series of vertical or horizontal wells and a blower (or vacuum)
system is collected in a central point, where it can be processed
and treated depending on the ultimate use of the gas. From here,
the gas can be flared, used to generate electricity, or be pumped to
an enduser for process heat.
4.2.1.3. Direct utilisation of gas. Landfill gas can be directly used as
fuel to run leachate evaporators and liquid natural gas production.
In addition, landfill methane gas can be transported and used in
industrial processes, such as boilers, drying operations, kiln
operations, and cement and asphalt production. Gas collected from
the landfill can be piped directly to local industries where it is used
as a replacement or supplementary fuel.
4.2.1.4. Change in waste management practice. Waste management
practices can be changed to reduce waste disposal (waste
minimisation) at landfills by adding composting and recycling-
and-reuse (waste diversion) programs. Incineration is another
possible consideration.
4.2.2. Wastewater methane emission abatement
Abatement options for the wastewater sector include the
incremental addition of methane mitigation equipment not
already included in the initial construction of a municipal waste-
water treatment plant, improve existing treatment practices and
use anaerobic digesters [47,134,142–145].
4.2.2.1. Improved wastewater treatment practices. These treatment
practices for domestic and industrial wastewaters include reduc-
tion of the amount of organic waste anaerobically digested.
Storing and treating sludge under aerobic conditions is one of
the measures. Another option is through improved aeration and/
or the scaling back of the use of stagnant settling lagoons. Where
the treatment is carried out anaerobically, the methane generated
could be captured and used as a source of energy for the heating
of the wastewater and sludge digestion tank. Excess methane
could be used for electricity generation with flaring being the last
resort.
4.2.2.2. Anaerobic digesters. Methane from anaerobic process can
be flared or used for cogeneration to reduce methane emissions
from biomass or liquid effluents with high organic content.
5. Conclusions
The study has reviewed the emission of methane from three
major sectors – agriculture, energy and waste. The dangers posed
by continued global warming have been highlighted through the
surface temperature profile over the years. The cause of this
global warming has been traced to anthropogenic activities
through the increased reliance on fossil fuels and forest degrada-
tion. Methane has been found to contribute about 20% to this
global warming. The review has also shown that the largest
sources of anthropogenic methane emissions are agriculture
(53%), energy (28%) and waste (19%). Population increase and
improved living standards, especially in developing economies,
will continue to push these emission values higher in the future.
The abatement and mitigation options that have been identified
and highlighted will go a long way in reducing these emissions or
rechanneling them to other uses and thus safeguard and protect
the environment.
References
[1] Calabr
o PS. Greenhouse gases emission from municipal waste management:
The role of separate collection. Waste Management 2009;29:2178–87.
[2] VijayaVenkataRaman S, Iniyan S, Goic R. A review of climate change,
mitigation and adaptation. Renewable and Sustainable Energy Reviews
2012;16(1):878–97.
[3] Abbasi T, Abbasi SA. Biomass energy and the environmental impacts
associated with its production and utilization. Renewable and Sustainable
Energy Reviews 2010;14(3):919–37.
[4] Bilen K, Ozyurt O, Bakırcı K, Karslı S, Erdogan S, Yılmaz M, et al. Energy
production, consumption, and environmental pollution for sustainable
development: A case study in Turkey. Renewable and Sustainable Energy
Reviews 2008;12(6):1529–61.
[5] Bilgen S, Keles
-S, Kaygusuz A, Sarı A, Kaygusuz K. Global warming and
renewable energy sources for sustainable development: A case study in
Turkey. Renewable and Sustainable Energy Reviews 2008;12(2):372–96.
[6] Naqvi SMK, Sejian V. Global climate change: Role of livestock. Asian Journal
of Agricultural Sciences 2011;3(1):19–25.
[7] Y¨
uksel I. Global warming and renewable energy sources for sustainable
development in Turkey. Renewable Energy 2008;33:802–12 2008;33:802–12.
[8] Russel R. The greenhouse effect and greenhouse gases. Windows to the
Universe: University Corporation for Atmospheric Research; 2007.
[9] Hansen J, Sato M, Kharecha P, Russell G, Lea DW, Siddall M. Climate change
and trace gases. Philosophical Transactions of the Royal Society of London,
Series A 2007;365:1925–54.
[10] Xiaoli C, Ziyang L, Shimaoka T, Nakayama H, Ying Z, Xiaoyan C, et al.
Characteristics of environmental factors and their effects on CH
4
and CO
2
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059–5070 5067
emissions from a closed landfill: An ecological case study of Shanghai.
Waste Management 2010;30:446–51.
[11] IPCC. IPCC guidelines for national greenhouse gas inventories. Vol 1–5
Intergovernmental Panel on Climate Change 2006.
[12] Forster P, Ramaswamy V, Artaxo P, Berntsen T, Betts R, Fahey DW, et al.
Changes in atmospheric constituents and in radiative forcing. In: Solomon
S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL,
editors. Climate change 2007: the physical science basis. Contribution of
Working Group I to the Fourth Assessment Report of the Intergovernmental
Panel on Climate Change. Cambridge, United Kingdom and New York, NY,
USA: Cambridge University Press; 2007.
[13] Talyan V, Dahiya RP, Anand S, Sreekrishnan TR. Quantification of
methane emission from municipal solid waste disposal in Delhi. Resources,
Conservation and Recycling 2007;50:240–59.
[14] Chiu C, Bowling LC, Podest E, Bohn TJ, Lettenmaier DP, Schroeder R, et al. An
integrated approach for estimation of methane emissions from wetlands
and lakes in high latitude regions. Geophysical Research Abstracts 2009;11
EGU2009-6449-1.
[15] Todd RW, Cole NA, Casey KD, Hagevoort R, Auvermann BW. Methane
emissions from southern High Plains dairy wastewater lagoons in the
summer. Animal Feed Science and Technology 2011;166–167(0):575–80.
[16] IPCC. Climate Change 2001: The Scientific Basis. In: Houghton YD JT, Griggs
DJ, Noguer M, van der Linden PJ, Dai X, Johnson CA, Maskell K, editors.
Intergovernmental Panel on Climate Change. United Kingdom: Cambridge;
2001.
[17] IPCC. Climate Change 2007: The Physical Science Basis. Contribution of
Working Group I to the Fourth Assessment Report of the Intergovernmental
Panel on Climate Change. In: Solomon DQ S, Manning M, Chen Z, Marquis
M, Averyt KB, Tignor M, Miller HL, editors. Intergovernmental Panel on
Climate Change. United Kingdom: Cambridge; 2007.
[18] Huang Y, He Q. Study on the status of output and utilization of landfill gas
in China. Journal of Sichuan University of Science and Engineering (Natural
Science Edition) 2008;1:117–20.
[19] Rodrı
´guez R, Lombardı
´a C. Analysis of methane emissions in a tunnel
excavated through Carboniferous strata based on underground coal mining
experience. Tunnelling and Underground Space T echnology 2010;25:456–68.
[20] Mackie KR, Cooper CD. Landfill gas emission prediction using Voronoi
diagrams and importance sampling. Environmental Modelling and Software
2009;24:1223–32.
[21] Lelieveld J, Hoor P, J¨
ockel P, Pozzer A, Hadjinicolaou P, Cammas J-P, et al.
Severe ozone air pollution in the Persian Gulf region. Atmospheric Chem-
istry and Physics 2009;9(4):1393–406.
[22] Wuebbles DJE, Hayhoe K. Atmospheric methane and global change.
Earth-Science Reviews 2002;57:177–210.
[23] Agarwal R, Gupta R, Garg JK. A hierarchical model for estimating methane
emission from wetlands using MODIS data and ARIMA modeling. Journal of
the Indian Society of Remote Sensing 2009;37:473–81.
[24] Li T, Huang Y, Zhang W, Song C. CH
4
MOD
wetland
: A biogeophysical model for
simulating methane emissions from natural wetlands. Ecological Modelling
2010;221:666–80.
[25] Jones SK, Rees RM, Skiba UM, Ball BC. Greenhouse gas emissions from a
managed grassland. Global and Planetary Change 2005;47:201–11.
[26] Cai Y, Liu D, Yao Y, Li J, Qiu Y. Geological controls on prediction of coalbed
methane of No. 3 coal seam in Southern Qinshui Basin, North China.
International Journal of Coal Geology 2011;88(2–3):101–12.
[27] Ozdemir E. Modeling of coal bed methane (CBM) production and CO
2
sequestration in coal seams. International Journal of Coal Geology
2009;77:145–52.
[28] Makhov GA, Bazhin NM. Methane emission from lakes. Chemosphere
1999;38(6):1453–9.
[29] Chang N-B, Qi C, Islam K, Hossain F. Comparisons between global warming
potential and cost–benefit criteria for optimal planning of a municipal solid
waste management system. Journal of Cleaner Production 2012;20(1):1–13.
[30] Mendes P, Santos AC, Perna F, Ribau Teixeira M. The balanced scorecard as
an integrated model applied to the Portuguese public service: a case study
in the waste sector. Journal of Cleaner Production 2012;24(0):20–9.
[31] Raco B, Battaglini R, Lelli M. Gas emission into the atmosphere from
controlled landfills: an example from Legoli landfill (Tuscany, Italy).
Environmental Science and Pollution Research 2010;17(6):1197–206.
[32] Ma J, Xu H, Cai Z. Effect of fertilization on methane emissions from rice
fields. Soils 2010;42(2):153–63.
[33] Yang S-S, Lai C-M, Chang H-L, Chang E-H, Wei C-B. Estimation of methane
and nitrous oxide emissions from paddy fields in Taiwan. Renewable
Energy 2009;34:1916–22.
[34] Zhang L, Yu D, Shi X, Weindorf DC, Zhao L, Ding W, et al. Simulation of
global warming potential (GWP) from rice fields in the Tai-Lake region,
China by coupling 1:50,000 soil database with DNDC model. Atmospheric
Environment 2009;43:2737–46.
[35] Engle MA, Radke LF, Heffern EL, O’Keefe JMK, Smeltzer CD, Hower JC, et al.
Quantifying greenhouse gas emissions from coal fires using airborne
and ground-based methods. International Journal of Coal Geology
2011;88(2–3):147–51.
[36] Karacan CO
¨, Ruiz FA, Cot
e M, Phipps S. Coal mine methane: A review
of capture and utilization practices with benefits to mining safety and
to greenhouse gas reduction. International Journal of Coal Geology
2011;86(2–3):121–56.
[37] Su S, Han J, Wu J, Li H, Worrall R, Guo H, et al. Fugitive coal mine methane
emissions at five mining areas in China. Atmospheric Environment
2011;45(13):2220–32.
[38] Howarth R, Santoro R, Ingraffea A. Methane and the greenhouse-gas
footprint of natural gas from shale formations. Climatic Change
2011;106(4):679–90.
[39] Wang T, Geng A, Li X, Wang H, Wang Z, Qiufen L. A prediction model of oil
cracked gas resources and Its application in the gas pools of Feixianguan
Formation in NE Sichuan Basin, SW China. Journal of Geological Research
2011;2011:11.
[40] Alemu AW, Dijkstra J, Bannink A, France J, Kebreab E. Rumen stoichiometric
models and their contribution and challenges in predicting enteric methane
production. Animal Feed Science and Technology 2011;166-167(0):761–78.
[41] Brown EG, Anderson RC, Carstens GE, Gutierrez-Ban
˜uelos H, McReynolds JL,
Slay LJ, et al. Effects of oral nitroethane administration on enteric methane
emissions and ruminal fermentation in cattle. Animal Feed Science and
Technology 2011;166-167(0):275–81.
[42] Jones FM, Phillips FA, Naylor T, Mercer NB. Methane emissions from grazing
Angus beef cows selected for divergent residual feed intake. Animal Feed
Science and Technology 2011;166-167(0):302–7.
[43] Dong H, Zhu Z, Zhou Z, Xin H, Chen Y. Greenhouse gas emissions from swine
manure storedat different stack heights. Animal Feed Science and Technology
2011;166–167(0):557–61.
[44] Park KH, Jeon JH, Jeon KH, Kwag JH, Choi DY. Low greenhouse gas emissions
during composting of solid swine manure. Animal Feed Science and
Technology 2011;166–167(0):550–6.
[45] Bauer A, B ¨
osch P, Friedl A, Amon T. Analysis of methane potentials of steam-
exploded wheat straw and estimation of energy yields of combined ethanol
and methane production. Journal of Biotechnology 2009;142:50–5.
[46] Wang S, Yang X, Lin X, Hu Y, Luo C, Xu G, et al. Methane emission by plant
communities in an alpine meadow on the Qinghai-Tibetan Plateau: a new
experimental study of alpine meadows and oat pasture. Biology Letters
2009;5:535–8.
[47] Shahabadi MB, Yerushalmi L, Haghighat F. Estimation of greenhouse gas
generation in wastewater treatment plants – Model development and
application. Chemosphere 2010;78:1085–92.
[48] Guisasola A, Sharma KR, Keller J, Yuan Z. Development of a model for
assessing methane formation in rising main sewers. Water Research
2009;43:2874–84.
[49] Etheridge DM, Steele LP, Francey RJ, Langenfelds RL. Historic CH
4
records from
Antarctic and Greenland ice cores, Antarctic firn data, and archived air samples
from Cape Grim, Tasmania. In trends: a compendium of data on global change.
Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory,
U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.; 2002.
[50] GMI. Global Methane Initiative. Underground coal mine methane recovery
and use opportunities, /http://www.globalmethane.org/documents/coal_f
s_eng.pdfS; 2008 [Accessed 08.02.2012] .
[51] USEPA. Global anthropogenic non-CO
2
greenhouse gas emissions: 1990–2020
Office of Atmospheric Programs, Climate Change Division. Washington D.C:
US Environmental Protection Agency; 2006.
[52] McGinn SM, Flesch TK, Harper LA, Beauchemin KA. An approach for
measuring methane emissions from whole farms. Journal of Environmental
Qualilty 2006;35:14–20.
[53] USEPA. Inventory of U.S. greenhouse gas emissions and sinks: 1990–2009.
Washington, DC 20460, USA: U.S. Environmental Protection Agency, EPA
430-R-11-005; 2011.
[54] Aluwong T, Wuyep PA, Allam L. Livestock-environment interactions:
Methane emissions from ruminants. African Journal of Biotechnology
2011;10(8):1265–9.
[55] Steinfeld H, Hoffmann I. Livestock, greenhouse gases and global climate
change. In: Rowlinson P, Steele, M and Nefzaoui, A, editor. International
Conference on Livestock and Global Climate Change 2008, Hammamet,
Tunisia; 2008.
[56] Sejian V, Lal R, Lakritz J, Ezeji T. Measurement and prediction of enteric
methane emission. International Journal of Biometeorology 2011;55(1):
1–16.
[57] Grainger C, Beauchemin KA. Can enteric methane emissions from rumi-
nants be lowered without lowering their production? Animal Feed Science
and Technology 2011;166–167:308–20.
[58] Garcia-Apaza E, Paza ABO, Aranaa I. GHG emissions from enteric fermenta-
tion of livestock in Bolivia: values for 1990–2000 and future projections.
Australian Journal of Experimental Agriculture 2008;4:255–9.
[59] Huarte A, Cifuentes V, Gratton R, Clausse A. Correlation of methane
emissions with cattle population in Argentine Pampas. Atmospheric Envir-
onment 2010;44(23):2780–6.
[60] Karakurt I, Aydin G, Aydiner K. Sources and mitigation of methane
emissions by sectors: A critical review. Renewable Energy 2012;39(1):40–8.
[61] FAO. FAOSTAT, Agricultural Database of the Food and Agriculture Organiza-
tion of the United Nations. Italy: Rome, Italy: Food and Agriculture
Organisation Rome; 2010.
[62] Nayak DR, A TK, Babu YJ, Datta A, Rao VR BR. Methane emission from a
flooded field of Eastern India as influenced by planting date and age of rice
(Oryza sativa L.) seedlings. Agriculture, Ecosystems and Environment
2006;115:79–87.
[63] Xu S, Jaffe PR, Mauzerall DL. A process-based model for methane emission
from flooded rice paddy systems. Ecological Modelling 2007;205:475–91.
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059 –50705068
[64] Minamikawa K, Sakai N. The effect of water management based on soil
redox potential on methane emission from two kinds of paddy soils in
Japan. Agriculture, Ecosystems and Environment 2005;107:397–407.
[65] FAPRI. U.S. and World Agricultural Outlook. Food and Agricultural Policy
Research Institute, Iowa State University, and University of Missouri-
Columbia, Ames, Iowa; 2004.
[66] Johnson KA, Johnson DE. Greenhouse gas inventories from animal agricul-
ture for the United States. International Congress Series 2006;1293:21–8.
[67] Møller HB, Sommer SG, Ahring BK. Biological degradation and greenhouse
gas emissions during pre-storage of liquid animal manure. Journal of
Environmental Quality 2004;33:27–36.
[68] Dong C, Yang Y, Zhang J, Lu X. Gaseous emissions from the combustion of a
waste mixture containing a high concentration of N
2
O. Waste Management
2009;29:272–6.
[69] Koppmann R, von Czapiewski K, Reid JS. A review of biomass burning
emissions, part I: gaseous emissions of carbon monoxide, methane, volatile
organic compounds, and nitrogen containing compounds. Atmospheric
Chemistry and Physics Discussions 2005;5:10455–516.
[70] Keppler F, Hamilton JTG, Braß M, Rockmann T. Methane emissions from
terrestrial plants under aerobic conditions. Nature 2006;439(7073):187–91.
[71] Beauchemin KA, McGinn SM. Methane emissions from beef cattle: Effects of
fumaric acid, essential oil, and canola oil. Journal of Animal Science
2006;84(6):1489–96.
[72] Beauchemin KA, McGinn SM, Martinez TF, McAllister TA. Use of condensed
tannin extract from quebracho trees to reduce methane emissions from
cattle. Journal of Animal Science 2007;85:1990–6.
[73] Beauchemin KA, McGinn SM, Benchaar C. Holtshausen l. Crushed sunflower,
flax, or canola seeds in lactating dairy cow diets: Effects on methane
production, rumen fermentation, and milk production. Journal of Dairy
Science 2009;92:2118–27.
[74] Takahashi J, Mwenya B, Santoso B, Sar C, Umetsu K, Kishimoto T, et al.
Mitigation of methane emission and energy recycling in animal agricultural
systems. Asian-Australasian Journal of Animal Science 2005;18(8):1199–208.
[75] Martin C, Rouel J, Jouany JP, Doreau M, Chilliard Y. Methane output and diet
digestibility in response to feeding dairy cows crude linseed, extruded
linseed, or linseed oil. Journal of Animal Science 2008;86:2642–50.
[76] Beauchemin KA, McGinn SM. Methane emissions from feedlot cattle fed
barley or corn diets. Journal of Animal Science 2005;83:653–66.
[77] Osada T, Takada R, Shinzato I. Potential reduction of greenhouse gas
emission from swine manure by using a low-protein diet supplemented
with synthetic amino acids. Animal Feed Science and Technology
2011;166–167(0):562–74.
[78] Cao Y, Takahashi T, Horiguchi K-i, Yoshida N, Cai Y. Methane emissions from
sheep fed fermented or non-fermented total mixed ration containing
whole-crop rice and rice bran. Animal Feed Science and Technology
2010;157(1–2):72–8.
[79] van Zijderveld SM, Fonken B, Dijkstra J, Gerrits WJJ, Perdok HB, Fokkink W,
et al. Effects of a combination of feed additives on methane production, diet
digestibility, and animal performance in lactating dairy cows. Journal of
Dairy Science 2011;94(3):1445–54.
[80] van Zijderveld SM, Dijkstra J, Perdok HB, Newbold JR, Gerrits WJJ. Dietary
inclusion of diallyl disulfide, yucca powder, calcium fumarate, an extruded
linseed product, or medium-chain fatty acids does not affect methane
production in lactating dairy cows. Journal of Dairy Science 2011;94(6):
3094–104.
[81] DeRamus HA, Clement TC, Giampola DD. Methane emissions of beef cattle
on forages: efficiency of grazing management systems. Journal of Environ-
mental Quality 2003;32:269–77.
[82] Holtshausen L, Chaves AV, Beauchemin KA, McGinn SM, McAllister TA,
Odongo NE, et al. Feeding saponin-containing Yucca schidigera and Quillaja
saponaria to decrease enteric methane production in dairy cows. Journal of
Dairy Science 2009;92(6):2809–21.
[83] Kasuya H, Takahashi J. Methane emissions from dry cows fed grass or
legume silage. Asian-Australasian Journal of Animal Science 2010;23(5):
563–6.
[84] Lascano CE, Ca
´rdenas E. Alternatives for methane emission mitigation in
livestock systems. Revista Brasileira de Zootecnia 2010;39:175–82.
[85] McGinn SM, Chung Y-H, Beauchemin KA, Iwaasa AD, Grainger CM. Use of
corn distillers’ dried grains to reduce enteric methane loss from beef cattle.
Canadian Journal of Animal Science 2009;89(3):409–13.
[86] Vellinga TV, Hovin IE. Maize silage for dairy cows: mitigation of methane
emissions can be offset by land use change. Nutrient Cycling in Agroeco-
systems 2011;89:413–26.
[87] Beauchemin KA, McGinn SM. Reducing methane in dairy and beef cattle
operations: What is feasible? 2009.
[88] Beukes PC, Gregorini P, Romera AJ, Levy G, Waghorn GC. Improving
production efficiency as a strategy to mitigate greenhouse gas emissions
on pastoral dairy farms in New Zealand. Agriculture, Ecosystems and
Environment 2010;136(3-4):358–65.
[89] Leifeld J, Fuhrer J. Greenhouse gas emissions from Swiss agriculture since
1990: implications for environmental policies to mitigate global warming.
Environmental Science and Policy 2005;8:410–7.
[90] Vellinga TV, de Haan MHA, Schils RLM, Evers A, van den Pol–van Dasselaar
A. Implementation of GHG mitigation on intensive dairy farms: Farmers’
preferences and variation in cost effectiveness. Livestock Science
2011;137(1–3):185–95.
[91] Iqbal MF, Cheng Y-F, Zhu W-Y, Zeshan B. Mitigation of ruminant methane
production: current strategies, constraints and future options. World
Journal of Microbiology and Biotechnology 2008;24:2747–55.
[92] Steinfeld H, Hoffmann I. Livestock, greenhouse gases and global climate
change. In: Rowlinson P, Steele M, Nefzaoui A, editors. International
Conference on Livestock and Global Climate Change. Tunisia: Hammamet;
2008 17-20 May, 2008.
[93] Wang J, Duan C, Ji Y, Sun Y. Methane emissions during storage of different
treatments from cattle manure in Tianjin. Journal of Environmental
Sciences 2010;22(10):1564–9.
[94] Sommer SG, Petersen SO, Møller HB. Algorithms for calculating methane
and nitrous oxide emissions from manure management. Nutrient Cycling in
Agroecosystems 2004;69:143–54.
[95] Jicong H, Yanhua X, Fengde W, Renjie D. Greenhouse gas emissions from
livestock waste: China evaluation. International Congress Series
2006;1293:29–32.
[96] Weiske A, Vabitsch A, Olesen JE, Schelde K, Michel J, Friedrich R, et al.
Mitigation of greenhouse gas emissions in European conventional and organic
dairy farming. Agriculture, Ecosystems and Environment 2006;112(2–3):
221–32.
[97] Amjid SS, Bilal MQ, Nazir MS, Hussain A. Biogas, renewable energy resource
for Pakistan. Renewable and Sustainable Energy Reviews 2011;15(6):
2833–7.
[98] Avcio˘
glu AO, T ¨
urker U. Status and potential of biogas energy from animal
wastes in Turkey. Renewable and Sustainable Energy Reviews 2012;16(3):
1557–61.
[99] Dodic
´SN, Popov SD, Dodic
´JM, Rankovic
´JA, Zavargo ZZ, Goluˇ
sin MT.
An overview of biomass energy utilization in Vojvodina. Renewable and
Sustainable Energy Reviews 2010;14(1):550–3.
[100] Lora ES, Andrade RV. Biomass as energy source in Brazil. Renewable and
Sustainable Energy Reviews 2009;13(4):777–88.
[101] Masse
´DI, Talbot G, Gilbert Y. On farm biogas production: A method to
reduce GHG emissions and develop more sustainable livestock operations.
Animal Feed Science and Technology 2011;166–167(0):436–45.
[102] Singh J, Gu S. Biomass conversion to energy in India—A critique. Renewable
and Sustainable Energy Reviews 2010;14(5):1367–78.
[103] Tock JY, Lai CL, Lee KT, Tan KT, Bhatia S. Banana biomass as potential
renewable energy resource: A Malaysian case study. Renewable and
Sustainable Energy Reviews 2010;14(2):798–805.
[104] Boons F, Spekkink W, Mouzakitis Y. The dynamics of industrial symbiosis:
a proposal for a conceptual framework based upon a comprehensive
literature review. Journal of Cleaner Production 2011;19(9–10):905–11.
[105] Costa I, Ferr~
ao P. A case study of industrial symbiosis development using a
middle-out approach. Journal of Cleaner P roduction 2010;18(10-11):984–92.
[106] Costa I, Massard G, Agarwal A. Waste management policies for industrial
symbiosis development: case studies in European countries. Journal of
Cleaner Production 2010;18(8):815–22.
[107] Geng Y, Tsuyoshi F, Chen X. Evaluation of innovative municipal solid waste
management through urban symbiosis: a case study of Kawasaki. Journal of
Cleaner Production 2010;18(10-11):993–1000.
[108] Lehtoranta S, Nissinen A, Mattila T, Melanen M. Industrial symbiosis and the
policy instruments of sustainable consumption and production. Journal of
Cleaner Production 2011;19(16):1865–75.
[109] Taibi E, Gielen D, Bazilian M. The potential for renewable energy in industrial
applications. Renewable and Sustainable Energy Reviews 2012;16(1):735–44.
[110] Chandra R, Takeuchi H, Hasegawa T. Methane production from lignocellulosic
agricultural crop wastes: A review in context to second generation of biofuel
production. Renewable and Sustainable Energy Reviews 2012;16(3):1462–76.
[111] Chen F, Lu S-M, Wang E, Tseng K-T. Renewable energy in Taiwan. Renew-
able and Sustainable Energy Reviews 2010;14(7):2029–38.
[112] Demirbas MF, Balat M, Balat H. Potential contribution of biomass to the
sustainable energy development. Energy Conversion and Management
2009;50(7):1746–60.
[113] Zhao X, He J, Cao J. Study on mitigation strategies of methane emission from
rice paddies in the implementation of ecological agriculture. Energy
Procedia 2011;5(0):2474–80.
[114] Wassmann R, Hosen Y, Sumfleth K Reducing methane emissions from irrigated
rice. /http://www.ifpri.org/sites/default/files/publications/focus16_03.pdfS.
Focus 16, Brief 3; 2009 [accessed 15.02.12].
[115] Shin Y-K, Yun S-H, Park M-E, Lee B-L. Mitigation options for methane
emission from rice fields in Korea. Ambio: A Journal of the Human
Environment 1996;25(4):289–91.
[116] Babu YJ, Nayak DR, Adhya TK. Potassium application reduces methane
emission from a flooded field planted to rice. Biology and Fertility of Soils
2006;42:532–41.
[117] Towprayoon S, Smakgahn K, Poonkaew S. Mitigation of methane and
nitrous oxide emissions from drained irrigated rice fields. Chemosphere
2005;59:1547–56.
[118] Schlagenhauf M, Waltzer S, Jacobs RL, Freitas CJ. Methane from oil and gas
operations—a source of free fuel for on-site generation? Cogeneration &
On-Site Power Production Magazine /http://wwwcosppcom/articles/print/
volume-8/issue-6/features/methane-from-oil-and-gas-operations-a-sour
ce-of-free-fuel-for-on-site-generationhtmlS; 2007 [Accessed 15.01.12].
[119] Franklin P. Methane from coal mines presents opportunity to recover
energy and generate revenues. Coalbed methane outreach program. US
Environmental Protection Agency; 2009.
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059–5070 5069
[120] Wang YH. Coal demand and coal industry development in China. In: 5th
meeting of the Australia–China bilateral dialogue on resources cooperation.
Sydney, Australia; 3 December 2009.
[121] Su S, Adhikary D, Worrall R, Gabeva D. Study on coal mine methane
resources and potential project development CSIRO exploration and mining
report P2009/423; 2009.
[122] Krzysztof W. Harnessing methane emissions from coal mining. Process
Safety and Environmental Protection 2008;86(5):315–20.
[123] Tan Z, Wang S, Ma L. Current Status and Prospect of Development and
Utilization of Coal Mine Methane in China. Energy Procedia 2011;5(0):1874–7.
[124] Fernandez R, Robinson DR Projects that achieve large methane emissions
reductions in oil and gas operations. Oil and gas methane emissions
reduction workshop. Tomsk, Russia; 14–16 September 2005.
[125] Robinson DR, Fernandez R, Kantamaneni R. Methane emissions mitigation
options in the global oil and natural gas industries. 3rd international
methane and nitrous oxide mitigation conference; 2003.
[126] Schultz K. Coal mine-ventilation air methane mitigation: technologies to
harnass an energy and environmental resource. Energeia 2003;14(5):1–3.
[127] Somers JM, Schultz HL. Coal mine methane ventilation air emissions:
new mitigation technologies. 9th Congress on Ventilation Air Methane.
India 2009.
[128] Abushammala MFM, Ahmad Basri NE, Basri H, El-Shafie AH, Kadhum AAH.
Regional landfills methane emission inventory in Malaysia. Waste Manage-
ment & Research 2010.
[129] Bicheldey TK, Latushkina EN. Biogass emission prognosis at the landfills.
International Journal of Environmental Science and Technology 2010;7(4):
623–8.
[130] Wangyao K, Yamada M, Endo K, Ishigaki T, Naruoka T, Towprayoon S, et al.
Methane generation rate constant in tropical landfill. Journal of Sustainable
Energy and Environment 2010;1:181–4.
[131] Jha AK, Sharma C, Singh N, Ramesh R, Purvaja R, Gupta PK. Greenhouse gas
emissions from municipal solid waste management in Indian mega-cities:
a case study of Chennai landfill sites. Chemosphere 2008;71:750–8.
[132] Franchetti MJ. Solid waste analysis and minimization: a systems approach.
New York: McGraw-Hill Company, Inc; 2009.
[133] Shirai Y, Wakisaka M, Yacob S, Hassan MA, Suzuki S. Reduction of methane
released from palm oil mill lagoon in malaysia and its countermeasures.
Mitigation and Adaptation Strategies for Global Change 2003;8:237–52.
[134] El-Fadel M, Massoud M. Methane emissions from wastewater management.
Environmental Pollution 2001;114:177–85.
[135] Asif M. Sustainable energy options for Pakistan. Renewable and Sustainable
Energy Reviews 2009;13:903–9.
[136] Chen Y, Yang G, Sweeney S, Feng Y. Household biogas use in rural China:
A study of opportunities and constraints. Renewable and Sustainable Energy
Reviews 2010;14(1):545–9.
[137] Mekhilef S, Saidur R, Safari A. Mustaffa WESB. Biomass energy in Malaysia:
Current state and prospects. Renewable and Sustainable Energy Reviews
2011;15(7):3360–70.
[138] Singh RP, Tyagi VV, Allen T, Ibrahim MH, Kothari R. An overview for
exploring the possibilities of energy generation from municipal solid waste
(MSW) in Indian scenario. Renewable and Sustainable Energy Reviews
2011;15(9):4797–808.
[139] Gewald D, Siokos K, Karellas S, Spliethoff H. Waste heat recovery from a
landfill gas-fired power plant. Renewable and Sustainable Energy Reviews
2012;16(4):1779–89.
[140] Panwar NL, Kothari R, Tyagi VV. Thermo chemical conversion of biomass—
Eco friendly energy routes. Renewable and Sustainable Energy Reviews
2012;16(4):1801–16.
[141] Zheng YH, Li ZF, Feng SF, Lucas M, Wu GL, Li Y, et al. Biomass energy
utilization in rural areas may contribute to alleviating energy crisis and
global warming: A case study in a typical agro-village of Shandong, China.
Renewable and Sustainable Energy Reviews 2010;14(9):3132–9.
[142] Fine P, Hadas E. Options to reduce greenhouse gas emissions during
wastewater treatment for agricultural use. Science of The Total Environ-
ment 2012;416(0):289–99.
[143] Flores-Alsina X, Corominas L, Snip L, Vanrolleghem PA. Including green-
house gas emissions during benchmarking of wastewater treatment plant
control strategies. Water Research 2011;45(16):4700–10.
[144] Pan T, Zhu X-D, Ye Y-P. Estimate of life-cycle greenhouse gas emissions from
a vertical subsurface flow constructed wetland and conventional waste-
water treatment plants: A case study in China. Ecological Engineering
2011;37(2):248–54.
[145] Pre
´ndez M, Lara-Gonza
´lez S. Application of strategies for sanitation manage-
ment in wastewater treatment plants in order to control/reduce greenhouse
gas emissions. Journal of Environmental Man agement 2008;88(4):658–64.
R.O. Yusuf et al. / Renewable and Sustainable Energy Reviews 16 (2012) 5059 –50705070
