future sustainability of energy crop (denny halim) rev 2
TRANSCRIPT
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CITY COLLEGE OF NEW YORK
DEPARTMENT OF CIVIL ENGINEERING
REPORT
CE G9800
Future Sustainability of Energy Crop
Denny Halim
December, 2012
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City College of New York
Denny Halim
Abstract
Energy crop has been receiving extensive attention due to its potential to replace fossil fuel to replace fossil
fuel. There is an on-going debate about whether energy crop could replace fossil fuel or not, because of
processing of crop to ethanol requires energy input thus there is a possibility of negative net energy balance.
Result from previous study indicated that by considering co-product produced from ethanol processing plant
either from corn or cellulosic plant both could achieve positive net energy balance as much as 60,000 Btu for
cellulosic based ethanol and 20,000 to 30,000 Btu for corn based ethanol. Energy crop requires large area to
produce substantial amount of ethanol. This report estimated that in order to satisfy 20% of energy demands in
2050, energy crop would require 1,735 million ha of land. One of the benefits of energy crop is less emission
of greenhouse gas emission and this study indicated that cellulosic based ethanol could acquire much higher
reduction of greenhouse gas emission compared with corn based ethanol in term of life cycle assessment.
Keywords energy crop, biofuel, corn, cellulose, ethanol, greenhouse gas
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City College of New York
Denny Halim
Table of Contents
Chapter 1. Introduction ...................................................................................................................................... 1
1.1 Overview .............................................................................................................................................. 1
1.2 Objectives............................................................................................................................................. 2
1.3 Method ................................................................................................................................................. 3
1.4 Dissemination Plan............................................................................................................................... 4
Chapter 2. Overview of the Global Crop and Energy Demand ......................................................................... 5
2.1 Crop Land Projection ........................................................................................................................... 6
2.2 Energy Demand Projection .................................................................................................................. 8
Chapter 3. Crop as Energy Source ..................................................................................................................... 9
3.1 Overview of Crop as Energy Source .................................................................................................... 9
3.2 Gross Energy Production from Crop .................................................................................................. 10
3.2.1 Net Energy Production from Crop ................................................................................................. 13
3.3 Projection of Energy Crop for 2030 and 2050 ................................................................................... 16
3.3.1 Energy Production .......................................................................................................................... 16
3.3.2 Greenhouse Gas Emission Reduction ............................................................................................ 17
Chapter 4. Conclusion ..................................................................................................................................... 21
Reference ............................................................................................................................................................ 23
AppendixA: Value-added coproducts from cellulosic ethanol production ...................................................... 26
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Denny Halim
List of Tables and Figures
Table 2-1 The Prospects for Plantation in Developing regions (million hectares) ............................................... 7
Table 3-1 Comparison of Energy Yield for Each Crop Type .............................................................................. 10
Table 3-2 Plant Species for Energy Plantation .................................................................................................... 11
Table 3-3 Ethanol Yield based on Crop Yield ..................................................................................................... 11
Table 3-4 Yield Projection and Yield Comparison .............................................................................................. 12
Table 3-5 Inputs per 1000 L of 99.5% Ethanol Produced From Corn vs Switchgrass ........................................ 13
Table 3-6 Energy use and net energy value per gallon without co-product energy credits ................................. 15
Table 3-7 Energy use and net energy value per gallon with co-product energy credits ...................................... 15
Table 3-8 Calculation of Land Requirement ....................................................................................................... 17
Table 3-9 Carbon Emission Comparison ............................................................................................................ 18
Table 3-10 Potential GHG Reduction ................................................................................................................. 18
Table 3-11 Comparison of GHG Emission Between Gasoline, Corn Ethanol, and Biomass Ethanol ................ 19
Figure 2-1 Global Population Projection .............................................................................................................. 5
Figure 2-2 Past and Future Projection of Arable Land and Land under Permanent Crop .................................... 6
Figure 2-3 Trends in per capita availability of arable land between 1700 and 2050 ............................................ 7
Figure 2-4 Global Energy Demand Based on Several Scenario ........................................................................... 8
Figure 3-1 Biochemical Production of Cellulosic Ethanol ................................................................................. 15
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Chapter 1. Introduction1.1 OverviewSince the middle of 18th Century, people are starting to exploit fossil fuels as main energy source for energy
production. The introduction of fossil fuels caused a tremendous change in the world industry which was
started from the introduction of steam engine to the development of mechanization in industrial society.
Moreover, since the beginning of 19th
century, population growth has been phenomenal. The world population
has experienced huge growth which is from 2.5 billion in year 1950 to approximately 7 billion of population as
of today (U.S. Census Bureau, 2004). The increase of population and development of mechanization in
industrial society are causing the demand for energy to grow accordingly. Based on the data from Key World
Energy Statistics published by International Energy Agency, worlds total final consumption of energy is
4,672 Mtoe in year 1973 to 8,677 Mtoe1
in year 2010. It shows that since almost 30 years ago the energy
demand has almost doubled and as of 2010 still 81.1% of the demand is satisfied from the fossil fuels
exploitation, such as oil, coal, and natural gas, while the rest of the energy demand is supplied by hydro,
nuclear, biofuels, and other sources such as wind, geothermal, and solar. Fossil fuels is non-renewable
resources and need million years to be formed, therefore fossil fuels can be categorized as limited resources.
The demands for energy keep increasing, but on the other hand the energy sources that can be exploited are
very limited. Recently, people are starting to find alternative energy resources to fulfill the increasing demand
and also to reduce the dependency of world with the fossil fuels. Furthermore, the burning of fossil fuels
contributes in the huge amount of carbon dioxide emission and causing the greenhouse effect which resulting
in global warming. Our world has an abundant of renewable energy source, especially from sun and wind, but
unfortunately, technologies to efficiently turning the source to electricity is still very limited and the production
cost to construct an equipment to generate electricity from sun and wind is expensive.
1 Mtoe : Million tonnes of oil equivalent, 1 Mtoe = 41.87 petajoules, therefore 4,672 Mtoe = 195,616 PJ and 8,677 Mtoe =
363,306 PJ
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Ethanol is a renewable energy resource which can be produced from crop or agricultural feedstock. Extensive
research about ethanol as fuels has been conducted in the past and still progressing until now and certainly in
the future. Ethanol has the potential to replace the gasoline and used for motor fuels. Currently, most of the
ethanol is produced from corn with the world production of 22.4 billion gallons and United States is the largest
producer of ethanol with corn as main source with 13.9 billion gallons which is produced from 5 billion gross
bushels of corn (equal with 127 million of tonnes) in 2011 (Renewable Fuel Association, 2012). Brazil is the
second largest producer of ethanol with sugarcane as main source. In 2008, it was reported that 61% (297
million tonnes) of total produced sugarcane (487 million tonnes) in Brazil was used to produce 5.8 billion
gallons of ethanol (StrathKirn Inc., 2009). However, there are still many issues and debates whether ethanol
produced from crop could really be sustainable or not. Because of the ethanol needs crop to be used as raw
material, means that there are some land needs to be dedicated for the ethanol production thus reducing the
potential land could be used for agriculture or producing human food, in other word, there are considerable
amount of land use change. Moreover, the energy balance of the ethanol production, especially from corn is
still debated due to energy input for the ethanol production is almost equal or larger than the energy output
which is the amount of produced ethanol itself.
1.2 ObjectivesThe objectives of this report are to:
a) Discover globally the limit of the crop could be used for energy source, in term of sustainability, landarea availability, GHG reduction and human food consumption
b) Find out sustainable maximum amount and percentage of energy produced from the crop
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1.3 MethodThe research is conducted by researching through secondary data.
The estimation of energy production from the dedicated energy crop will be estimated for the future projection
for year 2030 and 2050. The basis data for the estimation are:
a) Projection of world population;b) Projection of cereal crop production and demand in land area and land use basis;c) Projection of energy production and demand and Greenhouse Gas Emissiond) Net energy output from dedicated energy crop per hectare of land for several major type of energy
crop.
From those data above, sustainability will be defined as the maximum area of land could be used for dedicated
energy crop related with net energy output and reduction of fossil fuels consumptions and greenhouse gas
emission reduction.
The calculation result from energy crop projection will be utilized to analyze the future condition with the
increase of energy crop compared with the condition where there is no increase of energy crop and the energy
source is still majorly from fossil fuels. The main parameter in the analysis would be:
Net Energy Production, Greenhouse Gas Emission Reduction, and Land Area (Land Use Change).
In conducting the calculation, several assumptions would be needed in order to make simplifier calculation.
General assumptions would be as follows:
a) There is an increase of efficiency in producing the energy from dedicated energy crops due toimprovement in production technology in the future.
b) There is an increase of production of dedicated energy crop due to improvement in biotechnology inthe future.
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c) One crop yield will be used to represent global crop yield for easier in calculation by considering thebest maximum yield.
1.4 Dissemination PlanThe result of this project would be in the form of research article. The dissemination activities would be as
follows, firstly the result would be submitted and presented to interested audiences in the City College of New
York, after receiving the feedback from the interested audiences and the project prove to be successful, the
result will be tried to be published on a research journal website or a website that could be accessed freely by
public. The end users of this research article would be policy maker in the government or related agency,
producer of energy crop, non-government organization which concerned about energy, crop demand, and
global warming.
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Chapter 2. Overview of the Global Crop and Energy DemandGlobal population projection from US Census Bureau showed that population will keep growing which is
shown in the figure below.
Source: U.S. Census Bureau, 2002
Figure 2-1 Global Population Projection
It was estimated that in 2030 and 2050, population will increase to 8 billion and 9 billion of population. This
means that there would be 1.3 times increase in 2030 and 1.5 times increase compared with current global
population which is around 7 billion of population.
The increase of population will lead to considerable impact of higher food and energy demand. Currently,
people are still depending on the unrenewable energy sources which are very limited and would gradually
become scarce in the future. It is the same as food production, in order to produce food, wide area of land is
needed to fulfill food demands which details of required land could be seen on the next chapter.
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2.1 Crop Land ProjectionPopulation growth will lead to the change of land use, such as residential, commercial, and industrial
development, therefore the potential to expand crop land would be limited and need to compete with the
development in other aspects. Other important aspect in expanding crop land would be water. Availability of
water supplies could limit the increase of crop land. At present, agriculture accounts for over 70% of water use
globally, but both the absolute amount of water available for agriculture and its share are expected to decline to
40% by 2050 (OECD/FAO, 2012).
Source: OECD/FAO, 2012Figure 2-2 Past and Future Projection of Arable Land and Land under Permanent Crop
Given commodity prices, technology and competing demands, the feasible scope for area expansion is limited.
FAO predicts that from the 2005-07 base period to 2050 only 10% of the global growth in crop production
(21%) in developing countries) is expected to come from land expansion, with the remainder coming from
higher yields and increased cropping intensity. Arable land is projected to expand by 69 Mha (less than 5%)
with an expansion of about 107 Mha in developing countries being offset by a decline of 38 Mha in developed
countries (Figure 2-2). Almost all of the land expansion in developing countries is projected to occur in sub-
Saharan Africa and Latin America (OECD/FAO, 2012).
0
200
400
600
800
1000
1200
1400
1600
1800
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050
Mha
World Developing countries Developed countries
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From figure 2-1 and 2-2 above, availability of arable land per capita for 2012, 2030 and 2050 could be
estimated which are 0.22, 0.19, and 0.18 ha/capita. Forecast about availability of arable land per capita also
could be seen on the Figure 2-3.
Source: (Land Commodities Asset Management AG, 2009)
Figure 2-3 Trends in per capita availability of arable land between 1700 and 2050
As shown on the figure, per capita availability of arable land will keep declining due to exponential population
growth and limited land available for crop. In 2050, it was expected that there would be 18% decline from
2012 of 0.22 to 0.18 ha/capita.
Table 2-1 The Prospects for Plantation in Developing regions (million hectares)
Cropland measures
Present cropland
(1992)
Potential
croplandLatin America 179.2 889.6
Africa 178.8 752.7
Asia (ex. China) 348.3 412.5
Total 706.3 2054.9
Source: (Hislop & Hall, 1996)
Based on the report Biomass Resources for Gasification Power Plant from Hislop & Hall in 1996, there
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would be 2054.9 million ha of potential cropland in developing regions. Based on the projection of arable land
under permanent crop from OECD/FAC , cropland required in developing country in 2025, 2030, and 2050 are
959 million ha, 975 million ha, and 1,036 million ha, respectively which means that there would be excess of
potential cropland in 2050 of 1,018.9 million ha.
2.2 Energy Demand ProjectionIn 2010, global primary energy consumption was 523 EJ (IEA, 2012). This primary energy consumption
mostly satisfied with fossil fuel, such as oil (32.4 %), coal (27.3 %), and natural gas (21.4 %), thus it made up
81.1% of global primary energy consumption. OPEC estimated 2010 global gasoline consumption which was
21 million barrel/day (321.9 billion gal/year) and also projected 2035 global gasoline consumption which
would be 27 million barrel/day (413.9 billion gal/year). It means that in 2035, gasoline will experience 29%
increase of demand.
Note: Top three lines are in primary energy, lower six lines in final energy.
Source: (WWF, 2011)
Figure 2-4 Global Energy Demand Based on Several Scenario
WWF compiled the projection of energy demand from several scenarios. For this paper, scenario from shell
blueprint will be selected and the estimation will consider primary energy demand. It was projected that in
2030 and 2050, primary energy demand will become 650 EJ and 780 EJ.
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Chapter 3. Crop as Energy Source3.1 Overview of Crop as Energy SourceSince around 1980s, human started to search alternative energy sources that could be sustained for a long
period of time or in other words, energy sources that could be renewed in short period of time. Since the start
of ethanol production, corn was already become major choice for production of ethanol and many researches
were done to improve corn to ethanol production. Recently, research in crop as energy field is starting to shift
out to cellulose/biomass base ethanol. Corn based ethanol is defined as first generation ethanol while cellulose
based ethanol is defined as second generation ethanol. The reason for the change to cellulose base ethanol was
due to corn ethanol is not sustainable because of its low energy return on energy invested, moreover
greenhouse gas emissions of corn ethanol are reported to be marginal at best (Rajagopal, Sextion, Roland-
Holst, & Zilberman, 2007). Corn ethanol is, therefore, ineffectual from a climate change perspective and also
unsustainable from an energy efficiency perspective.
U. S. Departments of Energy made a research project to screen and evaluate more than 100 woody species and
35 herbaceous species. From the research, 22 hardwood species identified as high potential for wood energy
feedstock plantations, poplars and cottonwoods (genus Populus) and willow were selected as model for
development. As for herbaceous crops, switchgrass was selected as model (Kszos, et al., 2000). Those species
are can be used to produce cellulose based ethanol.
Cellulose is the most common organic compound on Earth. About 33 percent of all plant matter is cellulose
(e.g., the cellulose content of cotton is 90 percent and that of wood is 50 percent). Cellulose is an organic
compound with the formula (C6H10O5)n, a polysaccharide consisting of a linear chain of several hundred to
over ten thousand linked D-glucose units. Cellulose is the structural component of the primary cell wall of
green plants, many forms of algae, and oomycetes. The higher potential yield of cellulose is due to the fact that
it is an easier path to sugar because of the high glucose content. While first generation ethanol technology
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effectively converts the starch portion of grain to sugar and then the sugar to ethanol, cellulose is a more direct
route and also contains both 5- and 6-carbon sugars (Haigwood & Durante, 2009).
3.2 Gross Energy Production from CropIn 2007, Europe already utilize 50,00060,000 ha (mainly willow, reed canary grass, miscanthus, and poplar)
of land for solid biomass energy crops, and about 2.5 million ha (mostly rape and cereals such as corn) of land
are utilized for transportation biofuels (Jyvaskyla Innovation Oy & MTT Agrifood Research Finland, 2009).
The quantity of dry matter produced by a biomass species per unit area of production, determines the potential
energy production capacity, or yield, of the available land area. Production is measured in dry matter ton
(dmt)/ha and combined with the HHV of the biomass, the energy yield of the cultivated crop can be calculated.
Table 3-1 Comparison of Energy Yield for Each Crop Type
CropCrop Yield
(dmt/ha/year)
HHV (MJ/kg
dry)
Energy yield
(GJ/ha)Reference
Wheat 7 grain/7 straw (14 total) 12.3 123
Mckendry, 2002
Poplar 10-15 17.3 173 - 259
SRC willow 10-15 18.7 187 - 280
Switchgrass 8 17.4 139
Miscanthus 12-30 18.5 222 - 555
Corn grain 6-81)
162)
96 - 128Shapouri, Duffield,
Wang, 2002Corn stover 0.34 - 4.38 17.4 5.9 - 76.2 Essom Co., LTD
Reed Canary Grass
(RCG)4-7 16.2 64.8 - 113.4
Jyvaskyla Innovaation
Oy, 20091)
Corn grain converted from Bu/acre to ton/ha2)
Source: (Patzek, 2005)
As shown on the table above, corn based material has half energy yield potential compared with cellulose
based material, such as switchgrass, miscanthus, poplar, and willow. Overall, cellulose crop have more yield
compared with cereal crop (corn). Currently, there is an intensive research and development to increase
biomass yields using hybrid plants. It was reported that hybrid poplar species could produce yields of 43
dmt/ha/year in US Pacific NW (McKendry, 2001). Following table shows available plant species that
potentially could produce high yield for energy plantation.
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Table 3-2 Plant Species for Energy Plantation
High dmt/ha Moderate dmt/ha
(marginal/degraded land)Woody species Herbaceous
Poplar
Willow
Eucalyptus
Sweet sorghum
Sugar cane
Miscanthus
Switchgrass
Cord grasses
Alder
Black locust
BirchCastanea saturia
Plantanus
Nicotania
Source: (McKendry, 2001)
Table 3-1 above shows energy yield based on higher heating value (HHV) which is the maximum amount of
energy potentially recoverable from a given biomass source. The actual amount of energy recovered will vary
with the conversion technology, as will the form of that energy i.e. combustible gas, oil, steam, etc. As for the
current technologies to convert crop to fuel are still limited and operated with certain efficiency. Ethanol
production based on crop yield could be seen on the following table.
Table 3-3 Ethanol Yield based on Crop Yield
Crop Yield (tons/ha)
conversion
efficiency(liter/tons)
Ethanol yield
(liter/hectare)
Gasoline
equivalent(liter/hectare)
Switchgrass 8 250
1)2000 1340
Corn 6 400
2)2400 1608
Wheat2) 2.8
2)340
2)952 638
Sugar cane
2)
65
2)
70
2)
4550 3049Source: (Pimentel & Patzek, 2005)2)
Source: (Rajagopal, Sextion, Roland-Holst, & Zilberman, 2007)
Switchgrass conversion efficiency was only 250 liter/tons compared with corn and wheat ethanol conversion
efficiency which was 400 liter/tons. Based on Table 3-1, switchgrass potential energy yield was 139 GJ/ha,
therefore if 1 liter of ethanol = 34,353.56 kJ, energy available from switchgrass ethanol conversion = 69 GJ/ha.
This means that the efficiency to convert switchgrass to ethanol from its energy yield potential was only 50 %,
while efficiency of corn energy potential was 85% (energy available from corn ethanol conversion 82 GJ/ha
and corn potential energy yield = 96 GJ/ha). Technology in converting crop to energy still the limiting factor
which is shown that currently only 50% of switchgrass energy potential could be utilized. One of the problem
in processing switchgrass is the method to process cellulosic based material to ethanol, which is requiring
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more steps, such as hydrolysis compared with starch and sugar processing.
Table 3-3 also shows that sugar cane has good potential because of high yield but with low conversion
efficiency which only produced as much as 70 liter/tons. One of the major problems in sugarcane is quick to
decay. Sugargane begins to decay as soon as it is harvested and must be processed within a day or so, leading
to logistical problems for transport and handling with no effective storage (StrathKirn Inc., 2009).
Table 3-4 Yield Projection and Yield Comparison
Unit
Ethanol Yield Projection
2000 2005 2010
Corn ethanol plant yield
Dry milling gal/bu (L/ton) 2.6 (387) 2.7 (402) NA1)
Wet milling gal/bu (L/ton) 2.5 (373) 2.6 (387) NA1)
Cellulosic ethanol plant yield
woody biomass gal/dry ton (L/dry ton) NA1)
76 (288) 98 (371)
Herbaceous biomass gal/dry ton (L/dry ton) NA1)
80 (303) 103 (390))these cases were not evaluated
Source: (Wang, Saricks, & Santini, 1999)
At cellulosic ethanol plants, the unfermentable biomass components, primarily lignin, can be used to generate
steam (needed in ethanol plants) and electricity in cogeneration systems. The estimation of 76 gal/dry ton
ethanol yield in
Table 3-4 was a simulation conducted by National Renewable Energy Laboratory (NREL) for ethanol plants
which was constructed and started to operate in 2005. Such ethanol plants consume 2,719 Btu of diesel fuel
and generate 1.73 kWh of electricity per gallon of ethanol produced. Simulation also was conducted for
cellulosic ethanol which will be operating in 2010, and it was projected to yield 98 gal/dry ton of woody
biomass. The plants will consume 2,719 Btu of diesel fuel and generate 0.56 kWh of electricity per gallon of
ethanol produced (Wang, Saricks, & Santini, 1999). Herbaceous biomass simulation shows slightly higher
yield compared with woody biomass. In 2007, 50,000 to 60,000 ha of land in Europe are covered with such
herbaceous and woody species which are used to produce ethanol. The largest areas are found in the UK
(mainly miscanthus and willow), Sweden (willow, reed canary grass), Finland (reed canary grass), Germany
(miscanthus, poplar) (Jyvaskyla Innovation Oy & MTT Agrifood Research Finland, 2009).
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3.2.1 Net Energy Production from CropIn calculating net energy produced from energy crop, the energy input must be estimated in order to see
whether energy results resulted in negative or positive net energy output. Table 3-5 below shows a research
that had been done by Pimentel & Patzek in 2005, in order to study the net energy production.
Table 3-5 Inputs per 1000 L of 99.5% Ethanol Produced From Corn vs Switchgrass
Source: (Pimentel & Patzek, 2005)
Based on a gallon of ethanol has energy value of 84,100 BTU, thus a liter of ethanol has an energy value of
5,595 kcal. If compared with the energy input both energy crop from corn and switchgrass, both crops
produces negative net energy output. Output/input ratio for corn and switchgrass were 0.85 and 0.75
respectively, or in term of percentage were -18% (1,002 kcal energy loss) and -33% (1,860 kcal energy loss)
from the output energy value. The largest energy input for corn was mostly used to produce corn grain and
steam for fermentation/distillation process in producing ethanol. Switchgrass has low energy input in
producing switchgrass itself which means that growing switchgrass is more environmental friendly compared
with corn grain, but switchgrass requires more energy for steam production and electricity. In Pimentel &
Patzek analysis, they did not include distribution energy to transport the ethanol.
In United States, 13.9 billion gallons of ethanol are being produced per year (Renewable Fuel Association,
2012) which is equivalent to 9.3 billion gallons of gasoline. In 2011, United States consumed about 134 billion
Inputs Quantity kcal x 1000
Corn Grain 2690 kg 2,522
Corn Transport 2690 kg 322
Water 40000 L 90
Stainless steel 3 kg 12
Steel 4 kg 12
Cement 8 kg 8
Steam 2546000 kcal 2,546
Electricity 392 kWh 1,011
95% ethanol to 99.5% 9 kcal/L 9
Sewage effluent 20 kg (BOD) 69
Total 6,597
Input Quantity kcal x 1000
Switchgrass 2500 kg 694
Transport, switchgrass 2500 kg 300
Water 125000 kg 70
Stainless steel 3 kg 45
Steel 4 kg 46
Cement 8 kg 15
Grind switchgrass 2500 kg 100
Sulfuric acid 118 kg 0
Steam production 8.1 tons 4,404
Electricity 330 kWh 1,703
Ethanol converstion to 99 9 kcal/L 9
Sewage effluent 20 kg (BOD) 69
Total 7,455
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gallons (U.S. Energy Information Administration, 2012), thus ethanol only could satisfy 7% of total United
States gasoline consumption. 13.9 billion gallons of ethanol which means that 15.7 million ha of land was
dedicated to grow corn for ethanol.
In the report from Pimentel & Patzek, the calculation of net energy use was purely conducted by estimating
energy input and energy output from ethanol without considering co-product produced from ethanol
production. Another research which was conducted by Wang, Saricks, & Santini in 1999, ethanol production
from cellulosic plant and corn provide net energy balance where corn ethanol still has 20,00025,000 Btu per
gallon (21.126.4 MJ) of net energy and cellulosic ethanol has over 60,000 Btu per gallon (63.3 MJ) of net
energy. Positive net energy balance in corn ethanol is due to yield of co-product in corn ethanol process. There
are two types of corn processing to ethanol with either dry milling or wet milling process. Dry milling produce
co-product: distiller grain (DGS), while wet milling produce co-product: corn gluten meal, corn gluten feed,
and corn oil. The large positive net energy balance for cellulosic ethanol is largely attributable to two factors:
the fact that little fossil energy is used in biomass farming and cellulosic ethanol conversion and, to a lesser
extent, to the assumption that the extra electricity generated in cellulosic ethanol plants will be exported into
the electric grid to displace electric generation in electric power plants (Wang, Saricks, & Santini, 1999).
Wang, Saricks, & Santini assumed that to produce per gallon of ethanol from switchgrass requires 2,719 Btu of
diesel fuel and for growing switchgrass requires 217,230 Btu per dry ton. They also used assumption of 76
gallon of ethanol could be produced for per dry ton of biomass. Therefore, the energy input would only be
around 6,000 Btu per gallon which is very small compared with the assumption used by Pimentel and Patzek.
List of benefits for cellulosic ethanol production could be seen on the AppendixA (Patton, NA).
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Source: (Patton, NA)
Figure 3-1 Biochemical Production of Cellulosic Ethanol
Shapouri and McAloon in 2001, provide a study result of net energy balance by considering with and without
co-product. The result could be seen on the table below.
Table 3-6 Energy use and net energy value per
gallon without co-product energy credits
Table 3-7 Energy use and net energy value per
gallon with co-product energy credits
Source: (Shapouri & McAloon, 2001)
The net energy balance estimate for corn ethanol produced from wet-milling is 27,729 Btu per gallon, the net
energy balance estimate for dry-milling is 33,196 Btu per gallon, and the weighted average is 30,528 Btu per
gallon. The energy ratio is 1.57 and 1.77 for wet- and dry-milling, respectively, and the weighted average
energy ratio is 1.67.
In United States, corn ethanol production produced not only 13.9 billion gallons of ethanol, but also 39 million
metric tons of livestock feed. More specifically, ethanol producers provided 35.7 million metric tons of
distillers grains, 2.9 million tons of corn gluten feed, and 0.6 million tons of corn gluten meal. For perspective,
that is considerably more feed production than the amount of grain used at all cattle feedlots across the country.
Dry Wet
Corn production 18,875 18,551 18,713
Corn transport 2,138 2,101 2,120
Ethanol conversion 47,116 52,349 49,733
Ethanol distribution 1,487 1,487 1,487
Total energy used 69,616 74,488 72,052
Net energy value 6,714 1,842 4,278Energy ratio 1.1 1.02 1.06
Btu per gallon
Weighted
average
Milli ng processProduction
processDry Wet
Corn production 12,457 12,244 12,350
Corn transport 1,411 1,387 1,399
Ethanol conversion 27,799 33,503 30,586
Ethanol distribution 1,467 1,467 1,467
Total energy used 43,134 48,601 45,802
Net energy value 33,196 27,729 30,528Energy ratio 1.77 1.57 1.67
Production
process
Milli ng process Weighted
average
Btu per gallon
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Interestingly, advances in ethanol production technologies are yielding additional co-products as well.
According to RFA analysis, 40% ofthe nations ethanol bio refineries are capturing corn oil during the ethanol
production process and selling that oil into the feed market, as well as biodiesel and other chemical markets.
All told, U.S. ethanol producers supplied an estimated 1.5 billion pounds of corn oil in 2011 (Renewable Fuel
Association, 2012). Importantly, a recent USDA report concluded that one metric ton of distillers grains
displaced 1.2 metric tons of the traditional corn and soybean livestock feed ration. One bushel of corn yields
2.8 gallons of ethanol and 17.5 pounds of livestock feed in a dry mill. Dry mill plants extracting corn oil also
produce about 0.5 pounds of corn oil per bushel, while wet mills produce 1.5 pounds of corn oil per bushel.
Fully one-third of every bushel of corn is returned to livestock feed and other markets (Renewable Fuel
Association, 2012).
3.3 Projection of Energy Crop for 2030 and 20503.3.1 Energy ProductionIn order to see the impact of energy crop on the land use, total land required to satisfy certain amount of energy
demand is required. It will be assumed that 20% of energy demand will be satisfied with energy crop in 2012,
2030, and 2050. Calculation will be used by using data for cellulosic ethanol (switchgrass), yield in 2030 and
2050 will be assumed to increase 20% of current yield and ethanol yield due to projection from
Table 3-4, it will be assumed that ethanol yield would be 400 L/dry ton.
For the first calculation, it will be conducted based on gross energy output without considering net energybalance. Several determined parameter which is needed to make the estimation would be as follows:
a) Target of energy production = 20% of energy demandb) Energy demand in 2012, 2030, and 2050 = 523 EJ, 650 EJ, and 780 EJc) Energy crop ethanol yield = 400 L/dry tond) Crop yield (20% increase) = 8 dry ton/ha (9.6 dry ton/ha)e) 1 L of ethanol = 23,410 kJ
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Based on the available data above we could obtain results as follows:
Table 3-8 Calculation of Land Requirement
2012 2030 2050
20% of energy demand (EJ) 104.6 130 156
Ethanol Required (billion L) 4,468 5,553 6,664Amount of Crop required (billion ton) 11 14 17
Land required to grow crop (million ha) 1,396 1,446 1,735
Based on the chapter 2.1, the excess available land in developing country in 2050 would be only 1,016 million
ha and if it assumed that developed country only be able to use 20% of its arable land (121 million ha) for
energy crop, thus totally 1,137 million ha would be available for energy crop plantation in 2050. As shown on
table 3-8, 598 million ha of land are still needed in order to satisfy 20% of global energy demand. If 1,137
million ha are fully utilized in 2050, it can only satisfy 102 EJ of energy demand, close with 2012 20% energy
demand. With 1,137 million ha of land, it could produce 11 billion ton of crop and 4,366 billion liters of
ethanol and it only could satisfy 13% of energy demand.
If net energy balance is considered, switchgrass has net energy balance of 21,100 kJ per 1 L of ethanol
produced, therefore based on net energy balance; 1,137 million ha of energy crop essentially only could
produce 91.9 EJ or satisfy 11.8% of 2050 energy demand.
3.3.2 Greenhouse Gas Emission ReductionThe consumption of the fossil fuels release significant quantities of pollutants to the atmosphere. Furthermore,
carbon dioxide emissions released from burning these fossil fuels contribute to global warming and are a
serious concern. Another environmental benefit from the use of energy crops versus fossil fuels for energy
production is a decrease in emissions. Unlike fossil fuels, plants grown for energy crops absorb the amount of
carbon dioxide (CO2) released during their combustion/use. Therefore, by using biomass for energy generation
there is no net CO2 generated because the amount emitted in its use has been previously absorbed when the
plant was growing. Substitution of fossil fuel with biomass could help to reduce the CO2 emission. If
approximately 35 million acres were used to grow energy crops and replace the use of coal for electric
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generation, it would eliminate 6% of annual CO2 emissions in the United States. If a mix of 10% willow was
co-fired with 90% coal, NOx and SO2 emissions would be reduced by 10% (Launder, 2002)
Table 3-9 Carbon Emission Comparison
Energy SourceCarbon Emission
(gram/kWh)Carbon Reduction
Poplar 3961 95.54%
Switchgrass 6841 92.29%
Natural Gas 49618 44.10%
Petroleum 80260 9.57%
Coal 88758 -
*Carbon emissions includes production, transportation, and conversion processes
Source: (Launder, 2002)
It was reported that corn based ethanol provide has little marginal value in GHG emission as shown on Table
Table 3-10 which was estimated by using life cycle assessment technique. The study was done by researching
several studies for GHG mitigation potentials of different feedstocks, conversion, process technologies, and
handling of co-product (Carrquiry, Du, & Timilsina, 2010).
Table 3-10 Potential GHG Reduction
Biofuel Emission Reduction (%)
Sugarcane ethanol 65 - 105
Wheat ethanol -5901)
Corn ethanol -2055
Sugarbeet ethanol 3060
Lignocellulose ethanol 451122)
)Negative number mean increases in GHG emissions2)
Include forest residues, energy crops (such as short tree rotations
(e.g., poplar), and (switchgrass), and crop residues (e.g., corn stover)
Source: (Carrquiry, Du, & Timilsina, 2010)
Most studies coincide in that most biofuel pathways reduce emissions of GHG when compared to the
petroleum energy they displace, especially when land use changes are not included in the analysis. The second-
generation biofuels appear to have higher potentials of GHG mitigation as compared to the first-generation
biofuels. The inclusion of land use change (both direct and indirect) may reduce some or all GHG emission
gains, or even result in net emission increases. Note however that the indirect GHG emissions through land use
change would be smaller in the case of second-generation biofuels as compared to that of first-generation
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biofuels. Massive expansion of cropland by cutting down forests could potentially cause significant increase in
greenhouse gases emission.
Table 3-11 Comparison of GHG Emission Between Gasoline, Corn Ethanol, and Biomass Ethanol
Making
Feedstock
Refining
Fuel
VehicleOperation
(Burning
Fuel)
Net Land Use EffectsTotal
GHG
Changein net
GHG vs
Gasoline
Greet Feedstock
Uptake Credit
Land Use
Change
Gasoline 4 15 72 0 92
Corn Ethanol 24 40 71 -62 74 -20%
Corn Ethanol plus land
use change24 40 71 -62 104 177 93%
Biomass ethanol 10 9 71 -62 27 -70%
Biomass ethanol plus
land use change10 9 71 -62 111 138 50%
Source: (Searchinger, et al., 2008)
Searchinger, et al. in their report uses the term "land use change to refer to all of the carbon storage and
ongoing sequestration that is foregone by devoting land to the production of biofuels. Land, of course, already
exists and tends to store and sequester carbon whether devoted to biofuels or not. Using land to produce a
biofuel feedstock foregoes some of that storage and ongoing sequestration, which in effect causes offsetting
emissions in a variety of ways. Their report considers three following factors that could happen when a land is
used for energy crop:
a) A forest or grassland can be directly converted to grow a biofuel such as corn, resulting in the direct lossof the carbon in the standing trees and grasses and a fair chunk of the carbon after plowing up the soils.
Soils store major quantities of carbon in forests and grasslands (Searchinger, et al., 2008).
b) Second, the same land, if not devoted to biofuels, could continue to sequester carbon. For example, ayoung, growing forest will continue to sequester carbon as the forest grows for many years. This ongoing
sequestration is lost if the land is converted to a biofuel for ethanol. (Although land converted to grow the
biofuel, such as corn, will continue to sequester carbon, the typical biofuel analysis already takes account
of that carbon.)
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c) Third, both of these effects can occur indirectly. For example, if corn in the United States is diverted toethanol production, grasslands or forest could be converted anywhere in the world to replace the corn.
Complicating this analysis, these indirect effects can pass through many steps. For example, soybean land
in the U.S. can be planted in corn, and forest or grassland plowed up in Brazil to replace the soybeans.
One of the options in order to reduce the effect of greenhouse gas emission from cutting down forest for
energy crop is by utilization of abandoned agriculture lands. Abandoned agriculture land is an agriculture land
that has been abandoned because of the soil degradation from extensive use and/or relocation of agriculture
land. Previous study estimated that there are 474 to 579 million ha of abandoned agriculture land (Campbell,
Lobell, Genova, & Field, 2008).
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Chapter 4. ConclusionEthanol produced from energy crop might hold a promising future because of its energy value and more
environmentally friendly compared with fossil fuels. From this study, several points in energy crop have been
obtained:
Ethanol from corn and cellulosic ethanol could give negative net energy balance (-18% and -33% forcorn and switchgrass) if the estimation is done by only considering energy input and energy output.
Corn to ethanol processing produces co-product such as DGS for dry milling and corn gluten meal,
corn gluten feed, and corn oil for wet milling. This co-product could overturn net energy balance for
corn which is 20,000 30,000 Btu (21.1 - 31.67 MJ) per gallon of positive net energy balance.
Cellulosic ethanol produce co-product in the form of heat and electricity from co-generation in
cellulosic ethanol processing plant. If this co-product is considered, positive net energy balance of
cellulosic based ethanol could reach 60,000 Btu (63.3 MJ) per gallon.
Required crop area to satisfy 20% of energy demand in 2012, 2030, and 2050 would be 1,396, 1,446,and 1,735 million ha respectively. Those crop areas could achieve crop yield of 11, 14, and 17 billion
dry ton.
Based on the estimation of energy production, energy crop could only satisfy 11.8% of primary energydemand in 2050 by considering the available land constraint of 1,137 million ha. 11.8% is estimated
with net energy balance. For the estimation without net energy balance, energy crop could satisfy 13%
of energy demand in 2050.
Cellulosic based ethanol could help to reduce much more greenhouse gas emission compared withcorn ethanol and if greenhouse gas emission due to land use change is not considered. Corn based
ethanol has a relatively low margin and could lead to increase greenhouse gas emission which is -20%
to 55%. While cellulosic based ethanol could reduce greenhouse gas emission: 45% to 112%.
In term of sustainability point of view, growing energy crop might give beneficial use considering netenergy balance of energy crop with its co-product in ethanol production. Its co-product could be used
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to feed livestock, thus replacing some amounts of crop and grain that is originally used to feed
livestock. Massive expansion of energy crop may increase greenhouse gas emission, especially the
expansion involves cutting down of forests. Abandoned agriculture land could become one of the best
options for growing sustainable energy crop due to no forest are needed to be cut down.
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AppendixA: Value-added coproducts from cellulosic ethanol production
Source: (Patton, NA)
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