Biomass Energy: Sustainable Solution for Greenhouse Gas Emission A.K.M. Sadrul Islama* and M. Ahiduzzamanb abMechanical & Chemical Engineering Department, Islamic University of Technology, Board Bazar, Gazipur-1704, Bangladesh *Corresponding Author: Email- [email protected] Abstract. Biomass is part of the carbon cycle. Carbon dioxide is produced after combustion of biomass. Over a relatively short timescale, carbon dioxide is renewed from atmosphere during next generation of new growth of green vegetation. Contribution of renewable energy including hydropower, solar, biomass and biofuel in total primary energy consumption in world is about 19%. Traditional biomass alone contributes about 13% of total primary energy consumption in the world. The number of traditional biomass energy users expected to rise from 2.5 billion in 2004 to 2.6 billion in 2015 and to 2.7 billion in 2030 for cooking in developing countries. Residential biomass demand in developing countries is projected to rise from 771 Mtoe in 2004 to 818 Mtoe in 2030. The main sources of biomass are wood residues, bagasse, rice husk, agro-residues, animal manure, municipal and industrial waste etc. Dedicated energy crops such as short-rotation coppice, grasses, sugar crops, starch crops and oil crops are gaining importance and market share as source of biomass energy. Global trade in biomass feedstocks and processed bioenergy carriers are growing rapidly. There are some drawbacks of biomass energy utilization compared to fossil fuels viz: heterogeneous and uneven composition, lower calorific value and quality deterioration due to uncontrolled biodegradation. Loose biomass also is not viable for transportation. Pelletization, briquetting, liquefaction and gasification of biomass energy are some options to solve these problems. Wood fuel production is very much steady and little bit increase in trend, however, the forest land is decreasing, means the deforestation is progressive. There is a big challenge for sustainability of biomass resource and environment. Biomass energy can be used to reduce greenhouse emissions. Woody biomass such as briquette and pellet from un-organized biomass waste and residues could be used for alternative to wood fuel, as a result, forest will be saved and sustainable carbon sink will be developed. Clean energy production from biomass (such as ethanol, biodiesel, producer gas, bio-methane) could be viable option to reduce fossil fuel consumption. Electricity generation from biomass is increasing throughout the world. Co-firing of biomass with coal and biomass combustion in power plant and CHP would be a viable option for clean energy development. Biomass can produce less emission in the range of 14% to 90% compared to emission from fossil for electricity generation. Therefore, biomass could play a vital role for generation of clean energy by reducing fossil energy to reduce greenhouse gas emissions. The main barriers to expansio ...

1. Biomass Energy: Sustainable
Solution
for Greenhouse Gas
Emission
A.K.M. Sadrul Islama* and M. Ahiduzzamanb
abMechanical & Chemical Engineering Department,
Islamic University of Technology, Board Bazar, Gazipur-1704,
Bangladesh
*Corresponding Author: Email- [email protected]
Abstract. Biomass is part of the carbon cycle. Carbon dioxide is
produced after combustion of biomass. Over a
relatively short timescale, carbon dioxide is renewed from
atmosphere during next generation of new growth of
green vegetation. Contribution of renewable energy including
hydropower, solar, biomass and biofuel in total
primary energy consumption in world is about 19%. Traditional
biomass alone contributes about 13% of total

2. primary energy consumption in the world. The number of
traditional biomass energy users expected to rise from 2.5
billion in 2004 to 2.6 billion in 2015 and to 2.7 billion in 2030
for cooking in developing countries. Residential
biomass demand in developing countries is projected to rise
from 771 Mtoe in 2004 to 818 Mtoe in 2030. The main
sources of biomass are wood residues, bagasse, rice husk, agro-
residues, animal manure, municipal and industrial
waste etc. Dedicated energy crops such as short-rotation
coppice, grasses, sugar crops, starch crops and oil crops are
gaining importance and market share as source of biomass
energy. Global trade in biomass feedstocks and processed
bioenergy carriers are growing rapidly. There are some
drawbacks of biomass energy utilization compared to fossil
fuels viz: heterogeneous and uneven composition, lower
calorific value and quality deterioration due to uncontrolled
biodegradation. Loose biomass also is not viable for
transportation. Pelletization, briquetting, liquefaction and
gasification of biomass energy are some options to solve these
problems. Wood fuel production is very much steady
and little bit increase in trend, however, the forest land is
decreasing, means the deforestation is progressive. There is
a big challenge for sustainability of biomass resource and
environment. Biomass energy can be used to reduce
greenhouse emissions. Woody biomass such as briquette and

3. pellet from un-organized biomass waste and residues
could be used for alternative to wood fuel, as a result, forest
will be saved and sustainable carbon sink will be
developed. Clean energy production from biomass (such as
ethanol, biodiesel, producer gas, bio-methane) could be
viable option to reduce fossil fuel consumption. Electricity
generation from biomass is increasing throughout the
world. Co-firing of biomass with coal and biomass combustion
in power plant and CHP would be a viable option for
clean energy development. Biomass can produce less emission
in the range of 14% to 90% compared to emission
from fossil for electricity generation. Therefore, biomass could
play a vital role for generation of clean energy by
reducing fossil energy to reduce greenhouse gas emissions. The
main barriers to expansion of power generation from
biomass are cost, low conversion efficiency and availability of
feedstock. Internationalization of external cost in
power generation and effective policies to improve energy
security and carbon dioxide reduction is important to
boost up the bio-power. In the long run, bio-power will depend
on technological development and on competition for
feedstock with food production and arable land use.
Keywords: Biomass energy, agro-waste and residues, energy
crops, biomass conversion, bio-power, carbon cycle,

4. greenhouse gas emission.
PACS:����88.20.-j;88.05.Np
INTRODUCTION
Energy consumption varies dramatically in different parts of the
world. World average annual
per-capita consumption of modern energy is 1,519 kilograms of
oil equivalent (kgoe).While the average per
capita energy consumption in high-income countries is 5,228
kgoe, in low-income countries it is only 250 kgoe
[1, 2]. Traditional biomass is the only source of energy for the
people of low income countries. The biomass
includes fuel wood, crop residues, and animal wastes [3].
However, world energy demand is increasing due to
the rapid economic development of the developing countries.
Fossil fuel is used to meet the energy demand for
such development. Due to use of fossil fuel green house gas
emissions are rising rapidly. The supply of
sustainable energy is one of the main challenges that mankind
will face over the coming decades, particularly
because of the need to address climate change. Biomass can
make a substantial contribution to supplying future
energy demand in a sustainable way [4]. It is presently the
largest global contributor of renewable energy, and

5. has significant potential to expand in the production of heat,
electricity, and fuels for transport. Biomass is
The 4th International Meeting of Advances in Thermofluids
(IMAT 2011)
AIP Conf. Proc. 1440, 23-32 (2012); doi: 10.1063/1.4704200
© 2012 American Institute of Physics 978-0-7354-1032-
9/$30.00
23
produced by capturing carbon dioxide from air by plant during
photosynthesis process. By combustion process
of biomass the carbon dioxide is released into air that can be
captured by the plant during next growing season.
Therefore, biomass can be renewed after combustion within a
very short time scale. If carefully managed, the
bioenergy could provide an even larger contribution to global
primary energy supply, significant reductions in
greenhouse gas emissions and potentially other environmental
benefits. Bioenergy could provide opportunities
for economic and social development in rural areas. Moreover,

6. there is scope for using wastes and residues,
reducing waste disposal problems and making better use of
resources. Biomass, derived from forestry,
agricultural, and municipal residues as well as from a small
share of crops grown specifically as fuel, is
available as straw or wood chips, vegetable oils and animal
slurries that can be converted to biogas. It is
commonly used to generate both power and heat, generally
through combustion, and some biomass can be
converted to biofuels for transport. Biogas, a byproduct of
fermenting solid and liquid biomass, can be
converted by a combustion engine to heat and power. Recent
increases in biomass use for power production
have been seen in a number of European countries and in some
developing countries.
Global Bioenergy Scenario
At present, the main biomass feedstocks are forestry,
agricultural and municipal residues and wastes for the
generation of electricity and heat. In addition, liquid biofuels
are produced from a very small shares of sugar,
grain, and vegetable oil crops.
The share of renewable energy in global final energy

7. comsumption is 19 percent [5] (Fig. 1). This
renewable energy includes traditional biomass, large
hydropower, and “new” renewables (small hydro, modern
biomass, wind, solar, geothermal, and biofuels). Of this 19
percent, traditional biomass, used primarily for
cooking and heating, accounts for approximately 13 percent and
is growing slowly or even declining in some
regions as biomass is used more efficiently or is replaced by
more modern energy forms.
FIGURE 1. Renewable energy share of global final energy
consumption in 2008 [5]
The predominant use of fuel wood in non-commercial
applications, in simple inefficient stoves for domestic
heating and cooking in developing countries. This traditional
use of biomass is expected to grow with increasing
world population. Among the different source of biomass
energy wood fuel contribute 67% of total biomass
supply (Fig. 2). Wood fuel production is very much steady and
little bit increase in trend, however, the forest
land is decreasing, means the deforestation is progressive
accounted 8.3 million hectare per year [6]. Woody
biomass such as briquette and pellet from un-organized biomass
waste and residues could be used for alternative

8. to wood fuel, as a result, forest will be saved and sustainable
carbon sink will be developed [7]. Clean energy
production from biomass (such as ethanol, biodiesel, producer
gas, bio-methane) could be another viable option
to reduce fossil fuel consumption. There is significant scope to
improve its efficiency and environmental
performance and thereby help reduce biomass consumption and
related impacts.
The biomass supplies some 50 EJ globally, which represents
10% of global annual primary energy
consumption. This is mostly traditional biomass used for
cooking and heating [8,14]. There is significant
potential to expand biomass use by tapping the large volumes of
unused residues and wastes. The use of
conventional crops for energy use can also be expanded, with
careful consideration of land availability and food
demand. In the medium term, lignocellulosic crops (both
herbaceous and woody) could be produced on
marginal, degraded and surplus agricultural lands and provide
the bulk of the biomass resource. In the longer
24

9. term, aquatic biomass (algae) could also make a significant
contribution. Based on this diverse range of
feedstocks, the technical potential for biomass is estimated in
the literature to be possibly as high as 1500 EJ/yr
by 2050, although most biomass supply scenarios that take into
account sustainability constraints indicate an
annual potential of between 200 and 500 EJ/yr (excluding
aquatic biomass). Forestry and agricultural residues
and other organic wastes (including municipal solid waste)
would provide between 50 and 150 EJ/yr, while the
remainder would come from energy crops, surplus forest
growth, and increased agricultural productivity [4].
FIGURE 2. Share of biomass sources in primary bioenergy mix
[4,8]
Without strong new policies to expand access to cleaner fuels
and technologies, the number of people in
developing countries relying on traditional biomass as their
main fuel for cooking will continue to increase as
the global population increases. According to the estimates of
World Energy Outlook (WEO) [14] in the
Reference Scenario, in which no new policies are introduced,
the number rises from 2.5 billion in 2004 to 2.6

10. billion in 2015 and to 2.7 billion in 2030 (Table 1). Residential
biomass demand in developing countries is
projected to rise from 771 Mtoe in 2004 to 818 Mtoe in 2030.
These projections take into account the fuel
substitution and the market penetration of more efficient
technologies that would occur as a result of rising per-
capita incomes, fuel availability and other factors.
TABLE (1). People relying on traditional biomass (million) [14]
Region Year
2004 2015 2030
Sub-Saharan Africa 575 627 720
North Africa 4 5 5
India 740 777 782
China 480 453 394
Indonesia 156 171 180
Rest of Asia 489 521 561
Brazil 23 26 27
Rest of Latin America 60 60 58
Total 2528 2640 2727
Biomass Power Around The World

11. Existing global renewable power capacity reached an estimated
1,230 gigawatts (GW) in 2009. Renewable
energy now comprises about a quarter of global power-
generating capacity (estimated at 4,800 GW in 2009) and
supplies some 18 percent of global electricity production. When
large-scale hydropower is not included,
renewables reached a total of 305 GW. Among all renewables,
global wind power capacity increased the most in
2009, by 38 GW. Hydropower has been growing annually by
about 30 GW in recent years, and solar PV
25
capacity increased by more than 7 GW in 2009. Share of
biomass electricity is 52 GW in 2009 (Fig. 3 and Fig.
4).
An estimated 52 GW of biomass power capacity was in place by
the end of 2009. As of 2007, the United
States accounted for more than 34 percent of electricity from
solid biomass generated in Organization of
Economic Cooperation and Development (OECD) countries,
with a total of 42 Terawatt-hours (TWh). Japan

12. was the OECD’s second largest producer, at 16 TWh, and
Germany ranked third, with 10 TWh [9]. Although
the U.S. market is less developed than Europe’s, by late 2009
some 80 operating biomass projects in 20 states
provided approximately 8.5 GW of power capacity, making the
United States the leading country for total
capacity [10]. Many U.S. coal- and gas-fired power plants are
undergoing partial or even full conversion to
biomass by “co-firing” fuels in conventional power plants [11].
Germany and the United Kingdom also generate
increasing amounts of electricity with solid biomass through co-
firing, and the capacity of biomass-only plants
is rising rapidly across Europe [12]. The region’s gross
electricity production from solid biomass has tripled
since 2001 [13]. By early 2010, some 800 solid biomass power
plants were operating in Europe—burning wood,
black liquor, or other biomass to generate electricity—
representing an estimated 7 GW of capacity. The largest
scale and number of such plants are in the heavily wooded
countries of Scandinavia, but Germany and Austria
have also experienced significant growth in recent years. Most
of this increase in biomass capacity has resulted
from the development of combined heat-and-power (CHP)
plants. Just over half of the electricity produced in
the European Union from solid biomass in 2008 was generated

13. in Germany, Finland, and Sweden. Biomass
accounts for about 20 percent of Finland’s electricity
consumption, and Germany is Europe’s top producer.
Germany increased its generation of electricity with solid
biomass 20-fold between 2002 and 2008, to 10 TWh,
and had about 1,200 MW installed by the end of 2008. By early
2010, bioenergy accounted for 5.3 percent of
Germany’s electricity consumption, making it the country’s
second largest renewable generating source after
wind power. Biomass power has also grown significantly in
several developing countries, including Brazil,
Costa Rica, India, Mexico, Tanzania, Thailand, and Uruguay.
China’s capacity rose 14 percent in 2009 to 3.2
GW, and the country plans to install up to 30 GW by 2020.
India generated 1.9 TWh of electricity with solid
biomass in 2008. By the end of 2009, it had installed 835 MW
of solid biomass capacity fueled by agricultural
residues (up about 130 MW in 2009) and more than 1.5 GW of
bagasse cogeneration plants (up nearly 300 MW
in 2009, including off-grid and distributed systems); it aimed
for 1.7 GW of capacity by 2012. Brazil has over
4.8 GW of biomass cogeneration plants at sugar mills, which
generated more than 14 TWh of electricity in
2009; nearly 6 TWh of this total was excess that was fed into
the grid.

14. FIGURE 3. Share of global electricity from renewable source in
2008 [5]
The use of biogas to generate electricity is on the rise as well,
with production increasing an estimated 7
percent during 2008. Biogas is used for electricity generation
mainly in OECD countries, with some 30 TWh
produced in the OECD in 2008. But a number of developing
countries also produce electricity with biogas,
including Thailand, which nearly doubled its capacity in 2009
to 51 MW, and Malaysia, which is also seeing
significant biogas power expansion. Germany passed the United
States in biogas-generated electricity in 2007
and remained the largest producer in 2009; it is also the world’s
largest generator of electricity from liquid
biomass, at 2.9 TWh in 2007. The number of German biogas
plants increased by 570 in 2009, to nearly 4,700,
26
and associated capacity rose by 280 MW to 1.7 GW; total
domestic production was an estimated 9–12 TWh of

15. electricity. In 2008, the most recent year for which data are
available, the United States generated some 7 TWh
with biogas, followed by the United Kingdom at 6 TWh and
Italy at 2 TWh (Table 2).
FIGURE 4. Capacity of world renewable electricity generation
in 2009 [5]
TABLE (2). Biomass power generation at different locations of
the world [5]
Type of biomass Electricity generation and capacity Year
Country
MW TWh
Solid biomass 42 2007 USA
Solid biomass 16 2007 Japan
Solid biomass 10 2007 Germany
Solid biomass 3200 2009 China
Solid biomass 30000 by 2020 China
Bagasse 1500 2009 India
Bagasse 1700 by 2012 India
Bagasse 4800 14 2009 Brazil
Bagasse 30 2008 OECD countries
Biogas 51 2009 Developing countries
Biogas 280 12 2009 Germany

16. Biogas 7 2008 USA
Biogas 6 2008 UK
Biogas 2 2008
Biomass Conversion Technologies
The use of biomass to produce energy is becoming more and
more frequent as it helps to achieve a
sustainable environmental scenario. However the exploitation of
this fuel source does have drawbacks that need
to be solved. There are some drawbacks of biomass energy
utilization compared to fossil fuels viz:
heterogeneous and uneven composition, lower calorific value
and quality deterioration due to biodegradation.
Pelletization, briquetting, liquefaction and gasification of
biomass energy are the few options to solve some of
those problems.
27
There are many bioenergy routes which can be used to convert
raw biomass feedstock into a final energy
product. Several conversion technologies have been developed

17. that are adapted to the different physical nature
and chemical composition of the feedstock, and to the energy
service required (heat, power, transport fuel).
Upgrading technologies for biomass feedstocks (e.g.
pelletisation, torrefaction and pyrolysis) are being
developed to convert bulky raw biomass into denser and more
practical energy carriers for more efficient
transport, storage and convenient use in subsequent conversion
processes.
The production of heat by the direct combustion of biomass is
the leading bioenergy application throughout
the world, and is often cost-competitive with fossil fuel
alternatives. Technologies range from rudimentary
stoves to sophisticated modern appliances. For a more energy
efficient use of the biomass resource, modern,
large-scale heat applications are often combined with electricity
production in combined heat and power (CHP)
systems.
Different technologies exist or are being developed to produce
electricity from biomass. Co-combustion
(also called co-firing) in coal-based power plants is the most
cost-effective use of biomass for power generation.
Dedicated biomass combustion plants, including municipal solid

18. waste (MSW) combustion plants, are also in
successful commercial operation and many are industrial or
district heating CHP facilities. For sludges, liquids
and wet organic materials, anaerobic digestion is currently the
best-suited option for producing electricity and/or
heat from biomass, although its economic case relies heavily on
the availability of low-cost feedstock. All these
technologies are well established and commercially available.
At present, biomass co-firing in modern coal power plants with
efficiencies up to 45% is the most cost-
effective biomass use for power generation. Due to feedstock
availability issues, dedicated biomass plants for
combined heat & power (CHP), are typically of smaller size and
lower electrical efficiency compared to coal
plants (30%-34% using dry biomass, and around 22% for
municipal solid waste). In cogeneration mode the total
efficiency may reach 85%-90%. Biomass integrated gasification
in gas-turbine plants (BIG/GT) is not yet
commercial, but integrated gasification combined cycles (IGCC)
using black-liquor (a by-product from the pulp
& paper industry) are already in use. Anaerobic digestion to
produce biogas is expanding in small, off-grid
applications. Bio-refineries may open the door to combined,
cost-effective production of bio-chemicals,

19. electricity and biofuels.
There are few examples of commercial gasification plants, and
the deployment of this technology is affected
by its complexity and cost. In the longer term, if reliable and
cost-effective operation can be more widely
demonstrated, gasification promises greater efficiency, better
economics at both small and large-scale and lower
emissions compared with other biomass-based power generation
options. Other technologies (such as Organic
Rankine Cycle and Stirling engines) are currently in the
demonstration stage and could prove economically
viable in a range of small-scale applications, especially for
CHP.
In the transport sector, first-generation biofuels are widely
deployed in several countries, mainly bioethanol
from starch and sugar crops and biodiesel from oil crops and
residual oils and fats. Production costs of current
biofuels vary significantly depending on the feedstock used
(and their volatile prices) and on the scale of the
plant. The potential for further deploying these first generation
technologies is high, subject to sustainable land-
use criteria being met.

20. First-generation biofuels face both social and environmental
challenges, largely because they use food crops
which could lead to food price increases and possibly indirect
land-use change. While such risks can be
mitigated by regulation and sustainability assurance and
certification, technology development is also advancing
for next generation processes that rely on non-food biomass
(e.g. lignocellulosic feedstocks such as organic
wastes, forestry residues, high-yielding woody or grass energy
crops and algae). The use of these feedstocks for
second-generation biofuel production would significantly
decrease the potential pressure on land use, improve
greenhouse gas emission reductions when compared to some
first-generation biofuels, and result in lower
environmental and social risk.
Second-generation technologies, mainly using lignocellulosic
feedstocks for the production of ethanol,
synthetic diesel and aviation fuels, are still immature and need
further development and investment to
demonstrate reliable operation at commercial scale and to
achieve cost reductions through scale-up and
replication. The current level of activity in the area indicates
that these routes are likely to become commercial
over the next decade. Future generations of biofuels, such as

21. oils produced from algae, are at the applied R&D
stage, and require considerable development before they can
become competitive contributors to the energy
markets.
28
TABLE (3): Typical Costs of different Renewable Energy
Technologies [5]
Technology Typical Energy Costs
(U.S. cents/kWh)
Technology Typical Energy Costs
(U.S. cents/kWh)
Power Generation Biofuels
Large hydro 3–5 Ethanol 30–50 cents/liter (sugar)
60–80(gasoline equivalent)
Small hydro 5–12 Biodiesel
40–80 cents/liter

22. (diesel equivalent)
On-shore wind 5–9 Rural Energy
Off shore wind 10–14 Mini-hydro 5–12
Biomass power 5–12 Micro-hydro 7–30
Geothermal power 4–7 Pico-hydro 20–40
Solar PV (module) ––– Biogas digester n/a
Rooftop solar PV 20–50 Biomass gasifier 8 –12
Utility-scale solar PV 15–30 Small wind turbine 15–25
Concentrating solar
thermal power (CSP)
14–18 Household wind
turbine
15–35
Hot Water/
Heating/Cooling
Village-scale mini-
grid

23. 25–100
Biomass heat 1–6
Solar home system 40–60
Solar hot
water/heating
2–20 (household)
1–15 (medium)
Geothermal
heating/cooling
0.5–2
Further development of bioenergy technologies is needed,
mainly to improve the efficiency, reliability and
sustainability of bioenergy chains.
The use of domestic biomass resources can make a contribution
to energy security, depending on which

24. energy source it is replacing. Biomass imports from widely
distributed international sources generally also
contribute to the diversification of the energy mix. However,
supply security can be affected by natural
variations in biomass outputs and by supply-demand imbalances
in the food and forest product sectors,
potentially leading to shortages.
Finally, the cost of different renewable energy technologies is
given in Table 3 [5]. For electricity
generation and heating the biomass is a very competitive
source.
The production of bioenergy can also result in other (positive
and negative) environmental and
socioeconomic effects. Most of the environmental effects are
linked to biomass feedstock production, many of
which can be mitigated through best practices and appropriate
regulation. Technical solutions are available for
mitigating most environmental impacts from bioenergy
conversion facilities and their vehicle fleets such as city
buses have historically been diesel powered but are very
suitable for the introduction of new fuels, e.g. biogas or
ethanol.

25. 29
Environmental Issues: Global Carbon Emissions
The history and projection of world energy-related carbon
dioxide emissions are given in Table 4 [15]. It
rises from 29.7 billion metric tons in 2007 to 33.8 billion metric
tons in 2020 and 42.4 billion metric tons in
2035—an increase of 43 percent over the projection period.
With strong economic growth and continued heavy
reliance on fossil fuels expected for most non-OECD economies
under current policies, much of the projected
increase in carbon dioxide emissions occurs among the
developing non-OECD nations. In 2007, non-OECD
emissions exceeded OECD emissions by 17 percent; in 2035,
they are projected to be double OECD emissions.
A significant degree of uncertainty surrounds any long term
projection of energy-related carbon dioxide
emissions. Major sources of uncertainty include estimates of
energy consumption in total and by fuel source.
TABLE (4). World energy-related carbon dioxide emissions by
region, 1990-2035 [15]

26. (billion metric tons)
History Projections Average annual
percentage change
Region 1990 2007 2015 2020 2025 2030 2035 1990-
2007
2007-
2035
OECD 11.5 13.7 13.0 13.1 13.5 13.8 14.2 1.0 0.1
North America 5.8 7.0 6.7 6.9 7.2 7.4 7.7 1.1 0.3
Europe 4.2 4.4 4.1 4.0 4.0 4.1 4.1 0.3 -0.2
Asia 1.6 2.3 2.1 2.2 2.3 2.3 2.4 2.1 0.2
Non-OECD 10.0 16.0 18.5 20.7 23.0 25.5 28.2 2.8 2.0
Europe and Eurasia 4.2 2.9 2.9 2.9 3.0 3.0 3.2 -2.2 0.3
Asia 3.7 9.4 11.2 13.0 14.9 16.9 19.0 5.7 2.5
Middle East 0.7 1.5 1.9 2.1 2.3 2.5 2.7 4.6 2.1
Africa 0.7 1.0 1.2 1.2 1.3 1.5 1.6 2.6 1.7
Central and South
America
0.7 1.2 1.3 1.4 1.5 1.6 1.7 3.1 1.4

27. Total World 21.5 29.7 31.5 33.8 36.5 39.3 42.4 1.9 1.3
Reduction of Ghg Emission by Bioenergy
Bioenergy cycles reduce the carbon emissions by replacing the
fossil fuels energy. The reduction of carbon
emissions depend on how efficient the generation technology is
and how much fossil fuel is used to produce the
biomass. Table 5 gives an approximate values for the carbon
emissions of selected technologies [16]. Biomass
sources produce much less emissions than fossil fuels. Among
the vast area of biomass sources, a few are
discussed below.
TABLE (5). Approximate Carbon Emissions from Sample
Biomass and Conventional Technologies [16]
Fuel and Technology Generation
Efficiency
Grams of CO2 per kWh
diesel generator 20 % 1320

28. coal steam cycle 33% 1000
natural gas combined cycle 45% 410
biogas digester and diesel generator
(with 15% diesel pilot fuel )
18% 220
biomass steam cycle
(biomass energy ratio*= 12)
22% 100
biomass gasifier and gas turbine
(biomass energy ratio*= 12)
35% 60
*The energy of the biomass produced divided by the energy of
the fossil fuel consumed to produce the biomass.
Production of ethanol from sugar cane is energy-efficient since
the crop produces high yields per hectare
and the sugar is relatively easy to extract. If bagasse is used to
provide the heat and power for the process, and

29. 30
ethanol and biodiesel are used for crop production and
transport, the fossil energy input needed for each ethanol
energy unit can be very low compared with 60%-80% for
ethanol from grains. As a consequence, ethanol well-
to wheels CO2 emissions can be as low as 0.2-0.3 kgCO2/litre
ethanol compared with 2.8 kg CO2/litre for
conventional gasoline (90% reduction). Ethanol from sugar beet
requires more energy input and provides 50%-
60% emission reduction compared with gasoline.
Ethanol production from cereals and corn (maize) can be even
more energy-intensive and debate exists
on the net energy gain. Estimates, which are very sensitive to
the process used, suggest that ethanol from maize
may displace petroleum use by up to 95%, but total fossil
energy input currently amounts to some 60%-80% of
the energy contained in the final fuel (20% diesel fuel, the rest
being coal and natural gas) and hence the CO2
emissions reduction may be as low as 15%-25% vs. gasoline.
Ethanol from ligno-cellulosic feedstock – At present, the total

30. energy input needed for the production
process may be even higher as compared to bioethanol from
corn, but in some cases most of such energy can be
provided by the biomass feedstock itself. Net CO2 emissions
reduction from ligno-cellulosic ethanol can
therefore be close to 70% vs. gasoline, and could approach
100% if electricity co-generation displaced gas or
coal-fired electricity. Current R&D aims to exploit the large
potential from improving efficiency in enzymatic
hydrolysis. Energy input and overall emissions for biodiesel
production also depend on feedstock and
process. Typical values are fossil fuel inputs of 30% and CO2
emission reductions of 40%-60% vs. diesel. Using
recycled oils and animal fats reduces the CO2 emissions.
Municipal solid waste (MSW) also offers net reduction of CO2
emissions. MSW can generate some 600
kWh of electricity per tonne and emit net 220-440 kg CO2 from
the combustion of the fossil-derived materials
(20-40% of MSW). The CO2 emitted to generate 600 kWh from
coal would be some 590 kg. Methane emissions
from MSW in modern landfills would be between 50-100 kg/t
(equivalent to 1150-2300 kg CO2), 50% of which
is collected and 50% is released in the atmosphere. Thus,
electricity production from MSW offers a net emission

31. saving between 725 and 1520 kg CO2/t MSW. Saving is even
higher for CHP.
Rice husk, a milling by-product of rice, is used as a source of
thermal energy to produce steam for
parboiling of raw rice. The rice is mostly dried on a concrete
floor under the sunshine. In mechanical drying,
rice husks are used as a source of primary energy. In
Bangladesh, the annual estimated energy used in 2000 for
the drying of rice by sunshine was 10.7 million GJ and for
drying and parboiling by rice husks it was 48.2
million GJ. These amounts will increase to 20.5 and 92.5
million GJ in 2030, respectively. Electrical energy
consumption for mechanical drying and milling of rice was
calculated as 1.83 million GJe and 3.51 million GJe
in 2000 and in 2030, respectively. Biogenic carbon dioxide
emission from burning of rice husk is renewed every
year by the rice plant. Both the biogenic and non-biogenic
carbon dioxide emissions in 2000 were calculated as
5.7 and 0.4 million tonnes, respectively, which will increase to
10.9 and 0.7 million tonnes in 2030. The demand
of energy for rice processing increases every year, therefore,
energy conservation in rice processing industries
would be a viable option to reduce the intensity of energy by
increasing the efficiency of rice processing

32. systems which leads to a reduction in emissions and an
increased supply of rice husk energy to other sectors as
well [17].
The net GHG impact of various biofuels is given in Table 6
[18]. Cellulosic ethanol and sugarcane ethanol
are more effective at displacing GHG emissions ( 90%
reduction) than soy or rape biodiesel ( 50% reduction),
which are in turn more effective at displacing GHG emissions
than corn ethanol, which is itself only marginally
lower in GHGemissions than gasoline (<20% reduction).
TABLE (6). Estimates of net GHG reductions and land
requirements for various biofuel options [18]
GHG
reductions
relative to
gasoline/
diesel vehicle
Yield per
hectare
(liters fuel/ha)

33. Hectares
required to fuel
one car (ha/car)
Ethanol (corn) 14% 3463 1.1
Ethanol
(cellulosic)
88% 5135 0.7
Ethanol
(sugarcane)
91% 6307 0.6
Biodiesel (soya) 40% 5444 4.3
Biodiesel (rape) 50% 1200 2.0
31
Land suitable for producing biomass for energy can also be used
for the creation of biospheric carbon sinks.

34. Several factors determine the relative attractiveness of these
two options, in particular land productivity,
including co-products, and fossil fuel replacement efficiency.
Also, possible direct and indirect emissions from
converting land to another use can substantially reduce the
climate benefit of both bioenergy and carbon sink
projects, and need to be taken into careful consideration. A
further influencing factor is the time scale that is
used for the evaluation of the carbon reduction potential: a short
time scale tends to favour the sink option, while
a longer time scale offers larger savings as biomass production
is not limited by saturation but can repeatedly
(from harvest to harvest) deliver greenhouse gas emission
reductions by substituting for fossil fuels. Mature
forests that have ceased to serve as carbon sinks can in principle
be managed in a conventional manner to
produce timber and other forest products, offering a relatively
low GHG reduction per hectare. Alternatively,
they could be converted to higher yielding energy plantations
(or to food production) but this would involve the
release of at least part of the carbon store created.
Conclusions
The bioenergy plays a dominant role in the developing countries

35. that needs to be modernized in terms of
efficiency, emission and cost. The modern bioenergy has rapidly
expanded over the past decade and is poised to
become a major contributor to global commercial energy
supplies. As with other potentially attractive renewable
energy sources, biomass energy has a definite contribution to
make a sustainable development especially in
terms of GHG emission. The ability of this energy depends on
how it is produced, converted, and used.
Among the OECD (developed) countries Germany, UK, Japan,
USA have emphasized on the use of
bioenergy in place of fossil fuel and thus targeted to reduce
GHG emission. Among the non-OECD counties
notable initiative is taken by China, India, Brazil and Thailand.
As of 2009, the biomass electricity generation
was 52 GW among the total renewable energy power of 1,230
GW which is about 25% of global power
generating capacity. The main barriers to widespread use of
biomass for power generation are cost, low
conversion efficiency and feedstock availability.
Several bioenergy options have great potential in terms of
reduction of GHG emission. Biofuel, MSW, rice
husk, agro-residues etc can contribute in the commercial energy

36. sector and thus reduce the GHG emission.
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32
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