Energy and the New Reality, Volume 2:
C-Free Energy Supply
Chapter 4: Biomass Energy
L. D. Danny Harvey
harvey@geog.utoronto.ca
Publisher: Earthscan, UK
Homepage: www.earthscan.co.uk/?tabid=101808
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From the Summary For Policymakers of the WG1 Report for the
IPCC 5th Assessment Report
Table of agreements and disagreements
among bioenergy experts
Agreements
Disagreements
Improving the efficiency of traditional uses of
bioenergy has both climate and socioeconomic
benefits
The impact of net social livelihoods of large-scale
bioenergy deployment for the global poor is
disputed
The use of waste and residues, in many cases, can
help reducing GHG emissions
The fraction of residues that can be sustainably
removed is disputed
When bioenergy can be used to improve
unproductive, or even toxic, marginal lands, this
aids the reduction of GHG emissions and does
not interfere with food production
The area (amount) of land that is marginal, and not
informally supporting livelihoods or being
biodiversity rich, is not well known
Life-cycle analysis of bioenergy needs to include net
emissions from soil, processing, direct and
indirect effects of land use (change) as well as
biophysical factors, such as albedo.
The boundaries of analysis are disputed (e.g. inclusion
of market-mediated effects, consideration of
time frames, climate forcing factors,
counterfactuals, etc.)
Table of agreements and disagreements (continued)
Agreements
Disagreements
The large-scale use of grain-based and oil-seed
food crops for bioenergy production has at
best low mitigation effects and may cause
net warming, in addition to interfering
possibly harmfully with food production
and increasing environmental harm from
agrochemical use.
The full life-cycle impacts of most bioenergy
production systems are disputed, including
those of energy crops
The total resource potential for bioenergy is
approximately 100-900 EJ per year in 2050.
The maximum sustainable potential for
bioenergy is disputed, with some
researchers estimating it to be only around
160-270 EJ per year in 2050.
Global use of different energy sources for
residential and commercial buildings in 2010
35
Residential buildings
Commercial buildings
Global Energy Use in 2010 (EJ)
30
25
20
15
10
5
0
Electricity
Fossil fuels
District heat
Source: International Energy Agency, Energy Balances Reports for 2010
Biofuels
Figure 4.1 Uses of biomass for energy in 2007. Overall
contribution: about 10% of total primary energy supply.
Source: Sims (2010, in Industrial Crops and Uses, CABI, Wallingford, UK)
Figure 4.2a Trends in biomass use by type, with
uncertainty bars for the total
Biofuel Consumption (Mt/yr)
4000
Industrial
Biofuels
Domestic
Charcoal
Domestic
Dung
Domestic
Crops
Domestic
Fuelwood
3000
2000
1000
0
1900
1925
1950
Year
1975
2000
Figure 4.2b Trends in biomass use by region
3000
North
America
Latin
America
Western
Europe
Eastern
Europe/FSU
Africa
Biofuel Consumption (Mt/yr)
2500
2000
1500
South Asia
East Asia
1000
Southeast
Asia
Oceania
500
0
1900
1925
1950
Year
1975
2000
Advantages of biomass:
•
•
•
•
•
Can be stored
Provides rural income & employment
Potentially cleaner than coal for most pollutants
Can be irrigated and fertilized with sewage water
Can be cultivated in such a way as to improve
the landscape and remediate soils
• Can make use of animal wastes and agricultural
residues while providing an effective fertilizer
byproduct
Disadvantages of biomass energy
• Land intensive (efficiency of photosynthesis is
~ 1%, with further losses when biomass is
converted to secondary forms of energy)
• Can compete with land for food
• Complex to initiate and manage
• Must be tailored to the biophysical and socioeconomic circumstances of each region
Comparison with fossil fuels
• Heating value ranges from 14 GJ/t (sugar cane,
straw) to 18-20 GJ/t (air-dried wood), compared
to 28-31 GJ/t for coal
• This makes biomass bulky and more expensive
to transport (in both dollar and energy terms)
than coal
Table 4.3: Biomass energy resource categories
Source: Hoogwijk (2003, Biomass and Energy, 25, 119-133)
Bioenergy Crops
• Annuals
• Perennial grasses
• Woody Crops (trees)
Annuals
• Starch-rich crops (maize (corn), wheat,
potatoes) (used to produce ethanol)
• Sugar-rich crops (sugarcane, sugar beets)
(used to produce ethanol)
• Oil-rich crops (coconut oil, palm oil,
sunflower oil) (used to produce biodiesel)
Figure 4.3a Sugarcane (a sugar-rich crop)
Source: www.wikipedia.org
Figure 4.3b Sugarcane harvesting
Source: www.wikipedia.org
Figure 4.3c Cut sugarcane stalks
Source: www.wikipedia.org
Figure 4.4 Palm oil (and oil-rich crop)
Sources: Left, Photo by Jeff McNeely in Howarth and Bringezu (2009, Biofuels: Environmental Consequences and
Interactions with Changing Land Use, SCOPE); upper right, Stone (2007, Science, vol 317, pp149 );
lower right, Koh and Wilcove (2007, Nature, vol 448, pp993–994)
Perennial grasses
• Switchgrass (Panicum virgatum)(native to North
America)
• Miscanthus (native to tropical Africa and tropical
and temperate Asia)
• Napier grass (native to tropical Africa)
• Jatropha curcas (a poisonous weed native to
Central America, used in India)
Figure 4.5 Switchgrass (Panicum virgatum)
Source: US Gov public domain
Figure 4.6 Miscanthus sinensus (upper)
& Napier grass (Pennisetum pupureum) (lower)
Source: www.wikipedia.org
Figure 4.7 Close-up of Jatropha (left), and degraded land
before (upper right) and after being planted
with Jatropha (lower right) in India
Source: Left, photo by Jeff McNeely in Howarth and Bringezu (2009, Biofuels: Environmental Consequences and
Interactions with Changing Land Use, SCOPE); right, Fairless (2007, Nature, vol 449, pp652–655)
Woody crops
• Short-rotation coppicing
- Willow (Salix)
- Poplar (Populus)
• Modified conventional forestry
- Acacia (N-fixing)
- Pine (Pinus)
- Eucalyptus
Figure 4.8 Harvest of coppice willow and irrigation
of new growth with sewage water in Sweden.
Source: Dimitriou and Aronsson (2003, Unasylva 56, 221, 47-50)
Figure 4.9a Five-year old Acacia plantation
Source: Doug Maquire, Oregon State University, www.forestryimages.org
Figure 4.9b Eucalyptus plantation in Spain (left) and 4-year
old Eucalyptus in Hawaii (right).
Source: NREL Photo Exchange, www.nrel.gov/data/pix)
Figure 4.9c 14-year old loblolly pine
(Pinus taeda) in Georgia, USA
Source: Dennis Haugen, www.forestryimages.org
Yields of bioenergy crops
• Annuals
- Sunflower
1.5 t/ha/yr
- Maize:
4 t/ha/yr
- Sugarcane, sugar beet:
60 t/ha/yr
• Grasses
- Jatropha:
10-15 t/ha/yr
- Miscanthus
10-15 t/ha/yr
- Switchgrass
10-25 t/ha/yr
- Napier grass
30 t/ha/yr
• Trees
- Loblolly pine:
4-5 t/ha/yr
- Poplar, willow:
10-20 t/ha/yr
- Eucalyptus:
10-50 t/ha/yr
Agricultural Residues
• A variety of residues (stalks, shells, husks,
leaves) from a wide variety of crops (such as
coconut, maize, cotton, groundnuts, pulses, rice,
sugarcane) are produced and used for
household energy use in rural areas of
developing countries already
• Straw is co-fired with coal in Denmark
• Bagasse is a fibrous residue produced during
the processing of sugarcane into sugar
Figure 4.10 Bagasse, a residue from
processing of sugarcane
Source: Warren Gretz and DOE/NREL
Source: Kartha and Larson (2000, Bioenergy
Primer, Modernized Biomass Energy for
Sustainable Development, United Nations
Development Programme, New York)
Forestry residues
• Primary (left in the field): From thinning of
plantations and trimming of felled trees
• Secondary (produced during processing):
Sawdust, bark, wood scraps from production of
marketable wood; bark and black liquor from the
production of pulp for paper
Processes of extracting energy
from biomass
• Direct combustion
• Pyrolysis (heat to 300-500ºC in near absence of air)
• Thermo-chemical gasification (initial pyrolysis, then
heating to 800ºC under pressure)
• Anaerobic digestion
• Fermentation of non-woody biomass
• Hydrolysis & fermentation of woody biomass
• Transesterification of vegetable oils
• Gasification and catalytic production of Fischer-Tropsch
liquids
• Gasification to produce hydrogen
Direct combustion
• Cooking with firewood in developing countries,
typical cook-stove efficiency is 10-20%, 30-60%
with improved stoves (vs. 45-60% with gaseous
fuels)
• Pellet heating, central Europe in particular
• District heating in Sweden, Atlantic Canada
• Issues include ash content (which is related to
the non-combustible silica in the biomass, which
can be high) and K and Ca in the fuel, which can
cause agglomeration in boilers
Figure 4.11 Traditional wood-burning stove (upper), improved
wood-burning stove (middle), and
charcoal-burning stove (lower) in Kenya
Source: Bailis et al (2003, Environmental Science & Technology 37, 2051–2059)
Figure 4.12 A wood-burning hearth in China and its
replacement with a biogas-fueled stove
Source: Kartha and Larson (2000, Bioenergy Primer, Modernized Biomass Energy for
Sustainable Development, United Nations Development Programme, New York)
80
80
70
70
60
60
50
50
40
40
Stove Efficiency
30
30
20
20
Stove Capital Cost
10
10
0
Stove Capital Cost ($)
Stove Efficiency (%)
Figure 4.13 Cookstove efficiency and cost
0
Increasing Affluence
Source: Kammen et al (2001, Policy Discussion Paper for the United Nations Development Program, Environmentally
Sustainable Development Group (ESDG) and the Climate Change Clean Development Mechanism (CDM))
Figure 4.14 Biomass pellets (left) and
pneumatic delivery by truck (right)
Figure 4.15 Pellet-burning stove (left) and furnace
(right)
Source: www.harmonstoves.com
Figure 4.16 Fuel sources for Swedish district heating
70
Heat Produced (TWh/yr)
60
50
Waste Heat
Heat Pumps
Electric Boilers
Biofuels
Coal
Natural Gas
Oil
40
30
20
10
0
1980
1985
1990
1995
Year
Source: Swedish Energy Agency (2008, Energy
in Sweden 2008, www.stem.se)
2000
2005
Thermo-chemical gasification
• Step one: Heat biomass to a temperature of 300-500°C in the near
absence of air to drive off the easily vaporized or volatile materials a process called pyrolysis
• Step two: heat the remaining residue (char) to 850-900°C in the
presence of steam
• Step one produces a mixture of CO, H2, CH4, and CO2 (the first 3 of
which have energy value)
• The gases contain about 2/3 of the energy content of the fuel, which
is lost if they are not captured (as is the case in the production of
charcoal). If captured, the gases can be used for heating, cooking,
generation of electricity, or for cogeneration of useful heat and
electricity.
• Conversely, the gases can be shifted to consist almost entirely of
H2, or can be used to synthesize methanol, dimethyl ether, or
Fischer-Tropsch liquids (all of which are potential transportation
fuels)
• There were no large-scale commercial thermo-chemical gasificationof-biomass facilities anywhere as of early 2006
Figure 4.17a Proportion of original coal and
cellulose remaining as solid residues as they are
heated in the absence of air (pyrolysis)
Fraction of weight remaining
1
0.9
0.8
Coal
0.7
0.6
0.5
0.4
Cellulose
0.3
0.2
0.1
100
300
500
700
900
Temperature (oC)
Source: Larson (1993, Annual Review of Energy and Environment 18, 567–630)
Gasification rate (percent per minute)
Figure 4.17b Rate at which the solid residues (char) from
pyrolysis are converted to gas in the presence of steam
40
Poplar
30
Willow
20
Pine
10
Coal
0
500
600
700
800
900
1000
Temperature oC
Source: Larson (1993, Annual Review of Energy and Environment 18, 567–630)
Figure 4.18 Updraft fixed-bed gasifier (left) and
downdraft fixed-bed gasifier (right).
Source: Kartha and Larson (2000, Bioenergy Primer, Modernized Biomass Energy for
Sustainable Development, United Nations Development Programme, New York)
Biological gasification
(anaerobic digestion)
• Occurs in sanitary landfills (in which waste
including organic matter alternates with clay
layers, creating anaerobic conditions and
temporarily trapping any methane produced
from anaerobic decomposition)
• The methane is extracted with perforated pipes
• The efficiency (heating value of extracted
methane over heating value of the organic waste
is only ~ 20%)
• Can be done with greater efficiency (50-55%) in
dedicated digesters
Figure 4.19 Collection of biogas
from a municipal landfill
Source: Ramage and Scurlock (1996, Renewable Energy, Power for a Sustainable Future,
Oxford University Press, Oxford, 137-182)
Figure 4.20 Dedicated anaerobic digestion
of organic solid waste with recovery of biogas, low- &
high-temperature heat, and digestate as fertilizer
0.085 t of rejects
for dumping
Gas treatment
0.040 t ferrous
metals
1 t refuse 62.5% dry matter
50% organic matter
biogas
125 m3
biogas
Preparation
Methanization
0.875 t
crushed
material
Refining
digestate
0.156 t
combustible
rejects
Combustion
Recovery of
low-temp heat
kWh
low-temperature heat
kWh
high-temperature heat
Source: Ramage and Scurlock (1996, Renewable Energy, Power for a Sustainable Future,
Oxford University Press, Oxford, 137-182)
Anaerobic digestion of animal
and sewage wastes
• 5 million household cattle-dung digesters in
China, 500 large-scale digesters at pig farms
and other agro-industrial sites, and 24,000
digesters at sewage treatment plants
• 20 million households in China use biogas from
digesters for cooking and lighting needs, and 4
million households in India
• 5000 digesters in industrialized countries,
primarily at livestock processing facilities and
municipal sewage treatment plants
Figure 4.21 Cattle dung digester in India
Source: Kartha and Larson (2000, Bioenergy Primer, Modernized Biomass Energy for
Sustainable Development, United Nations Development Programme, New York)
Figure 4.22 Digester on a pig farm in England
Source: Unknown
Figure 4.23a Indian digester design
Source: Kartha and Larson (2000, Bioenergy Primer, Modernized Biomass Energy for
Sustainable Development, United Nations Development Programme, New York)
Figure 4.23b Chinese digester design
Source: Kartha and Larson (2000, Bioenergy Primer, Modernized Biomass Energy for
Sustainable Development, United Nations Development Programme, New York)
Anaerobic digestion of animal
wastes in Denmark
• 20 centralized plants and 35 farm-scale plants,
making it one of the leading industrialized
countries in the world
• The residue is an effective fertilizer
• Yet, these plants process only 3% of the manure
produced in Denmark
• Processing of 50% of the available manure
would allow the complete elimination of oil for
heating and of coal for electricity generation
Production of ethanol by fermentation
of non-woody biomass
• Fermentation requires an input rich in sugars
• Sugarcane is rich in sucrose sugar (a
combination of glucose and fructose)
• Potatoes, corn, and wheat contain starch, which
consists of long chains of glucose molecules
• Initial processing is required to break starch into
its constituent sugars before fermentation can
occur – this occurs as either wet milling (the
grains with starch are soaked in water) or dry
milling (the grains are simply ground down)
• New facilities are based on dry milling
Production of ethanol by hydrolysis and
fermentation of woody biomass
• Woody biomass is called lignocellulosic biomass
• It is a mixture of cellulose (35-50%),
hemicellulose (20-35%), and lignin (12-20%)
• Cellulose consists of long chains of glucose
sugars (it is a polysaccharide)
• Hemi-cellulose consists of short, highly
branched chains of sugars, mainly xylose (a 5carbon sugar) but also arabinose (5-C),
galactose, glucose, and mannose (all 6-C)
• Lignin is a resistant heterogeneous substance
Table 4.8 Typical composition of different ligno-cellulosic biomass
materials, with the sugars composing cellulose and hemi-cellulose
and their identification as 5-carbon (5C) or 6-carbon (6C) sugars.
Cellulose
Glucan (6C)
Hemicellulose
Xylan (5C)
Arabinan (5C)
Galactan (6C)
Mannan (6C)
Lignin
Ash
Acids
Extractives
Heating value (GJHHV/tonnedry)
Hardwoods
EucaHybrid
lyptus
poplar
49.5
44.7
13.1
10.7
0.3
0.8
1.3
27.7
1.3
4.2
4.3
19.5
18.6
14.6
0.8
1.0
2.2
26.4
1.7
1.5
7.1
19.6
Softwood
Pine
Corn
stover
44.56
37.4
Grass
Switchgrass
32.0
21.9
6.3
1.6
2.6
11.4
27.7
0.3
2.7
2.9
19.6
27.5
21.1
2.9
1.9
1.6
18.0
5.8
3.2
8.1
14.9
25.1
21.1
2.8
1.0
0.3
18.1
6.0
1.2
17.5
18.6
Source: Hamelinck et al (2005, Biomass and Bioenergy 28, 384-410), except for corn stover,
which is from Sheehan et al (2004, Journal of Industrial Ecology 7, 117–146)
Steps in making ethanol from woody biomass
• Pretreatment (grinding, following by chemical, physical,
or biological removal of lignin)
• Breakdown of cellulose – addition of water (hydrolysis) in
a weak or strong acid, followed by breakdown with
enzymes that are produced by organisms living on about
2% of the material
• Fermentation – ethanol is readily produced from 6carbon sugars, but no naturally-occurring organisms
convert 5-carbon sugars to ethanol
• Concentration of ethanol through distillation
Figure 4.24 Integrated production of ethanol, heat
and electricity from lignocellulosic biomass
Source: Wyman (1999, Annual Review of Energy and the Environment 24, 189–226)
Biodiesel from vegetable oils
• Vegetable oils almost always contain triacylglycerols
(a glycerol with three fatty acid esters)
• Transesterification is the process of heating a
mixture of 80-90% oil and 10-20% alcohol (typically
methanol or ethanol) in the presence of a catalyst
• The products are methyl or ethyl esters and glycerin
(C3H8O3)
• The methyl or ethyl esters can be burned in a diesel
engine (unlike the original vegetable oils), while
glycerin is used in the cosmetics, ink, lubrication and
preservatives industries and is an ingredient in soap
Biodiesel (continued)
• The major exporters of vegetable oils are
Malaysia, Indonesia, Philippines, Brazil and
Argentina, with palm oil the dominant crop from
these countries used for biodiesel
• Biodiesel in Europe is largely made from
rapeseed oil, while biodiesel in the US is largely
made from soybeans
Production of Biodiesel from oily algae
• The idea is to grow algae in ponds in the desert
(with water transported in, or waste or brackish
water used) to make biodiesel
• Water requirements per litre of biodiesel would
be less than from traditional oilseed crops
• CO2 from nearby powerplants could be
captured, fed to the algae and sequestered by
the algae (by becoming part of the algal mass)
Biodiesel from algae (continued)
• The cancelled US Aquatic Species Program had
concluded that yields of 142,000 litres/ha/yr (4650
GJ/ha/yr) were possible – compared to only 6000
litres/ha/yr from palm oil in Malaysia
• A more recent privately-funded assessment concluded
that yields of about 100,000 litres/ha/yr could be
achieved
• This requires a two stage process: first, growing the
algae to high mass with a projected photosynthetic
efficiency of 5%, then stressing the algae to induce
conversion of 35% of the algae mass to oil with
continued growth at a projected photosynthetic
conversion efficiency of 20%, the latter having been
obtained only for short periods of time (typical
photosynthesis efficiencies for plants are ~ 1% or less)
Biodiesel from algae (continued)
• There seem to be lots of potential practical programs
that could render the idea uneconomic
• Nevertheless, ExxonMobile announced in 2009 that it
will spend up to $600 million over 5-6 years developing
the technology (with the funding level dependent on
results), and other private companies are also working in
this technology
Table 4.9 Average and maximum measured yields from a microalgae bioreactor-pond system. Projected yields are speculative.
Dry biomass (t/ha/yr)
Energy in biomass (GJ/ha/yr)
Energy in oil (GJ/ha/yr)
Measured
Average
Maximum
38
92
763
1836
422
1014
Projected
200
4100
3200
Source: Huntley and Redalje (2007, Mitigation and Adaptation Strategies for Global Change 12,
573–608)
Fischer-Tropsch liquids
• Fischer-Tropsch synthesis converts solid
hydrocarbons or natural gas into liquids
• Biomass is gasified under high temperature and
pressure to produce CO and H2 (this differs from the
first step in thermo-chemical gasification, discussed
earlier, which is carried out in the near-absence of air)
• The gases are then sent to a reaction chamber,
where catalysts are used to produce chains of various
lengths
• F-T diesel is cleaner-burning than regular diesel
• Overall biomass-to-fuel conversion efficiency of 4652% is expected
Fischer-Tropsch liquids (continued)
• The process is more expensive using biomass than
coal (break-even oil prices of $70-80/barrel and $5055/barrel, respectively, are required)
• It can make use of plant material that has too much
lignin for production of ligno-cellulosic ethanol
• There are still problems related to impurities and
fouling of equipment that need to be solved, and
there is room for better process integration
• Overall, this is a promising method for large-scale
production of biofuels from a wide range of biomass
sources
Solar-driven biomass gasification
• In conventional thermo-chemical gasification or F-T
synthesis, some of the biomass energy is combusted to
produce heat that drives the reactions, and only a portion
of the C atoms end up as part of the product gases or
liquid fuels
• Use of high-temperature heat from solar thermal towers
would allow essentially all of the biomass to be
converted to fuel, reducing the biomass and land
requirements by a factor of 3 (with ethanol yields of ~
42,000 litres per ha of biomass plantation per yr)
• As solar thermal energy can be stored, the production
facility would operate 24 hours per day
• Biomass would be produced in the regions with highest
productivity, then transported by ship or train to semi-arid
regions where concentrating solar thermal energy is
viable
Production of Hydrogen
• Hydrogen is one of several fuels that can be produced
by thermo-chemical gasification of biomass, but is worth
highlighting here because it can also be produced by
electrolysis of water using solar- or wind-generated
electricity
• The overall conversion efficiency from sunlight to
biomass will be very small compared to using solar PV –
the efficiency of photosynthesis (~ 1%) times the
efficiency in conversion from biomass to hydrogen (5060%, or 0.5-0.6)
• Thus, if H2 will be the transportation fuel in the future, it
makes little sense to make it from biomass
• Biomass is interesting as a potential energy source for
fuels (such as ethanol or biodiesel) only if H2 turns out
not to be viable as a transportation fuel, or to the extent
that fuels other than hydrogen are needed (most likely,
there will be applications where H2 is best and
applications where carbon biofuels are best)
Figure 4.25 Biofuel Overview
H yd ro g e n
(H 2)
W a te r g a s sh ift
+ se p a ra tio n
G a sifica tio n
DME
(C H 3O C H 3 )
S yn g a s
C a ta lyse d
syn th e sis
L ig n o ce llu lo sic
b io m a ss
A n a e ro b ic
d ig e stio n
M e th a n o l
(C H 3 O H )
F T D ie se l
(C xH y)
B io g a s
P u rifica tio n
SNG
(C H 4 )
B io o il
H yd ro tre a tin g
a n d re fin in g
B io d ie se l
(C xH y)
S ugar
F e rm e n ta tio n
E th a n o l
(C H 3 C H 2 O H )
E ste rifica tio n
B io d ie se l
(a lkyl e ste rs)
F la sh p yro lysis
H yd ro th e rm a l
liq u e fa ctio n
H yd ro lysis
S u g a r/sta rch
cro p s
O il p la n ts
M illin g a n d
h yd ro lysis
P re ssin g o r
E xtra ctio n
Ve g e ta b le o il
B io o il
(ve g e ta b le o il)
Source: Hamelink and Faaij (2006, Energy Policy 34, 3268–3283, http://www.sciencedirect.com/science/journal/03014215
Current production of
biofuels, trends and yields
Table 4.10 Comparison of biofuel yields (litres per hectare per year)
US
EU
Ethanol from Agricultural Crops
Sugar cane
Sugar beet
5500
Corn
3100
Wheat
2500
Barley
1100
Ethanol from ligno-cellulosic biomass
Corn stover
1100-2200
Miscanthus
7300
Switchgrass
3100-7600
Poplar
3700-6000
Biodiesel from oily plants
Palm oil
Rapeseed
1200
Sunflower seed
1000
Soybean
500
700
Jatropha
Brazil
India
6500-7000
5300
Malaysia
6000
700
From the above
• Biodiesel from palm oil is the only interesting
alternative for biodiesel among those currently
available (although biodiesel from algae might
give many times the yield)
• Ethanol from sugarcane is the best choice, with
ethanol from sugarbeets a close second and
ethanol from ligno-cellulosic crops perhaps
matching yields using sugarcane
• However, production of sugarbeets requires
more energy inputs than production of
sugarcane, while the overall energy balance of
lignocellulosic ethanol will be less favorable than
that of sugarcane ethanol
Figure 4.26a Ethanol production in 2008
France
2%
Other
4%
China
3%
US
51%
Brazil
40%
Ethanol Production in 2008
Total = 67 billion litres
Figure 4.26b Biodiesel production in 2008
Germany
18%
Other
23%
Italy
3%
US
17%
Spain
3%
Thailand
3%
Argentina
10%
France
13%
Brazil
10%
Biodiesel Production in 2008
Total = 12 billion litres
Figure 4.27 World biofuels production, 1975-2008
Production (billions litres/yr)
70
60
50
40
Ethanol
30
20
10
0
1975
Biodiesel
1980
1985
1990
1995
Year
2000
2005
2010
Generation of Electricity
from Biomass
• Co-firing of solid biomass with coal, using steam
turbines
• Biogas in place of diesel in small (5-100 kW)
internal combustion engines
• Integrated gasification/combined cycle (BIGCC)
• Co-firing of biogas with natural gas
• Integrated gasification/fuel cell
• Cogeneration in the sugarcane and palm oil
industries
• Cogeneration in the pulp and paper industry
The conventional way to generate electricity from biomass
is to burn the biomass to generate steam, then use the
steam in a steam turbine. Efficiency is low (typically 2030%)
Advanced techniques (still under development) involve
thermal gasification of the biomass and use of the gases
either in gas/steam turbine combined cycle powerplant or in
fuel cells. Waste heat from the steam turbine or fuel cell
would provide at least part of the heat required for
gasification. Expected overall efficiencies in generating
electricity are in the 40-50% range.
Recap from Book 1 Chapter 3 (Fig. 3.3): Generation of
electricity from a conventional, pulverized-coal powerplant
Generator
steam
High-Pressure Boiler
electricity out
fossil fuel in
Steam
Turbine
air (O 2)
to cooling tower
or cold river water
CO2
water
condensate
and/or
cogeneration
CO2 up the stack
sequestered CO2
out
Condensor
Pump
Source: Hoffert et al (2002, Science 298, 981-987)
cooling water return flow
Recap from Volume 1 Chapter 3 (Fig. 3.6a):
Simple-cycle gas turbine and electric generator
EXHAUST
FUEL
COMBUSTOR
GAS TURBINE
(a)
ELECTRICITY
GENERATOR
COMPRESSOR
TURBINE
INTAKE AIR
Source: Williams (1989, Electricity: Efficient End-Use and New Generation Technologies and Their
Planning Implications, Lund University Press)
Recap from Volume 1 Chapter 3 (Fig. 3.6c):
Combined-cyclepower generation using natural gas
COOLING TOWER
CONDENSER
EXHAUST
ELECTRICITY
STEAM TURBINE
WATER
PUMP
STEAM
FUEL
HEAT RECOVERY
STEAM GENERATOR
(c)
GAS TURBINE
ELECTRICITY
GENERATOR
COMPRESSOR
TURBINE
Source: Williams (1989, Electricity: Efficient End-Use and New Generation Technologies and Their
Planning Implications, Lund University Press)
Table 4.13 Comparison of a typical natural gas and
biogas composition (mole %) and heating value.
CH4
Other HC
CO2
CO
H2 O
H2
N2
LHV (MJ/kg)
Natural Gas
87.6
10.9
1.2
0.3
47.62
Source: Marbe et al (2004, Energy 29, 1117–1137)
Biogas
5.0
12.0
16.0
12.0
11.0
44.0
4.4
Figure 4.28 Flow chart for BIGCC (biomass
integrated gasification combined cycle)
Exhaust
Heat recovery
steam generator
Steam
cycle
Electricity
Make-up
water
Generator
Gas
cooling
Biomass
Boost
compressor
Extraction
air
Pump
Gas
cleaning
Gasifier
Intake
air
Combustor
Gas turbine
Compressor
Electricity
Turbine
Generator
Source: Larson (1993, Annual Review of Energy and Environment 18, 567–630)
Table 4.14 Comparison of electrical and total efficiencies (LHV basis) for
various cogeneration systems using biomass. BICGG=biogas integration
combined cycle.
Technology
Power
(MWe)
Steam
Atm BIGCC
Press BIGCC
Biofuel bioler
2-26
6-77
8-104
Electric Efficiency
Industry
District
Heat
0.17
0.27
0.33
0.38
0.38
0.43
Source: Marbe et al (2004, Energy 29, 1117–1137)
Total efficiency
Industry District
Heat
0.87
1.10
0.71
0.76
0.72
0.90
0.87
0.90
Power:Heat Ratio
Industry
District
Heat
0.24
0.33
0.87
1.00
1.12
0.91
Recap from Volume 1 Chapter 3 (Fig. 3.8): Fuel Cell
Fuel (H2)
Air (Mostly
N2 + O2 )
DC Power
Eelectron flow
Negative ions
OR
Oxidized
Fuel (H2O)
CATHODE
ELECTROLYTE
Fuel
distribution
plate
ANODE
Positive ions
Nitrogen
Sugarcane industry
• Sugar refineries require both heat and electricity,
and have access to substantial amounts of
biomass residue
• Today this residue is used to produce on
average 30 kWh of electricity per tonne, but the
potential is 180-230 kWh/t with biomass
gasification/combined cycle
• The potential is at least 500 kWh/t if residues on
the field, which are currently largely burned off in
Brazil, are also used
Palm oil industry
• Currently produces 25-40 kWh per tonne of
fresh fruit bunch that is processed, using a backpressure steam turbine
• Could produce 75-160 kWh/t with alternative
steam turbines, presumably close to 200 kWh/t
with gasification/combined cycle
Figure 4.29 Electricity from Sugar Cane
Gasifier with STIG
and Steam Conservation
Biomass integrated
gasifierwith combined
cycle (BIGCC)
CEST with Steam
Conservation
Condensing Extraction
Steam Turbine (CEST)
Typical existing factory
0
50
100
150
200
250
kWh of electricity output per ton of cane processed
Source: Modified from Kammen et al (2001, Clean Energy for Development and Economic Growth: Biomass and Other
Renewable Energy Options to Meet Energy Development Needs in Poor Nations, Policy Discussion Paper)
Environmental Issues
•
•
•
•
Soil fertility and productivity
Water use
Use of fertilizers, herbicides, and pesticides
Atmospheric and water pollutant emissions
(biomass production, processing, and end use)
• Genetically-modified organisms
Environmental Issues (continued)
•
•
•
•
•
•
•
Removal of heavy metals from soils
Utilization of ash and separation of heavy metals
Opportunities to treat municipal waste
Impact on erosion
Impact on biodiversity
Indoor air pollution
Employment and rural poverty
Emissions associated with
production and use of ethanol
• Burning of sugarcane fields (still occurs)
• Greater risk of corrosion of tanks with ethanolgasoline mixtures, increased solubility of
petroleum contaminants
• No clear benefit compared to gasoline in terms
of tailpipe emissions
Figure 4.30 Smoke plumes from sugarcane plantations
in Brazil that are burned prior to manual harvesting
Source: Howarth and Bringezu (2009, Biofuels: Environmental Consequences and Interactions with
Changing Land Use), photo by Edmar Mazzi
Emissions and spills associated with
production and use of biodiesel
• Biodiesel is biodegradable and non-toxic, unlike
diesel
• Biodiesel speeds the rate of degradation of
diesel in blends
• Lower tailpipe emissions of CO and
hydrocarbons, with most of the benefit at 50%
biodiesel in biodiesel-diesel blends and a
significant increase in NOx emissions only at
greater than 50% biodiesel
Emissions associated with combustion
for heat and/or power
• Depend on element ratios in the fuel
• Depend on total fuel requirements
• Depend on conversion technologies used
Figure 4.31 Dry matter to coal element ratios
Plant Matter:Coal Concentration Ratio
10
1
0.1
0.01
0.001
B N Na Mg Al P S Cl K Ca Ti V Cr Mn Fe Co Ni Cu Zn As Se Mo Ag Cd Sn SbSmHg Pb
Electric resistance, BIGCC
Electric resistance, NGCC
Pellet boiler
Wood boiler
Oil boiler
Natural gas boiler
Heat pump, BIGCC
Heat pump, NGCC
Primary Energy Used (MJ/MJheat)
Figure 4.32a Primary energy used per unit of delivered
heat in different home heating systems in Sweden
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Total Hydrocarbons (g/MJ heat)
Figure 4.32b Hydrocarbon emissions for different home
heating systems in Sweden
500
400
300
200
100
0
Figure 4.32c SOx emissions from different home heating
systems in Sweden
SOx (g SO2/MJheat)
300
250
200
150
100
50
0
Figure 4.32d NOx emission from different home heating
systems in Sweden
900
800
NOx (g NO2/MJheat)
700
600
500
400
300
200
100
0
BIGCC vs Coal for Electricity
Generation
Table 4.16 Comparison of pollutant emissions (gm/kWh) and CO2 emissions
(gmC/kWh) associated with BIGCC using short-rotation willow fuel, and associated
with coal powerplants.
SO2
NOx
Dust
CO
HC
CO2
Crop
Production
0.024
0.267
0.029
0.267
0.057
5.85
Willow-BIGCC
Crop
PowerTransport
plant
0.001
0.071
0.006
0.214
0.000
0.029
0.006
0.290
0.002
0.55
Total
0.096
0.487
0.057
0.563
0.059
6.40
Source: Faaij et al (1998, Biomass and Bioenergy 14,125–147,
http://www.sciencedirect.com/science/journal/09619534)
Coal Powerplant
Pulverized
IGCC
Coal
0.38
0.2
90.3
0.64
0.05
0.07
222
217
Removal of heavy metals from soil and
separation from flue gas
• Soils in polluted areas tend to have high concentrations
of heavy metals, which are absorbed by the plants
• Heavy metal concentrations are higher in wood chips
and bark than in straw or cereals
• Ash can be separated into 4 different fractions, and most
of the heavy metals end up in a small fraction of the total
ash
• The majority of plant nutrients occur in the ash fractions
that have minimal concentrations of heavy metals, so
these ash fractions can be returned to the soil
Figure 4.33 Distribution of wastewater for the irrigation and
fertilization of a willow plantation in Sweden
Source: P. Aronsson
Figure 4.34 Sewage treatment plant (foreground), aeration
pond (middle ground), and willow plantation at Enkoping,
Sweden
Source: Photograph by P. Aronsson in Dimitriou and Aronsson (2003, Unasylva 56, 221, 47-50)
Impacts on biodiversity
• Positive is short-rotation forestry and grasses
replace agricultural crops
• Negative if large-scale clearing of tropical forests
for soybeans of palm oil, or clearing of the
cerrado for sugarcane or soybeans, occurs
Figure 4.35 The Brazilian cerrado, potential land for soybean and
sugarcane cultivation and home to > 900 species of birds and 300
species of mammals, many threatened with extinction
Source: (C) by Luiz Claudio Marigo/naturepl.com
Global Warming Impact and
Pollutant Emissions of Wood- and
Charcoal-based stoves
Table 4.18 Emissions (gmC per kg of fuel) associated with
different technologies for using biomass for heating, and Cequivalent (in terms of global warming) of non-CO2 emissions (CO,
CH4, and NMHCs)
Figure 4.36a Ratio of ceramic-stove-to-wood-stove or charcoal-basedto-wood-stove CO2 emissions as computed by various researchers
2.0
CO2 Emission Ratio
1.6
1.2
0.8
0.4
0.0
Ballis
Smith
Ballis Brocard Smith
IPCC
Figure 4.36b Ratio of ceramic-stove-to-wood-stove or
charcoal-based-to-wood-stove CO emissions
5.0
CO Emission Ratio
4.0
3.0
2.0
1.0
0.0
Ballis
Smith
Ballis Brocard Smith
IPCC
Figure 4.36c Ratio of ceramic-stove-to-wood-stove or
charcoal-based-to-wood-stove CH4 emissions
6.0
CH4 Emission Ratio
5.0
4.0
3.0
2.0
1.0
0.0
Ballis
Smith
Ballis Brocard Smith
IPCC
Figure 4.36d Ratio of ceramic-stove-to-wood-stove or
charcoal-based-to-wood-stove NMHC emissions
2.5
NMHC Emission Ratio
2.0
1.5
1.0
0.5
0.0
Ballis
Smith
Ballis Brocard Smith
IPCC
Figure 4.36e Ratio of ceramic-stove-to-wood-stove
or charcoal-based-to-wood-stove TSP emissions
6.0
TSP Emission Ratio
5.0
4.0
3.0
2.0
1.0
0.0
Ballis
Smith
Ceramic/Wood
Ballis Brocard Smith
Charcoal/Wood
IPCC
Global warming impact of biomass for
cooking compared to natural gas
• Combustion of solid biomass in various kinds of
stove emits CO and NMHCs (which produce
ozone), and CH4 and N2O (which are GHGs)
• The global warming effect of these emissions
(excluding CO2, which is a valid exclusion if the
biomass is produced sustainably) is several
times that of the CO2 released from the
combustion of natural gas, as seen in the next
figure
Figure 4.37 Efficiency of different cooking fuel/technology
combinations, and ratio of total CO2-equivalent
GHG emissions to that using natural gas
0.8
0.7
16.0
Efficiency
14.0
Ratio to Gas including CO2
12.0
0.5
10.0
0.4
8.0
0.3
6.0
0.2
4.0
0.1
2.0
0
0.0
GWP Ratio
Ratio to Gas excluding CO2
Gas
LPG
Kerosene
Kerosene
Eucal-imet
Eucal-ivm
Eucal-ivc
Eucal-3R
Acacia-tm
Acacia-imet
Acacia-ivm
Acacia-ivc
Acacia-3R
Root-tm
Root-imet
Root-ivm
Must-tm
Must-imet
Must-ivm
Must-ivc
Rice-tm
Rice-ivm
Dung-tm
Dung-ivm
Dung-ivc
Dung-Hara
Efficiency
0.6
Net Energy Yield Producing and
Using Biomass
• Biofuels (ethanol, biodiesel)
• Solid biomass
• Biogas
Net Energy Yield of Biofuels
•
•
•
•
•
•
Ethanol from corn (kernels)
Ethanol from sugarcane
Ethanol from woody biomass
Ethanol from corn stover
Ethanol from sugarcane residue
Biodiesel from vegetable oils
Figure 4.38 Biofuels and coproducts from
corn and soybeans
A g r ic u ltu r a l
p r o d u c ts
B io r e fin e r y
P r o d u c ts
E t hanol
C orn grain
W et m illing
U se
Liquid f uel
C orn oil
C orn glut en m eal
C orn glut en f eed
E dible oil
If a p p lic a b le
A nim al f eed
C orn s t ov er
C orn s t ov er
proc es s
E t hanol
E lec t ric it y
E x port t o pow er grid
S oy bean
m illing
S oy bean m eal
S urf ac t ant
S oy beans
B iodies el
B iodies el
proc es s
S oaps t oc k
G ly c erine
Source: Kim and Dale (2005b, Biomass and Bioenergy 29, 426–439,
http://www.sciencedirect.com/science/journal/09619534)
S olv ent
Energy Inputs to be considered during the
production of biofuel feedstocks
• Energy to make fertilizers, herbicides, and
pesticides
• Energy to produce seeds
• Energy for irrigation
• Energy used by farm machinery (for soil
preparation, seeding, harvesting)
• Energy used to make the farm machinery
• Energy for drying prior to transportation
Energy used during the processing of
feedstocks into biofuels
• Transportation of workers
• Transportation of biomass inputs and of solid
wastes
• Energy used to manufacture the processing
facility
• Energy used by the processing facility
• Energy used to supply and treat water
The key parameter of interest is the Energy Return
Over Energy Invested (EROEI)
This is the ratio of the energy value of the biofuel
and any co-products produced from the biomass,
to the total energy input. It should be substantially
> 1 if producing the biofuel is to be worthwhile
Table 4.19 (upper part) Annual energy inputs used to produce corn or
ligno-cellulosic crops, as estimated in different studies, and EROEI up
to the point where crop leaves the farm.
Results are for a moist corn yield of 8.7 t/ha/yr or a woody crop yield of
13.5 t/ha/yr. Energy required to produce the woody crop is less than
half that required to produce the corn crop, so the EROEI for the woody
crop is much larger
Fertilizer embodied energy (GJ/ha/yr)
Herbicide + Insecticide energy (GJ/ha/yr)
Direct energy use (GJ/ha/yr)
Other energy inputs (GJ/ha/yr)
Total energy to produce corn (GJ/ha/yr)
Crop yield (kg moist crop/ha/yr)
Crop energy yield (GJ/ha/yr)
EROEI so far:
Corn
9.86
1.07
6.26
2.26
18.65
8746
139.8
7.5
Cellulose
2.49
0.14
4.36
0.43
7.38
13450
242.1
32.8
From the above, 19 GJ of energy inputs are required to produce 140
GJ (8.7 t) of corn, giving an EROEI up to this point of about 7.5.
From the lower part of Table 4.19, the 140 GJ of corn energy
corresponds with 77 GJ of glucose (the rest being other materials in the
corn), which in turn are converted into 62.5 GJ (2943 litres) of ethanol.
The energy inputs required to produce the ethanol are
•
•
•
•
19 GJ/2943 litres = 6.34 MJ/litre in the production of the corn
6-12 MJ/litre of coal and/or natural gas at the ethanol plant
2 MJ/litre of electricity primary energy
1.5 MJ/litre of other energy inputs (such as to build the ethanol plant
and for water treatment)
The total energy inputs are thus 16-22 MJ per litre of ethanol produce,
but a litre of ethanol contains only 21 MJ of energy. Thus, the
energy yield ranges from -1MJ/litre to +5 MJ/litre. However, some
products (animal feed) other than ethanol are produced and these
save the energy otherwise used to make these products, so an
energy credit can be given – up to 4 MJ per litre of ethanol
produced.
Figure 4.39 A 450 million litre-per-year corn
ethanol plant in South Dakota
Source: Tollefson (2008, Nature 451, 880–883)
Key points, ethanol from corn:
• The Energy Return over Energy Invested is justly barely
greater than 1.0 (1.5-1.8), and is less than 1.0 for some
studies if energy credits for co-products are excluded
• The energy used in producing the corn is equal to about
one third the energy content of the ethanol that is
produced
• The fossil fuel energy inputs at the ethanol plant are
equal to about half to 2/3 the energy value of the ethanol
• This energy in some plants occurs largely as coal (hardly
a “green” fuel)
• At other plants the energy input is natural gas (which is
hardly in abundance)
• The net energy gain for ethanol-from-corn depends on
energy credits to the meat-production industry (which
fuels over-consumption of meat in the western world,
with its own long list of environmental and other
problems)
Ethanol from sugarcane
From Table 4.22, an average sugarcane yield in Brazil
is ~ 70 t/ha/yr or (in terms of energy value), 430
GJ/ha/yr (about 3 times that of US corn). The energy
input per hectare, however, is less than for corn
(about 13 GJ/ha/yr vs 18 GJ/ha/yr).
Furthermore, because of the high glucose content of
sugarcane, the energy requirements required at the
ethanol plant are much less (about 5 MJ/litre) than for
corn (9-15 MJ/itre). Furthermore, the energy input can
be entirely met by burning the residue (called
bagasse) that can be burned to produce heat and
electricity.
The result is an EROEI that averages about 10 today
Ethanol from sugarcane (continued)
In the future, with advanced electricity production from
bagasse (BIGCC), there will be substantial electricity
production in excess of the requirements of the
ethanol plant, giving an EROEI of ~ 20-40 (depending
on future sugarcane crop yields)
However, the longterm (decades to centuries)
sustainability of current industrial methods of
sugarcane production is not clear, particularly if
bagasse and other residues are used to supply energy
rather than returned to the soil. Even if soil macronutrients (N, P, K) can be replaced with fertilizers,
depletion of micro-nutrients could be a problem in the
long term.
Ethanol from ligno-cellulosic crops
• Projected yields are based on expected gains
based on current R&D
• High EROEIs (~ 6-8) are projected, assuming
that biomass residues can be used to supply the
ethanol plant energy requirements
• However, if the residues need to be returned to
the soil to maintain longterm soil productivity, the
EROEI would be much smaller
Biodiesel from vegetable oils
• The main crops are soybeans and canola (in
North America esp), sunflower (in Europe), and
palm oil (in Indonesia, Malaysia, Thailand)
• Soybeans are already used to produce animal
meal (but also yield vegetable oils), while canola
is a preferred source of vegetable oils (but also
provides some animal meal)
Market chain reaction:
• Production of soybeans to produce oil for biodiesel
increases the supply of animal feed as a byproduct
• This will be offset by a reduction in the pre-existing
soybean production dedicated to production of animal
feed
• But this also reduces the supply of soy oil for non-energy
purposes
• So there will be an increase in canola production
• The adjustments in non-biofuel soybean production and
in canola production will be such (ideally) that there is no
net change in the supply of animal feed or in the supply
of vegetable oil for non-energy purposes
The net result, given the proportions of oil and protein in
soybean and canola, and the substitutability between
soybean feed and canola feed, is that the energy credit per
kg of soybean meal that is produced as a by-product of
biodiesel production, is given by
Ecredit =1.62 Esoybean – 0.73 Ecanola
where Esoybean = energy required to produce and crush
soybeans, and Ecanola = energy required to produce and
crush canola.
As Ecanola > Esoybean, the energy credit for the production of
soybean meal as a co-product of biodiesel can be negative!
The reason Ecanola > Esoybean in turn is because soybean is a
nitrogen-fixing crop and canola is not (so it needs larger N
fertilizer inputs, and N production has a high energy
requirement)
Also note that the negative energy credit from the soybean
meal co-product of biodiesel production depends on the
fact that soybean meal is the marginal protein meal in the
market (that is, increases or decreases in protein meal
demand are met with increases or decreases in the
production of soybean meal) and that canola oil is the
marginal vegetable oil in the market (so changes in the
demand for vegetable oil are met with changes in the
production of canola oil)
Estimated EROEI for biodiesel
from oily crops
• Canola (rapeseed), 1.0-2.0
• Soybeans,1.4 to 2.2
• Jatropha, 4.6-5.3 in India
0.5-2.7 in Thailand without co-product credits
2-12 in Thailand with co-product credits
Note:
• A large part of the EROEI for biodiesel from
soybeans or canola is due to the energy credit
from the co-production of glycerine (11 MJ/litre,
compared to about 33 MJ/litre for biodiesel itself)
• With large-scale production of biodiesel, more
glycerine would be produced than can be used,
so its only energy value would be through its
combustion for use as a fuel (this would be a
small credit)
Impact of the production and use of
biofuels on GHG emissions
• The avoided emissions are the emissions associated
with the production and use of the fuels (gasoline and
diesel) that the biofuels replace
• The direct emissions are the emissions of CO2 from the
fossil fuels used in the production of biofuels (substantial
coal or natural gas in the case of corn ethanol) and
emissions of N2O from the application of N fertilizers
• There are additional indirect emissions due to clearing of
forests or peatland in order to establish palm oil
plantations, or deforestation in the Amazon due to crops
displaced by new sugarcane plantations, or changes in
land use due to induced changes in the prices of
agricultural commodities (in the case of corn ethanol, for
example)
Range of
estimates of the
direct impact
on GHG
emissions of
replacing
gasoline and
diesel with
biofuels (Table
4.27)
Source: Worldwatch Institute
(2006, Biofuels for Transportation:
Global Potential and Implications
for Sustainable Agriculture and
Energy in the 21st Century)
for transportation. Source: WWI (2006, Tables
11-1 to 11.3).
Biofuel
Emission
Number
feedstock
Change
of studies
Conventional ethanol
Corn, E90
+3.3%
1
Corn, E100
-13% to –38%
6
Sugar Beet, E100
-35% to –56%
5
Molasses, E85
-1% to –51%
1
Sugar Cane, E100
-87% to –96%
2
Wheat, E100
-19% to –47%
5
Cellulosic ethanol
Wheat straw
-57%
1
Corn stover
-61%
1
Hay
-68%
1
Grass
-37% to –73%
4
Waste wood
-81%
1
Crop straw
-82%
1
Poplar
-51% to –107%
2
Biodiesel
Rapeseed
-21% to –48%
11
Pure plant oil
-42%
1
Soybeans
-53% to –78%
4
Soybeans
+0% to +100%
1
Tallow
-55%
1
Waste cooking oil
-92%
1
Indirect effect on GHG emissions through induced
changes in land use when land formerly used for food
or pasture is converted to biofuel production
• If corn is devoted to ethanol production, more soybean
feed is needed for animals, so the price of soybeans
goes up, which encourages expansion of soybean
plantations into tropical rainforests
• One assessment with a model of the global agricultural
economy predicts that replacement of gasoline with US
corn-ethanol increases GHG emissions by 100%, rather
than reducing them by 20%!
GHG debt incurred when grassland, tropical forests, or tropical
peatland are converted to biofuels production (Table 4.28)
Original land type
Indonesian and Malaysian
peatland
Indonesian and Malaysian
lowland tropical forest
Brazilian Amazon
Brazilian cerrado
Brazilian cerrado
US central grassland
US abandoned farmland
Crop and
biofuel
Initial debt
(tC/ha)
palm oil
biodiesel
palm oil
biodiesel
soybean
biodiesel
soybean
biodiesel
sugarcane
ethanol
corn ethanol
corn ethanol
941
Portion
of debt
assigned to
biofuels
87%
191
87%
86
201
39%
319
23
39%
37
45
100%
17
37
19
83%
83%
93
48
Source: Fargione et al (2008, Science 319, 1235–1238)
Time required
to pay back
initial debt
(years)
423
EROEI for the use of solid
biomass fuels for heating
Willow
in and
New
Yorkgas
state
(Table
4.29)
Table
11.34 Energy
greenhouse
balance
of a willow
plantation in New York state, US, over a 23-year cycle involving 7
harvestings. Source: Heller et al. (2003).
Energy Balance
Yield
11.93 odt/ha/yr
236.3 GJ/ha/yr
5435 GJ/ha
Input, production with fertilizer
Input, production with biosolids
Input, transport 96 km by truck
EROEI, production only with
fertilizers
EROEI, production with
fertilizers + transport
EROEI, production with
biosolids + transport
Source: Heller et al (2003, Biomass and Bioenergy 25,147–165,
http://www.sciencedirect.com/science/journal/09619534)
19.8 GJ/odt
0.358 GJ/odt
0.226 GJ/odt
0.189 GJ/odt
55.3
36.2
47.8
Woody biomass in Norway (Table 4.31),
excluding any fertilizer inputs
Source: Based on Raymer (2006, Biomass and Bioenergy 30, 605–617,
http://www.sciencedirect.com/science/journal/09619534)
Biomass supply to Europe (Table 4.33)
Biomass
Location
Biomass
Source
Transport
Mode
Scandinavia
Forestry
residues
Forestry
residues
Forestry
residues
Forestry
residues
Shortrotation
willow
coppice
Eucalyptus
plantation
Chips by
ship
Chips by
trains
Pellets by
ship
Pellets by
train
1100 km
Scandinavia
Scandinavia
Scandinavia
E Europe
Latin
America
Distance
Biomass
Energy
loss
Input
GJ/tonnedry delivered
1.6
1.6
EROEI
12.6
1100 km
1.6
4.6
4.3
1100 km
0.5
1.2
16.7
1100 km
0.5
2.5
8.0
Pellets by
ship
2000 km
0.1
1.0
9.4
Pellets by
ship
11500
km
0.4
1.4
14.1
Source: Hamelinck et al (2005, Biomass and Energy 29, 114–134,
http://www.sciencedirect.com/science/journal/09619534)
Switchgrass
pellets
Table 11.40 Energy
terms inin
theCanada
production of(Table 4.35)
switchgrass pellets. Source: Samson et al. (2005).
Activity
Energy (GJ/tonne)
Establishment
0.028
Fertilizer+Application
0.460
Mowing
0.034
Bailing
0.197
Transport
0.072
Biofuel production total
0.791
Pellet mill construction
0.043
Pellet mill operation
0.244
Delivery
0.193
Pellet production total
0.480
Overall total
Energy supplied
EROEI
1.27
18.5
14.6
Source: Samson et al (2005, Critical Reviews in Plant Sciences 24, 461–495)
Table 11.41 Energy terms in the production of 30
oven-dry tonnes
(ODT)/ha/yr
of napier(Table
grass in Brazil.
Napier
grass
in Brazil
4.36)
Terms in brackets are for the case without application
of N fertilizer. Source: Samson et al. (2005).
Activity
Energy (GJ/ha/yr)
Establishment (every 3 yrs)
0.18
N fertilizer
3.69
Other fertilizer
2.29
Lime
4.37
Pesticides
0.02
Mechanical weeding
0.18
Harvest
7.21
Transport (16 km) for processing
1.23
Machinery embodied energy
2.27
Total input:
23.1 (19.4)
Energy yield @ 16.44 GJ/ODT
493.2
EROEI
21.3 (25.4)
Densification (0.1-0.3 GJ/t)
3-9
Drying (2.6-5.2 GJ/t)
78-156
94-188
Total input:
EROEI
2.6-5.2
Source: Samson et al (2005, Critical Reviews in Plant Sciences 24, 461–495)
Figure 4.40 Energy required to produce and delivery various fuels for
heating in Sweden, as a fraction of the energy content of the fuel
0.18
Energy Input (MJ/MJfuel)
0.16
20
Transportation
Production, Harvesting, Processing
EROEI
18
16
0.14
14
0.12
12
0.10
10
0.08
8
0.06
6
0.04
4
0.02
2
0.00
0
Source: Gustavsson and Karlsson
(2002, Energy Policy 30, 553-574,
http://www.sciencedirect.com/
science/journal/03014215)
EROEI
0.20
EROEI for the production of
gaseous biofuels
Figure 4.41 Energy input to make biogas from different
biomass materials in Sweden
50
Energy input/output (%)
40
Transport of raw materials
Transport of digestate
Handling of raw materials
Spreading of digestate
Biogas plant - electricity
Biogas plant - heating
30
20
10
0
Grease Municipal Slaugher Tops &
Pig
sep.
org.
- house leaves of manure
sludge
waste
waste
sugar
beet
Straw
Source: Berglund and Borjesson (2006, Biomass and Bioenergy 30, 254–266,
http://www.sciencedirect.com/science/journal/09619534)
Cow
manure
Ley
crops
Figure 4.42 Efficiencies in producing fuels from biomass
Ethanol
from Corn
Ethanol from
Sugarcane
F2006
W2007C
Based on Bioenergy Input
Only
W2007N
M2004
Based on total energy
input
M2004
M2004
Ethanol from wood
F2006
from
soybeans
P2008
from
rapeseed
P2008
Biodiesel
S2005
S2005
soybeans
Ethanol from corn
& corn stover
KD2005a
KD2005a
KD2005a
KD2005a
Ethanol+electricity
from woody crops
HF2005
HF2005
Methanol now
Methanol future
Fuels from
woody crops
(HF2006 &
TY2008)
Ethanol now
Ethanol future
Hydrogen now
Hydrogen future
FT diesel now
FT diesel future
0.0
0.2
0.4
0.6
Efficiency
0.8
1.0
20
10
P2004
PiP2005
SM2004
F2006
O2005
B2001
O2005
PaP2005
PiP2005
W2001
F2006
C2004
PiP2005
PiP2005
KD2005a
KD2005a
KD2005a
KD2005a
HF2006
HF2007
HF2008
HF2009
Methanol now
Methanol future
Ethanol now
Ethanol future
Hydrogen now
Hydrogen future
FT diesel now
FT diesel future
Percent of Total Energy Input
Figure 4.43 Biofuel inputs and output
100
90
80
70
60
50
40
30
Process Energy Input
Agricultural Energy Input
Bioenergy Input
Total Output Energy
0
Biomaterials
Figure 4.44 Principle routes for the synthesis of organic
chemicals from biomass feedstocks
benzene
lignin
xylene
toluene
phenols
fibers, dyes, solvents
intermediates
adhesives
phenolic resins
polymers
wood
hemicellulose
xylose
furfural
ethylene
ethanol
cellulose
glucose
butadiene
synthetic rubber
polymers
starch
lactic acid
crops
acids
fats & oils
glycerol
soaps, detergents
Source: Geiser (2001, Materials Matter: Towards a Sustainable Materials Policy, MIT Press, Cambridge)
Figure 4.45 Energy requirements to produce PET (from
petroleum) and PLA (from biomass)
90
Primary Energy Use (GJ/tonne)
80
Fossil fuel feedstock
Process energy
70
60
50
40
30
20
10
0
PET
PLA, current
PLA, future
Source: Detzel et al (2006, in Renewables-Based Technology, John Wiley and Sons, Chichester)
Alternative uses of land for
reduction of GHG emissions
• Production of bio-energy crops (discussed
above)
• Biological carbon sequestration
• Simultaneous bioenergy crop production and
biological carbon sequestration
• Bioenergy crops and geological carbon
sequestration
Biological C sequestration
• Buildup of above-ground biomass
• Buildup of normal soil C
• Buildup of biochar
Table 4.41 Estimated rates of accumulation of soil
carbon due to improved land management that can
be sustained over a period of 50 years.
System
Cropland
Biofuel croplands
Grasslands
Forests
Degraded lands
Agroforestry
Total
Global
Land Area
(Mha)
150
13
47
164
109
21
504
Rate of C
Accumulation
(tC/ha/yr)
0.3
0.6-1.2
0.5-0.7
1.0-3.0
0.8-3.0
0.3-0.5
Global Total
(GtC/yr)
0.045
0.008-0.016
0.024-0.033
0.164-0.492
0.087-0.262
0.006-0.011
0.33-0.86
Source: Lemus and Lal (2005, Critical Reviews in Plant Sciences 24, 1–21
Biochar
• Produced through slow pyrolysis (the first step in
thermo-chemical gasification, discussed earlier)
• Pyrolysis drives off volatile materials (which can
be captured and used for energy)
• The remaining solid is highly resistant to
decomposition
• When added to soils, it improves soil fertility,
structure, and water retention
• However, it might accelerate decomposition of
pre-existing soil organic matter
From Box 4.2, the avoided CO2 emissions from
alternative uses of land are
• Improved management within existing land uses:
0.3-3.0 tC/ha/yr
• Reforestation: 2-10 tC/ha/yr
• Dedicated bioenergy crops displacing coal for electricity
generation: 5 tC/ha/yr, plus perhaps another 0.4-2
tC/ha/yr through buildup of soil C with careful
management
• Brazilian sugarcane ethanol displacing gasoline,
7 tC/ha/yr
• H2 + biochar with capture of released CO2: 14 tC/ha/yr
• Dedicated production of H2 from biomass with capture
and geological sequestration of CO2: 5-7 tC/ha/yr
• Avoided deforestation: up to 300 tC/ha/yr
Future biomass potential from
plantations
• Depends on the available land area for
plantations
• Depends on the productivity
(biomass/hectare/year) of the plantation
Assuming no expansion of current agricultural
and pasture land areas, the only land available
for plantations will be surplus agricultural and
pasture land. Whether there is any surplus in
the future, and how much, depends on
• Human population
• Phytomass requirements per person
• Productivity of agricultural land and of
pastureland
Figure 4.46 Trend in grain yield averaged
over various regions
4000
3500
World
All developing
3000
South Asia
Yield (kg/ha/yr)
Sub-Saharan Africa
2500
2000
1500
1000
500
0
1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005
Year
Source: Hazell and Wood (2008, Phil. Trans. Royal Soc. B, 363, pp495–515 )
Large increases in the productivity (food/area)
of
agricultural
lands
are projected
Table
11.50. Projected ratio
of agricultural
yields
2050 compared
to agricultural
1998 according
to in 2050
Table
4.43inProjected
ratio of
yields
a range to
of 1998
scenarios,
in the absence
of of scenarios, in the
compared
according
to a range
increasing
CO2 and climatic
change.
Source:
absence
of increasing
CO2 and
climatic
change.
WWI (2006).
Region
North America
Western Europe
Eastern Europe
Former Soviet Union
Japan
East Asia
South Asia
Oceania
Sub-Saharan Africa
Caribbean and Latin America
World
Yield Ratio
1.6-3.2
0.9-1.9
2.1-4.1
3.2-6.7
2.7-3.0
2.3-3.2
3.7-5.6
2.4-4.6
5.6-7.7
2.8-4.5
2.9-4.6
Source: Worldwatch Institute (2006, Biofuels for Transportation: Global Potential and
Implications for Sustainable Agriculture and Energy in the 21st Century)
Phytomass requirements per person
depend on
• Proportion of meat in the diet, and
• Inverse feed efficiency for production of animal
meat (kg phytomass per kg of meat produced)
Recap of Volume 1 Figure 7.12: Phytomass energy flows in the
world food system.
Source: Wirsenius (2003, Journal of Industrial Ecology 7, 47–80)
From Table 4.45: Amount of phytomass (in terms of its
energy value) needed to produce 1 kg of food product
or 1 kg of protein for human consumption
From Table 4.46: Daily phytomass requirements with presentday world average feed intensities (45 kg phytomass/kg meat, 8
kg phytomass/kg dairy product):
Affluent:
Moderate:
Vegetarian:
Vegan:
140 MJ/day
64 MJ/day
27 MJ/day
20 MJ/day
Current world average: 70 MJ/day
Same as above, but with lower feed intensities (due to more
use of inhumane industrial-scale production systems)
(namely, 30 kg/kg for meat, 5 kg/kg for dairy)
Affluent:
96 MJ/day
Moderate:
47 MJ/day
Vegetarian: 24 MJ/day
Vegan:
20 MJ/day
With current world average diet: 53 MJ/day
From Table 4.47:
Current cropland area is
1452 Mha
Current pastureland area is 3405 Mha
Total land area for food is 4857 Mha
Land available for bioenergy plantations with a human population of 8.8 billion:
Universal vegetarian diet: 3500-4200 Mha (depending on future agricultural yields)
Universal moderate diet:
0-3400 Mha
Universal affluent diet:
0 Mha
The energy that could be supplied (as biomass), assuming biomass yields of 200 GJ/ha/yr
on surplus agricultural land and 100 GJ/ha/yr on surplus pastureland, is:
Universal vegetarian diet: 370-500 EJ/yr
Universal moderate diet:
0-340 EJ/yr
By comparison, total world primary energy demand today is about 500 EJ/yr
(Note: energy yields on Brazilian sugarcane plantations are ~ 400 GJ/ha/yr today and are
projected to reach 800 GJ/ha/yr in the future)
Big increases in the yield of
bioenergy crops are projected
Table 4.49 Current and projected future yields of switchgrass in
different regions of the US, assuming no change in climate
Source: Larson (2006, Energy for Sustainable Development 10, 109–126
Costs
• Cost of solid fuels: typically $2-4/GJ, vs $2-3/GJ
for coal at present
• Costs of liquid fuels from biomass: generally less
than $1/litre
• Capital costs of powerplants using biomass:
$2000-4000/kW, vs $600-900/kW for natural gas
powerplants (but natural gas is likely to be
expensive in the long run) and $1200-1600/kW
for coal powerplants without CO2 capture)
• Cost of electricity from biomass at $2/GJ: 7-13
cents/kWh
Figure 4.47a Present production costs of various liquid fuels
Ethanol from
cellulose
Ethanol from
grain (EU)
Gasoline
(wholesale)
Ethanol from
corn (US)
Ethanol from
sugarcane
(Brazil)
0
0.2
0.4
0.6
0.8
1
Euros per Litre Gasoline Equivalent
Source: Modified from Worldwatch Institute (2006, Biofuels for Transportation Global Potential and
Implications for Sustainable Agriculture and Energy in the 21st Century)
Figure 4.47b Present biodiesel production costs
Diesel fuel
Biodiesel from
rapeseed (EU)
Biodiesel from
soybeans (US)
Biodiesel from
waste grease
(US)
0.0
0.2
0.4
0.6
0.8
1.0
Euros per Litre Diesel Equivalent
Source: Modified from Worldwatch Institute (2006, Biofuels for Transportation Global Potential and
Implications for Sustainable Agriculture and Energy in the 21st Century)
Table 4.53 Costs and efficiency of direct combustion steam turbines for
generating electricity from biomass, and the resulting cost of electricity
assuming 7% financing over 20 years. FB=fluidized bed.
Size
(MW)
3.4
10
15
50
60
Boiler
Tech nology
Pile
Stoker
FB
Stoker
Stoker
Capacity
Factor
0.9
0.9
0.9
0.8
0.8
Efficiency
0.16
0.13
0.13
0.24
0.28
Capita
l Cost
($/kW)
4235
2875
3116
2191
1946
Operation and
Maintenance Costs
Fixed
Variable
($/kW/yr)
(c/kWh)
274
0
270
0
254
0
81
0.95
67
0.75
Cost of Electricity
(cents/kWh)
Fuel at Fuel at
$0/GJ
$2/GJ
8.5
12.9
6.9
12.5
7.0
12.5
5.1
8.1
4.3
6.9
Source: Western Governors’ Association (2006) Clean and Diversified Energy Initiative,
Biomass Task Force Report, www.westgov.org/wga/initiatives/cdeac/Biomass-full.pdf
Heat
Credit
(cents/
kWh)
6.4
8.7
8.7
3.9
3.1
Figure 4.48 Cost of wood-fired powerplants in Finland
Specific investement costs in euros per kW
2000
1500
1000
500
0
0
50
100
150
Installed plant capacity in MW
Source: IEA (2003,
Renewables for Power Generation, Status and Prospects, 2003 Edition, International Energy Agency, Paris)
200
Figure 4.49a Cost of supplying increasing amounts worldwide of
biofuels using Fischer-Tropsch synthesis. A key factor in the cost
estimate is the future cost of rural labour, which depends on the degree of
economic development and hence on the socio-economic scenario assumed
(A1, A2, B1, B2 are from the IPCC SRES report). Gasoline at $1/litre is
equivalent to $18/GJ. Current worldwide oil demand is about 160 EJ/yr.
20
Cost of Biofuel ($/GJ)
A2
B1
B2
A1
15
10
5
0
0
50
100
150
200
250
300
Technical Potential of Biofuels for Transport (EJ/yr)
Source: Hoogwijk et al (2009, Biomass and Bioenergy 33, 26-43, http://www.sciencedirect.com/science/journal/09619534)
Figure 4.49b Cost of supplying increasing amounts
worldwide of electricity from biomass. Current worldwide
electricity demand is ~ 18 PWh/yr
Cost of Electricity (cents/kWh)
10
A2
B2
B1
A1
8
6
4
2
0
0
20
40
60
80
Technical Biomass Electricity Potential (PWh/yr)
Source: Hoogwijk et al (2009, Biomass and Bioenergy 33, 26-43, http://www.sciencedirect.com/science/journal/09619534)