Biofuel Contribution To Mitigate Fossil Fuel CO2 Emissions
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Biofuel Contribution To Mitigate Fossil Fuel CO2 Emissions:
Comparing sugar cane ethanol in Brazil with corn ethanol and discussing land use for food production and deforestation
Luiz Pinguelli Rosa,a� Christiano Pires de Campos,b� and Maria Silvia Muylaert de Araujoc�
COPPE/UFRJ, Cidade Universitária Centro de Tecnologia, Bloco G, sala 101 Ilha do Fundão, CP 68501, 21945-970 Rio de Janeiro, Rio de Janeiro, Brazil
�Received 8 October 2008; accepted 30 April 2009; published online 30 June 2009�
This paper compares the use of sugar cane and corn for the production of ethanol, with a focus on global warming and the current international debate about land use competition for food and biofuel production. The indicators used to compare the products are CO2 emissions, energy consumption, sugar cane coproducts, and de- forestation.
The life cycle emission inventory as a methodological tool is taken into account. The sustainability of socioeconomic development and the developing countries’ need to overcome barriers form the background against which the Bra- zilian government energy plans are analyzed. © 2009 American Institute of Physics. �DOI: 10.1063/1.3139803�
The use of biofuel as a substitute for fossil fuel has became a crucial issue today for several reasons, including �a� the increasing price of the oil barrel and the limited oil resources in the world, �b� the increase in fossil fuel consumption in developing countries, particularly in China, as a result of high economic growth, �c� environmental constraints, mainly greenhouse gas �GHG� emissions and climate change, �d� the challenges of sustainable development and the elimination of extreme poverty in developing countries, and �e� the potential impacts of biofuels on crops for food supply, as well as on deforestation.
A literature review was developed to consider the results of recent publications about the role of the biofuel production in the world for programs of GHG emission reductions and sustainable environmental performance. “Depending on the methodology used to account for the local pol- lutant emissions and the global greenhouse gases emissions during the production and consump- tion of both the fossil and biofuels, the results can show huge differences. If it is taken into account a life cycle inventory approach to compare the different fuel sources, these results can present controversies. For example, a comparison study involving the American oil diesel and soybean diesel developed by the National Renewable Energy Laboratory presents CO2 emissions for the biodiesel which are almost 20% of the emissions for the oil diesel: 136 g CO2 / bhp-h for the biodiesel from soybean and 633 g CO2 / bhp-h for the oil diesel.”
According to other authors2 the quite relevant issue of the carbon content and the related GHG emission factors also shows huge differences. It is very important “to determine the size of carbon pools in native habitats and the amount of carbon lost from these pools when converted to crop production.3 The relevant carbon pools differed depending on the native habitat and the biofuel crop.” A study developed by Fargione et al. about land clearing and the biofuel carbon debt says
a�Electronic mail: email@example.com. Tel.: 55-21-25627024. Tel./FAX: 55-21-22701580. b�Electronic mail: firstname.lastname@example.org. Tel.: 55-21-38656188. c�Electronic mail: email@example.com. Tel.: 55-21-22993080.
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that “when not presented in the literature, dry forest biomass was assumed to be 50% carbon, and US grasslands dry biomass was assumed to be 45% carbon.”4 It is important to highlight that these percentages can result in significant errors and need further research.
Another recent study shows that agricultural crops most commonly used at present for biofuel production and climate protection can readily lead to enhanced greenhouse warming. This state- ment relates to N2O. “When the extra N2O emission from biofuel production is calculated in ‘CO2-equivalent’ global warming terms, and compared with the quasicooling effect of ‘saving’ emissions of fossil fuel derived CO2, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn �maize�, depending on N fertilizer uptake efficiency by the plants, can contribute as much or more to global warming by N2O emissions than cooling by fossil fuel savings.”
Oil still ranks first place among the primary sources of energy, representing 35% of total primary energy in the world, followed by coal, with more than 20%, and natural gas, with a slightly lower percentage. Combined, these three fossil fuels were responsible for three quarters of the world’s energy budget.6 Biomass was dominant throughout the 19th century, being surpassed by coal at the transition from the 19th to the 20th century, and then by oil by the mid-1900s.6
Although its share went down over time, until the 1970s, it has remained nearly constant over the past few decades, at about 10%. One of the reasons for this was the increase in liquid biofuels as substitutes for oil, compensating for the decrease in the traditional uses as firewood.
The oil barrel price went up from US$10 in 1999 to US$70 in 2006, reaching over US$100 in 2007 and US$140 in 2008, and then coming down to less than US$100. One factor that explains this behavior is the forecast of limited world oil reserves and production in the near future.7
Although such forecast is uncertain, it does influence policymakers and the market. Other factors that influence the oil economy and related policies include the increase in energy
consumption �EC� in developing countries, especially in China, and the Organisation for Eco- nomic Co-operation and Development �OECD� dependence on oil import. Last but not least, we should also mention environmental pressures related to global warming as a result of present and historical GHG emissions from fossil fuels.8–11
Besides the Asian developing countries, after more than a decade of hard monetarist restric- tions and a very low development rate, several Latin America countries, including Brazil, have had significant economic growth over the past years. Nonetheless, in spite of the recent income im- provement of part of the poor, social inequality persists in many countries. Left-wing or center-left political parties did win governmental elections in several Latin American countries, and the resulting political changes that were implemented implied a more direct role of the government in the energy sector.
The next section discusses the increasing GHG emissions from fossil fuels in the world and shows that, according to the 2007 IPCC Report, CO2 from fossil fuels is the main contributing factor for global warming �Sec. II�. Section III introduces the case of Brazil, considering energy uses and GHG emissions in the country.
Section IV deals with biofuel production in Brazil. Section V discusses sugar cane ethanol in Brazil and compares it with corn ethanol. Section VI deals with land use, competition with food production, and deforestation. Section VII includes the final comments.
- WORLD CO2 EMISSIONS FROM FOSSIL FUELS
According to the IPCC Fourth Assessment Report,12 there was a 70% increase in the world’s GHG emissions during the 1970–2004 period. CO2 emissions increased to 80%; 77% of GHG emissions in 2004 were anthropogenic. The highest contributions for the increase in GHG emis- sions during the period came from the electric energy system �145%�, followed by transportation �120%�, industry �65%�, and change in land uses and deforestation �40%�. The combined per capita emission from the US and Canada was 27 tons of CO2 equivalent, while in Latin America, it was 8 tons and in Africa, 4 tons.
Therefore, we could state that CO2 is responsible for most GHG emissions, while energy
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continues to be the most important source of emissions, including electricity generation, transpor- tation, and industrial activities. Here is the present situation in the world:
�1� Until now, the developed countries have not reduced their emissions in order to reach the goals of the Kyoto Protocol, whose period of commitment started in 2008 and will end in 2012.
�2� Developing countries tend to increase their emission as their economy grows because they follow the developed countries’ consumption patterns.
Figures 1 and 2 illustrate both statements. Figure 1 shows the energy per capita in different countries. The horizontal axis �X� in Fig. 1 shows the gross domestic product �GDP� per capita, while the vertical axis �Y� shows the energy intensity of the economy �energy per GDP� in such a
FIG. 1. Energy per capita �E / population = E / GDP � GDP / population� Data are from 1980, 1985, 1990, 1995, 2000, and 2005. Source: Calculated from Ref. 13.
FIG. 2. CO2 Emissions per capita from energy �CO2 / population = E / population � CO2 / E� Data are from 1980, 1985, 1990, 1995, 2000, and 2005. Source: Calculated from Ref. 13.
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way that the product XY = energy per capita, represented by the hyperbolas at constant values. The points represent the years 1980, 1985, 1990, 1995, 2000, and 2005 for each country �see legend�.
As shown, developed countries have higher GDP per capita and higher energy per capita. The courses followed by them from 1980 to 2005 are quite parallel to the hyperbolas of constant energy per capita, which means that this rate will remain the same along this period. Spain, on the other hand, has shown a significant increase in energy per capita. There was a reduction in the intensity of energy in most developed countries, but the GDP per capita growth was high. The GDP is expressed in current dollars; nevertheless, the growth of GDP per capita over this 25 year period was impressive.
In the developing countries, the situation is quite different: very low GDP per capita �X axis� and very low energy per capita �hyperbolas near XY axis�. Figure 1 shows an increase in energy per capita, but GDP per capita in general remained very low.
Figure 2 shows CO2 emission per capita from EC in different countries. The horizontal axis �X� represents energy per capita, while the vertical axis �Y� depicts the carbon intensity of the energy system in such a way that the product XY = CO2 emission per capita, represented by the hyperbolas at constant values. The points represent the same years and the same countries as Fig. 1.
The developed countries have higher energy per capita and higher CO2 emission per capita from the energy system. Their CO2 emissions per capita from 1980 to 2005 are not as simple as for energy per capita. Developing countries have very low energy per capita �X axis� and very low CO2 emission per capita from energy transformation �hyperbolas closer to XY axis�. There was a trend to increase CO2 per capita.
III. ENERGY USES AND GHG EMISSIONS IN BRAZIL
In developing countries, EC in the higher income classes is often high; however, once the majority of the population is poor, their EC level is very low. Therefore, there is strong inequality in EC and GHG emissions by family within each country, mirroring inequality in income distri- bution. The same inequality existing between developed countries and developing ones is repro- duced within each country between the high income and the low income classes.14 Such is the case of Brazil. As of 2003, an estimated 12 million Brazilians did not have access to electricity, 88% of which are rural residents. In most of the north region of Brazil �in the Amazon�, there is no grid. There are isolated systems burning diesel oil for electricity generation, which in 2006 spent US$2 billion in subsidies. The governmental program Luz para todos �Power for All� is reducing such discrepancies.15
One in every eight Brazilians owns a car.16 According to Table I, the consumption of energy by cars in 2007 in Brazil was 22.49 Mtoe �megatons of oil equivalent� �13.87 Mtoe of gasoline +8.62 Mtoe of ethanol�, while the consumption of diesel oil in transportation for that same year was 28.83 Mtoe,17 from which it is estimated that roughly 10 Mtoe were consumed for public transportation of passengers. Therefore, 12.5% of the Brazilians consume in their cars more than twice the fuel consumed for public transportation, which is used mainly by 87.5% of the popula- tion, i.e., by those families that do not own a car.
The above calculation does not include the electric energy use in public transportation or the use of diesel in private cars because they were considered insignificant in Brazil. Assuming that CO2 emission from ethanol is zero and CO2
TABLE I. EC in transport �Brazil, 2007�. Source: Ref. 17.
Diesel 28.83 Gasoline 13.87 Ethanol 8.62 Othersa 5.58
aIncludes fuel oil, aviation kerosene, natural gas, and electricity.
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emission from gasoline is approximately equal to that from diesel, CO2 emission from every car owner is 9.7 times higher than that of an individual that does not own a car.
The recent discovery of large oil fields in Brazil by Petrobras—the so-called Pre-sal area in off shore deep waters—places the country in a very unique situation, entirely different from the world trend. Brazilian oil reserves may reach �30 – 80� � 109 barrels, as compared to the current 14 � 109 barrels. However, in Brazil, renewable energy is an important component of the energy matrix. In 2006, renewable energy amounted to 42%, while its shares in the rest of the world were about 10% and 5% in the OECD countries �Fig. 3�.
The renewable energy sources used in large scale in Brazil are hydroelectric energy, alcohol �ethanol� from sugar cane, sugar cane bagasse, firewood, and charcoal �Fig. 4�. Lines in Fig. 4 depict the energy fluxes from energy sources to consumption sectors in the boxes located in the middle. Boxes at the top represent fossil energy, including nuclear energy, while renewable sources are at the bottom, some of them used in large scale.
FIG. 3. Renewable and fossil fuel energy. Source: Ref. 17.
FIG. 4. Energy flows from source to consumption: fossil and renewable energy in Brazil.
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Among the primary energy sources in the top section of Fig. 4, oil, natural gas, and coal are responsible for CO2 emissions, but nuclear is not, unless the entire life cycle is taken into account. Another important observation is that, among the renewable energy sources in the bottom, hydro- electric energy emits GHG.
Although hydropower plant emissions are not included in national inventories of GHG emissions, experimental measures carried out in hydropower reservoirs by a COPPE research group found methane and carbon dioxide emissions, although generally at levels far lower than those of thermopower plants.18
There are in Brazil programs for alternative sources and conservation of energy to avoid GHG emissions involving oil and electricity government-owned companies: �1� the programs for con- servation of energy adopted by Eletrobras and Petrobras; �2� a program implemented by Eletrobras to buy electric energy from wind, biomass, and small hydro �3.3 GW� started in 2003; �3� a blend of biodiesel in diesel oil, according to regulations, starting from 2% and increasing to 3%, involv- ing Petrobras and private companies; and �4� incentives for flex-fuel vehicles that use either ethanol or gasoline in any proportion.
- BIOFUELS IN BRAZIL AND AUTOMOTIVE ETHANOL
There are different sources of biofuels, including �1� forest resources �deforestation and forest management�, �2� energy agriculture �forest plantation, sugar cane, corn, vegetable oils�, �3� ag- riculture wastes �sugar cane bagasse, rice waste, and others, animal wastes�, and �4� urban wastes �solid waste and garbage�. Table II indicates the biomass raw materials with the corresponding technologies, products, and uses in Brazil, as well as the fossil fuels that are replaced.
In rural areas, direct combustion of firewood is important for cooking. This kind of firewood use is not equivalent to deforestation because families in rural areas often collect branches of trees, without destroying them.
The use of charcoal in steel industry is important for avoiding GHG emissions. For each ton of steel, about 2 tons of CO2 are emitted from coke and coal. Charcoal use in steel production avoids that emission and allows a capture of 1 ton of CO2 from the atmosphere due to the carbon fixed in forest plantation stock. Therefore, the net balance when replacing coke with charcoal is the subtraction of 3 tons of CO2 from the atmosphere for each ton of steel. This means that if
TABLE II. Uses of bioenergy in Brazil.
Technology Biomass raw material Products Main use Substitution of fossil fuels
Combustion Firewood Heat Cooking LPG Sugar cane, bagasse, and trash Industry Fuel oil
Electric power Natural gas Wastesa
Bioconversion: • Fermentation Sugar cane Ethanol Transport Gasolineb
- Anaerobic digestion Wastes Biogas Potential use Natural gas Chemical and thermal: • Pyrolysis Wood Charcoal Industry Coal and oil • Gasification Biomass Synthesis gas Industry Natural gas
- Esterification Vegetable oil and other materialsc Biodiesel Transport Diesel
- Cracking Vegetable oil Diesel R&D Diesel • Hbiod Vegetable oil Diesel Pilot Diesel Hydrolysis �2nd generation� Biomass Ethanol R&D Gasolineb
aIncludes urban solid wastes, lixivia from the pulp and paper industry, waste from rice, and others. bIt can also be a diesel oil substitute with the use of some additives; in Brazil, gasoline is blended with 25% of ethanol, besides the use of pure ethanol in flex-fuel vehicles. cIncludes animal fat waste, garbage, and microalgae �R&D�. dTechnology of Petrobras for processing vegetable oil in oil refineries.
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one-third of steel would be produced with charcoal, the steel industry in Brazil could have zero net emissions. However, nearly half of the firewood for charcoal used in steel production comes from deforestation and only half comes from forest plantation. This is a problem that has yet to be solved.
Ethanol is the most important biofuel in Brazil. The Brazilian Alcohol Program started in 1975 after the first oil shock, and, in its first phase, consisted of using ethanol as an additive to gasoline. After the second oil shock in 1979, there was a second phase in which, besides its use as an additive to gasoline, ethanol replaced gasoline in cars whose Otto cycle engines were adapted accordingly. The historical factors contributing for the policy of incentives to start the Alcohol Program included the need of reducing the commercial balance deficit, affected by crude oil imports. Besides, the program also created new jobs in the sugar cane agroindustry and reduced air pollution through the elimination of plumb as an additive to gasoline once ethanol allows high compression in the engine.
By 1985, more than 90% of new car sales were of ethanol fueled cars, but in the 1990s there was a shortage of ethanol in the country. A temporary solution was the adoption of a ternary mix composed of ethanol, methanol, and gasoline to supply part of the market.
19,20 The result was the lack of consumer confidence in ethanol and the consequent reduction in new car sales with ethanol fueled engines to 11% in 1990, 2% in 1995, and only 1% in 2000.21 The reasons for the ethanol shortage were the decrease in crude oil price and the lack of continuity in the governmental policy regarding ethanol.
From 2003 on, flex-fuel car production in Brazil ramped up the automotive use of ethanol. The flex-fuel cars were initially produced in the US in the 1980s, but the technology developed by Brazilian automotive industry engineers in the country is innovative.
22 It uses sensors already existing in the car and matches their readings against information stored in an on board computer to adjust the engine to the fuel. The American flex-fuel cars used a special sensor to identify the fuel and adjust the engine accordingly, but it was expensive and unpractical for Brazil, where the car fleet is dominated by small and middle sized compact, low-cost cars.22
Figure 5 depicts ethanol consumption in Brazil. The total ethanol consumption exceeded 15 � 109 l in 1998, progressively decreasing to 10 � 109 l in 2001, then going up again. It reached 17 � 109 l in 2006, and in 2007 ethanol production exceeded 20 � 109 l, of which 3.3 � 109 l were exported.
17 Figure 6 shows the evolution of new car sales. It points out the dominance of ethanol-fueled cars in the mid-1980s, a decrease in the 1990s, and the exponential growth of flex-fuel cars after 2003, encouraged by the high relative price of gasoline due to the raise in the crude oil price internationally, as well as by global warming-related pressures, among other fac- tors.
FIG. 5. Evolution of ethanol consumption in Brazil ��109 l / year�. Source: Ref. 17.
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The cost of ethanol in Brazil went down from US$20/GJ in 1980 to US$6/GJ in 2006, corresponding to US$40/barrel of oil23 following a learning curve. Therefore, while subsidies were necessary to start the program, they are no longer needed.
- LIFE CYCLE CO2 AVOIDED WITH THE USE OF ETHANOL AS A SUBSTITUTE FOR GASOLINE
- Net avoided GHG emissions: Comparing sugar cane ethanol with corn ethanol
A problem regarding ethanol in some OECD countries, as well as in China, is the fact that corn ethanol is used in some countries. From the perspective of global warming and GHG emissions—for instance, CO2 emissions from fossil fuel burning—corn ethanol is less effective than sugar cane ethanol as a substitute for gasoline.
The advantage of biofuels is that, as biomass grows, it captures the CO2 emitted by biofuel combustion in car engines from the atmosphere. However, the production of 1.3 GJ of ethanol from corn uses up 1 GJ of fossil fuel.24 That is, from each energy unit transformed in heat through corn ethanol combustion, 0.77 energy unit is spent for the production of ethanol from corn. The issue is the consumption of fuel oil for ethanol distillation, as shown in Fig. 7. The variables are as follows:
- A, emissions from fossil fuels to make the equipment and for the construction of buildings for corn and ethanol production in a life cycle analysis;
- B, emissions from fossil fuels to produce fertilizers and other materials; • C, emissions from fossil fuels in corn production �includes emissions from diesel oil in
tractors, mechanization equipment, and trucks for transportation� and from the soil; • D, capture of CO2 from the atmosphere as corn grows; • E, emissions from fossil fuels in ethanol distillation; • F, emissions from electricity generation in the grid for ethanol production; • G, emissions from ethanol combustion in cars; and • H, gross avoided emissions from the use of ethanol as gasoline substitute in a life cycle
Figure 7 shows that there is a balance between CO2 capture from the atmosphere in corn plantation �D� and CO2 emissions �G� from ethanol combustion in cars:
FIG. 6. Sales of gasoline, alcohol, and flex-fuel cars in Brazil. Source: Ref. 21.
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balance of CO2 capture by corn: D = G . �1�
However, there are emissions from fossil fuel use in the production of corn and ethanol. Therefore, if H is the CO2 that would be emitted by the use of ethanol as a gasoline substitute:
net avoided CO2 by corn ethanol: N = H − A − B − C − E − F . �2�
On the other hand, sugar cane has enough of biomass surplus to generate heat and electricity in the ethanol production process �
Fig. 8�. For each 1 GJ of fossil fuel consumed in sugar cane and ethanol production, there is an average of 9 GJ of ethanol �it can reach 11 GJ at best�.24 Therefore, for each unit of energy transformed in heat when sugar cane ethanol is burned in car engines, only 0.11 unit of energy from fossil fuel is spent for the production of ethanol. Besides the bagasse, sugar cane has a significant amount of trash
�leaves and top�, which is often burned before harvesting in order to facilitate the job of workers, but trash can be recovered when mechanization is used instead of manpower in the harvesting of sugar cane. The use of mechanization in sugar cane plantations is increasing in the State of São Paulo, but this reduces employment levels.
The variables represented in Fig. 8 are as follows:
- A, emissions from fossil fuel to make the equipment and for the construction of buildings for cane and ethanol production in a life cycle analysis;
- B, emissions from fossil fuel to produce fertilizers and other materials; • C, emissions from fossil fuel in sugar cane production �it includes emissions from diesel oil
in tractors, mechanized harvesting, and trucks for transportation� and from soil �N2O�, as well as CH4 and N2O emissions from burning sugar cane �trash� before harvesting;
- C�, CO2 emissions from burning sugar cane before harvesting; • D, capture of CO2 from the atmosphere while sugar cane grows; • E, emissions from sugar cane bagasse combustion in ethanol production; • F, emissions from bagasse combustion for electricity generation;
FIG. 7. GHG emissions from corn ethanol production and avoided CO2 emissions.
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- G, emissions in ethanol combustion in cars; • H, gross avoided emissions of the use of ethanol as a gasoline substitute in a life cycle
analysis; and • H�, gross avoided emissions of fossil fuel for electric generation in the grid, which is re-
placed by electric energy sold by the distilleries using the surplus of bagasse �and trash� after their self-consumption in ethanol production.
As shown in Fig. 8, CO2 capture while sugar cane grows �D� is equal to the CO2 emitted when ethanol is burned in car engines �G� plus CO2 emission from the burning of sugar cane before harvesting �C�� plus emissions from bagasse combustion in ethanol distillation �E� and in elec- tricity generation �F� for ethanol production:
balance of CO2 capture by sugar cane: D = C� + E + F + G . �3�
However, there are emissions in sugar cane and ethanol production to be subtracted from the gross avoided emission H + H� in such a way that
net avoided CO2 by sugar cane ethanol: N = H + H� − A − B − C . �4�
In the production of ethanol from corn, the unbalanced emission is A + B + C + E + F in Eq. �2�, while for sugar cane ethanol it is A + B + C in Eq. �4�. So, assuming that variables A, B, and C in Eq. �2� are not too different, respectively, from A, B, and C in Eq. �4�, it is clear that net avoided CO2 from sugar cane ethanol is higher than net avoided CO2 from corn ethanol:
N�sugar cane� � N�corn� . �5�
To calculate the net avoided CO2 emissions, we must subtract, from the gross avoided CO2 emissions due to the use of ethanol as fossil fuel substitute, the emissions of CO2 from fossil fuels used in the sugar cane and ethanol production process, as well as other GHG emitted for the production of sugar cane and ethanol.
We must also express the mass of each non-CO2 GHG in terms of equivalent CO2 emissions. For that end, we have used here the global warming power �GWP� for each GHG as provided in the IPCC 1995 Report, incorporated by the UN Climate Convention as a kind of regulation for
FIG. 8. GHG emissions from sugar cane ethanol production and avoided CO2 emissions.
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policymakers and adopted in national inventories and by the Clean Development Mechanism �CDM�. The GWP figures have been evaluated by IPCC reports according to the definition by Lashof and Ahuja.25 This definition provides the relative effect of each GHG in thermal radiation forcing on Earth’s surface using CO2 as a reference: GWP �CO2� = 1. However, it does not repre- sent the relative effect of each GHG in global temperature increase due to anthropogenic GHG.12
Therefore, 1 kg of gas X corresponds to GWP�X , T� kg equivalent of CO2, where T indicates the period of time for which the GWP is calculated �usually, T = 100 years�.
There is in the literature a range of values for emissions in sugar cane production �it is usual to express alternatively the emission in terms of mass of carbon in the molecule; for instance, the mass of C in CO2 is 12 / �12 + 2 � 16� = 12 / 44 of the CO2 mass and the mass of C in CH4 is 12 / �12 + 4 � 1� = 12 / 16 of the CH4 mass� and for avoided CO2 depending on the case and on the methodology used. For instance, different papers consider alternatively the following:
�a� the best situation, a particular case or the average of a set of farmers and distilleries over a period of time;
�b� either only the gross avoided emission H from the use of ethanol as a gasoline substitute or the gross avoided emission H + H�, including the gross avoided emission H� of fossil fuel for electric generation in the grid;
�c� either only the direct EC or the life cycle analysis, including emissions in ethanol production and in gasoline production to calculate H; and
�d� hydrated ethanol, anhydrous ethanol, or a mix of them in the market.
Sometimes it is not clear which of the possible alternatives was chosen, generating confusion in quotations.
- Numerical results from field research data on sugar cane ethanol
A detailed life cycle analysis was presented in a report funded by the Secretary of Environ- ment of the State of São Paulo.26 The report was based on three surveys, the first one covering 26–31 distilleries, the second one 17–22, and the third one including a larger set of 98 distilleries all over the country. Using this report as a reference, it is possible to calculate representative values for emissions from sugar cane and ethanol production in percentages of CO2 equivalent �Table III�.
The GHG emissions in sugar cane and ethanol production and the CO2 that is avoided by ethanol �kg CO2 equivalent / m3 of ethanol� are presented in Table IV. The calculation of the figures in Table IV deserves a detailed technical explanation. The lower heat value of ethanol is compensated by higher compression rate and better efficiency of the engine. In the use of anhy- drous ethanol as a gasoline additive, in a 25% proportion in Brazil �E25�, 1 l of ethanol corre- sponds to 1 l of gasoline. In the case of hydrated ethanol, the proportion is 1.3 l of ethanol �E100�
TABLE III. GHG emissions in sugar cane ethanol production �percentages of CO2 equivalent�. Based on data from Ref. 26.
Source of emission Kind of emission Percentage
From life cycle �A�: equipment, buildings, etc. In sugar cane production 6.6 In ethanol production 9.5
From fertilizers, etc. �B� In sugar cane production 20.6 From burning sugar cane before harvest �C� CH4 19.1
N2O 18.2 From soil �C� N2O 6.9 From fossil fuel consumption �C� CO2 19.1 Adding up �according to Fig. 10� A 16.1
B 20.6 C 63.3
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to 1 l of E25, which means 1 l of ethanol for 0.77 l of E25 or 0.77 � 0.75 = 0.577 l of gasoline. The direct emission factor of gasoline is 0.0693 kg CO2 / MJ.
27 but in life cycle it becomes 0.0817 kg CO2 / MJ.
28 Using the above data, it is possible to calculate the net avoided CO2 in terms of percentage of fossil fuel CO2 emissions:
P = 1 − �A + B + C�/�H + H�� . �6�
The results are presented in Table IV as follows:
Average Best value Percentage of avoided CO2 For anhydrous ethanol 86.5% 88.2% For hydrated ethanol 80.7% 84.1%
Instead of the hypothesis of the use of bagasse as a substitute for fuel oil to calculate H�, the emissions from electric power generation in Brazilian interconnected grid established for the CDM can be applied. More recent data on the average emissions can be obtained from Macedo et al.,3
considering the 2005/2006 harvest. Their case study focused on a set of Brazilian distilleries that process 100 Mton of sugar cane per year. The results are as follows:
�a� For sugar cane and ethanol production, the total GHG emissions using GWP �Ref. 29� are A + B + C = 436 kg CO2 equivalent / m3 of ethanol.
�b� The net CO2 avoided emissions N = H + H� − �A + B + C� = 2323 kg CO2 / m3 of anhydrous ethanol �formula �4��.
�c� Applying formula �6�, the percentage of fossil fuel CO2 emission avoided due to anhydrous ethanol is P = 84.1%.
The results above, although smaller than those of Table IV, confirm that a very high percentage of GHG emission is avoided by the use of sugar cane ethanol as a substitute for gasoline.
We have estimated below the difference between the percentages of avoided CO2 emission by
TABLE IV. Energy gain, GHG emissions, and percentage of CO2 that is avoided by the ethanol industry in Brazil. Based on data extracted from Ref. 26.
Results from 2002/2003 harvest Average Best value scenario
EC �Mcal/ton sugar cane� Sugar cane 48.2 45.8
Ethanol production 11.8 9.5
Total 60.0 55.3
EP �Mcal/ton sugar cane� �ethanol + electric energy from bagasse surplus� 499.4 565.7 Energy gain �EP/EC� 8.3 10.2 GHG emissions �kg CO2 equivalent/ton cane� From fossil fuel consumption 19.2 17.7
Others 15.3 15.3
Total 34.5 33.0
Total GHG emission �kg CO2 equivalent / m3 of ethanol� �A + B + C in Fig. 10� 405.8 358.7 Net avoided CO2 �kg CO2 / m3 of ethanol� from gasoline and fuel oil for electric energy
N = H + H� − �A + B + C� in Fig. 8 For anhydrous ethanol 2600 2700
For hydrated ethanol 1700 1900
033111-12 Rosa et al. J. Renewable Sustainable Energy 1, 033111 �2009�
sugar cane ethanol and by corn ethanol, predicted by inequality �5�. In the hypothesis of burning fossil fuel for EC at the distillery, as in the case of corn ethanol, the percentage P should be calculated by
P = 1 − �A + B + C + E + F�/H . �7�
In Brazil, nearly 1 ton of bagasse is consumed to produce 2 m3 of ethanol,30 which means about 20 900 MJ / m3. Assuming that this value is the self-consumption of energy at the distillery �from bagasse combustion� and that, instead of bagasse, natural gas is burned, whose emission in life cycle is 0.095 kg CO2 equivalent / MJ,
28 E + F = 20 900 � 0.095 = 1985 kg CO2 equivalent, and using formula �7�, for a first approximation, the percentage of GHG emission that is avoided is reduced to P = 12%.
The above calculation simulates the percentage of CO2 that is avoided in case fossil fuel is burned to produce ethanol. This is what occurs for the production of corn ethanol �Fig. 7�. Even though emissions factors A, B, and C in ethanol production are not the same for corn and sugar cane as raw material, this figure makes it clear that the percentage of CO2 that is avoided by corn ethanol is lower than that of sugar cane ethanol. If P is doubled, its value will nonetheless be small �24%�. Actually, the value of P for corn ethanol can be a little bit higher depending on the efficiency of energy transformation in corn ethanol production.
- Potential of energy efficiency and harvest mechanization for avoiding GHG
- Potential to improve the energy gain from ethanol, bagasse, and trash
The energy balance of sugar cane ethanol can be improved by
�a� increasing sugar cane productivity in tons of sugar cane per hectare, �b� increasing the amount of ethanol produced from each ton of sugar cane, �c� using more trash, which means increasing mechanization to reduce sugar cane burning
before harvesting, and �d� improving efficiency in bagasse and trash energy transformation in heat and in mechanical
and electric energies.
The sugar cane productivity went up from 2024 l per hectare in 1975 to 5931 l per hectare in 2005.31 The production in the 1975–2006 period increased from 89 � 106 metric tons to 426 � 106 metric tons.32 The results for recent years are shown in Table V.
55% of sugar cane was used for producing 17.7 Mm3 of ethanol in 2006, that is, 233 Mton with 75.7 l/ton of sugar cane. In 2007/2008, the production is 20.3 Mm3 of ethanol and the forecast for 2008/2009 is 24 Mm3, from which 58% of sugar cane will be for used for ethanol production.33 The best value is 92 l/ton of sugar cane.33 Should a change in the national average in 2006 occur, reaching the best value above, there should be a 21% increase. It is expected that CO2 saving H �formula �6�� through the use of ethanol as a substitute for gasoline could increase in the same proportion.
The energy generated from bagasse and trash �top and leaves� is quite significant. Each ton of sugar cane has 280 kg of bagasse with 50% of humidity and 2130 kcal/kg,30 providing 596 Mcal per ton of sugar cane. Assuming the same average value for trash, the energy of bagasse and trash is more than double that of ethanol energy �Table VI� calculated with 92 l with 0.8 kg/l and heat value of 6500 kcal/kg.30
TABLE V. Sugar cane and ethanol production and productivity. Source: Ref. 33.
Year Processed cane
�Mton� Ethanol �Mm3�
2003 359.3 14.5 74.8 2006 426.0 17.7 75.7
033111-13 Ethanol, climate change, land use… J. Renewable Sustainable Energy 1, 033111 �2009�
In 2006, the bagasse production reached 121.0 Mton: 71.5 Mton �59.1%� for sugar production, 42.0 Mton �34.7%� for ethanol production, and 7.5 Mton �6.2%� for electric power, part of it to the grid.30 Trash is not computed. Therefore, 94% of bagasse is used to make heat and mechanical work for sugar and ethanol production. If there is a reduction of 20% in this percentage through efficiency improvement, the energy of bagasse available for electric power increases by a factor of 0.25 / 0.062 = 4.
Besides, if 50% of trash is used, thermal energy for electric generation will increase by a factor of 0.75 / 0.062 = 12. Nowadays only a small part of electric energy from bagasse is sold to the grid, the avoided GHG emission H� due to electric energy sale to the grid will be multiplied by a factor of more than 12.
If H� goes up, the amount of CO2 avoided will be higher than the amount avoided from the use of ethanol as a gasoline substitute. The percentage P� of avoided CO2 using H as basis, instead of H + H�, in the denominator of Eq. �6�, is given by the following formula:
P� = 1 − �A + B + C − H��/H . �8�
By comparing Eq. �8� with Eq. �7�, it is clear that the additive term E + F �emissions from fossil fuel consumption in corn ethanol� is replaced in the numerator by a subtractive term H� �emission avoided by fossil fuel saving in electric power generation to the grid by sugar cane bagasse surplus�.
It is clear that, if H� � A + B + C in Eq. �8�, P� � 1. The electric installed capacity using bagasse in 2006 was 2.6 GW,30 85% �2.2 GW� of which were for self-consumption and 15% �only 0.4 GW� were sold to the grid. In that same year, 8357 GW h were produced from sugar cane bagasse, from which 1256 GW h to the grid.30 In the hypothesis of increasing the electric power generation from bagasse by a factor of 4, as pointed above, the installed capacity could become 10.4 GW and 10.4 − 2.2 = 8.2 GW could be sold to the grid, 20 times the current value of 0.4 GW.
So, the electric energy from bagasse to the grid in 2006 could grow by a factor of 20, becoming 25 120 GW h. Assuming that natural gas will be replaced, with a life cycle emission of 0.095 kg CO2/MJ �Ref. 28� and 40% of efficiency, the avoided CO2 calculation gives 2.13 � 109 kg of CO2. Once for that year the production of ethanol was 17.7 Mm
3, the avoided CO2 could be 1200 kg CO2 / m3 of ethanol. The bagasse computed for electric generation in the es- timate above did come from ethanol and sugar production because this industry is integrated. Considering that 55% of sugar cane is used for ethanol production, H� = 660 kg CO2 / m3 of ethanol. Using this figure in formula �8�, as well as the average values in Table IV, the result is P� = 1.10, that is, 110%. Therefore, as well as balancing the full emissions of sugar cane and ethanol production, for each ton of CO2 avoided through the use of ethanol as a substitute for gasoline, more 100 kg of CO2 could be avoided due to the use of bagasse surplus for electric power.
In 2007, bagasse used for electric power was 8.1 Mton,17 and the installed capacity was 2.8 GW. However, direct sale of electric energy from bagasse in 2007 was about 25% of the installed capacity,34 that is, 0.7 GW. In 2008, a bid for electric power in the grid added 2.2 GW of installed capacity using bagasse, and operations should start in the coming years.15 The power predicted by the bid, added to that realized in 2007, totals 2.9 GW, 35% of the potential of 8.2 GW, calculated with the above assumptions and without major technological changes.
TABLE VI. Energy from 1 Mton of sugar cane considering heat values. Source: Ref. 24.
Mcal/ton of cane
92 l of ethanol �best value� 478 280 kg of bagasse with 50% of humidity 596 280 kg of trash with 50% of humidity 596
033111-14 Rosa et al. J. Renewable Sustainable Energy 1, 033111 �2009�
- Scenario for energy per ton of sugar cane and avoided GHG by mechanization
Focusing only on ethanol production and referring to Table V and to Ref. 21, bagasse con- sumption for heat and mechanical work in ethanol production amounts to 42 � 2130 / �426 � 0.55� = 382 Mcal / ton of sugar cane. Subtracting this value from 596 Mcal �Table V�, 214 Mcal of bagasse per ton of sugar cane in ethanol production can be used for electric energy. By the same token, 68.2 Mcal of bagasse per ton of sugar cane were used for electric power generation in 2006.
Considering the use of 1 l of ethanol �average of hydrated and anhydrous� instead of 0.79 l of gasoline, with heat value of 10 400 kcal/kg and density of 0.74 kg/l, the correspondent energy is 0.79 � 0.74 � 10 400 = 6080 kcal per liter of ethanol or 75.7 � 6080 = 460 000 kcal / ton of sugar cane. In the case of 92 l/ton of sugar cane, the equivalent energy will be 559 Mcal /ton of sugar cane.
However, trash recovering is limited because trash is also used to protect and fertilize the soil and because mechanization to avoid cane burning cannot be used in more than 50% of the area with the available technology due to declivity. On the other hand, the burning of bagasse and trash could be done with improved thermodynamic efficiency. Based on such considerations, we were able to build a future scenario, presented in Table VII, as compared to 2006.
The scenario of Table VII does not take into account potential improvements of efficiency in energy transformation that could increase bagasse surplus, for instance, by changing low- efficiency steam systems for electric power. In many cases, low pressure steam is used.
It is reasonable to get more mechanical and electric energy per ton of sugar cane with higher efficiency by decreasing bagasse self-consumption. As a rule, 22 bars of steam pressure are used, which can be increased to 60 or 80 bars, improving efficiency by a factor of 2. The self- consumption of bagasse in ethanol production in some cases is 90% for heat in distillation of ethanol, 5% for mechanical work, and 5% for electric power. If efficiency is improved in the conversion of heat in mechanical and electric energy, the surplus of bagasse will be higher and there will be more electric power to the grid per ton of bagasse. Therefore, H� could be higher again.
The mechanization of harvesting, used in such a way to avoid the burning of sugar cane will allow not only a higher value for H� due to the use of trash in electric power generation but also a lower value of emission C in Eq. �6� or Eq. �8�. However, because of the slopes on part of the lands used for sugar cane plantations, it is impossible to reach 100% of mechanization. If mecha- nization is increased by 50% in relation to the case study presented in Table III, there could be a reduction of 0.5 � 37.3% = 18.6% in CO2 equivalent emission of CH4 and N2O from the burning of sugar cane.
On the other hand, the use of 50% more harvesting equipment will increase emissions from diesel oil in the same proportion. Assuming that half of fossil fuel consumption in Table III is diesel oil, the correspondent emission that represents 0.5 � .19.1% = 9.5% will increase by 0.5 � 9.5 = 4.75%. The net result should be an emission reduction of 18.6 − 4.75 = 13.85%. Diesel oil
TABLE VII. Energy from 1 Mton of sugar cane.
Mcal per ton of cane
Brazil 2006 Future scenario Variation
Ethanol �energy of gasoline replaced� 460a 559b 21% Bagasse for electric energy �partly to grid� 68 214c 314% Trash for electric energy �entirely to grid� 298d Infinite Total 528 1071 102%
aConsidering 75.7 l of ethanol per ton of sugar cane �Brazilian average in 2006�. bWith the best value of 92 l of ethanol per ton of sugar cane. cSelf-consumption of 377 Mcal /ton of sugar cane subtracted. d50% of total mass.
033111-15 Ethanol, climate change, land use… J. Renewable Sustainable Energy 1, 033111 �2009�
can be eliminated by fueling diesel engines with either biodiesel or ethanol with additive. The variation of indirect energy in life cycle of harvesting equipment �variable A in Table III� is not considered in this approximation.
The problem of increasing the mechanization of harvesting is the resulting reduction in work- ers in sugar cane plantations. In 2005, there were 414 000 workers in sugar cane agriculture, 439 000 in sugar production, and 128 000 in the ethanol industry.35 However, manual harvesting of sugar cane is a very hard job that may cause diseases by physical stress. Besides, the burning of sugar cane causes air pollution, which, in turn, is a factor for respiratory conditions for the local population.
- DISCUSSION ABOUT LAND USE, ETHANOL COMPETITION WITH FOOD, AND DEFORESTATION
- Land uses and deforestation
The issue of food crop displacement due to biofuel competition was raised recently by Far- gione et al.4 The paper shows that land use for biofuel increases GHG in atmosphere due to emissions from land use change in the US. The authors used a model for estimating the planted area due to biofuel production.
This problem is not new in Brazil. The displacement of food crops by sugar cane in São Paulo was pointed out a long time ago by Homem de Mello.36,37 In fact, there is indeed displacement of food crops, but its dimensions are very different in the case of sugar cane in Brazil and in corn in the US �Table VIII�. The US share in world corn production is higher than the share of Brazil in global sugar cane production, while the area used for corn production in the US is five times the area for sugar cane production in Brazil.
The area used for sugar cane production in Brazil is 7 � 106 ha—about 45% for sugar and 55% for ethanol—which means that about 4 � 106 ha are used to produce ethanol. For comparison purposes, soy bean uses 21 � 106 ha and cattle pastures occupy 177 � 106 ha. According to data from the Brazilian Institute of Geography and Statistics,16 the country has 152 Mha useful for agricultural purposes. Therefore, sugar cane for ethanol production uses only 2.6% of the area useful for agriculture, without taking into account the recovery of pasture lands that are being degraded.
According to this same source, only 62 Mha are used for food crops, biofuels, and other crops. Therefore, there are 90 Mha available for the expansion of agriculture without deforestation.
The Brazilian area of native vegetation is 440 Mha; most of it is located in the Amazonian rain forest, in the north region of the country. The production of sugar cane is concentrated in the southeast, mainly in São Paulo, followed by the middle west region, with some contributions from the south and northeast regions, but only 0.3% from the north region, where the Amazon is located �see Table IX�. The present impact of sugar cane for ethanol on deforestation is low, as compared to soybean for the external and internal markets, which includes biodiesel production.
Two points should be noted about biofuels and deforestation:
TABLE VIII. Corn in the US � Sugar cane in Brazil. Source: Refs. 16, 32, and 38.
US corn Brazil sugar cane
Percentage of world production �%� 54 33 Area occupied �Mha� 35 7
TABLE IX. Ethanol production in Brazil per region. Source: Ref. 39.
Southeast: 72% Northeast: 7% Middle West: 13% North: 0.3%
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�a� The presence of sugar cane in the middle west region �13%� impacts the savanna in the Brazilian Cerrado, although this kind of vegetation is less dense than rain forest.
�b� The situation of soybean, mainly for exportation but used also for biodiesel, is different because its presence in the north region is high, although biodiesel production in Brazil is relatively small in comparison with ethanol production.
One of the goals of the Biodiesel Program was the use of castor oil, palm oil, sunflower, and other raw materials produced by small farmers. However, the present situation is the dominance of large soybean plantations supplying vegetable oil for biodiesel.
The drivers of deforestation are 4, mainly in the rain forest:
�a� wood extraction, �b� cattle pasture, �c� soybean plantations, and �d� mineral resources exploration.
There are different ways of calculating deforested areas depending on whether or not reforested areas are considered because they were deforested areas at some point. In some studies, the deforested areas considered are only the ones that really changed land use definitely, as in the case of agriculture or pasture. In other studies, the accidental burning of biomass is considered defor- estation. Another issue that can result in different figures is the vegetal classification used in the calculation of carbon emissions, as biomass density can be quite different.
- Potential sugar cane expansion and the external market
The next issue concerning possible impacts of the potential expansion of sugar cane produc- tion is related to ethanol exports as a substitute for gasoline in OECD countries.
The European car fleet features a growing proportion of diesel engines, although there is a non-negligible consump- tion of gasoline either with or without ethanol as additive. Part of the car fleet of Sweden uses a blend of 80% ethanol and 20% gasoline �E80�.
Table X shows the countries with more significant ethanol production as well as the countries to which Brazil exports. Only the US and Brazil use ethanol as gasoline substitute in a large scale.
In 2006, the US ranked first place in ethanol production, followed by Brazil. However, the percentage of ethanol blended to gasoline is very low in the US because gasoline consumption is very high, which makes the US the largest importer of ethanol from Brazil. Therefore, the most important potential market for Brazilian ethanol is the American market, where Otto cycle engines are predominant in the car fleet.
There are other potential importers, such as Japan, where Petro- bras created a joint venture with Mitsubishi to export ethanol. China also uses corn to produce ethanol for cars. In 2006, there were 310 ethanol distilleries in Brazil, and 77 new plants were planned, with investments of over US$14 billions.32 Foreign investors are being attracted to ethanol agrobusiness in Brazil.
TABLE X. Ethanol in 2006. Source: Ref. 40.
Production Volume of Brazilian exports
USA 18 378 � 106 l EUA 1749 � 106 l Brazil 17 000 Netherlands 344 China 3 850 Japan 228 India 1 900 Sweden 201 France 950 El Salvador 183 Germany 765 Jamaica 133 Russia 647 Venezuela 103 Canada 579 Spain 462 South Africa 386 Total 3 417 � 106 l
033111-17 Ethanol, climate change, land use… J. Renewable Sustainable Energy 1, 033111 �2009�
Presently, the North American market is not open to Brazilian ethanol. However, in spite of the weak result of international trade negotiations at multilateral level to open it, there are some reasons to believe that the present situation in the US will change, including
�a� the inefficacy of corn ethanol to mitigate global warming �see Sec. V above�, �b� the higher competition of corn ethanol with food agriculture �see this section�, �c� the lower productivity per hectare and higher cost of corn ethanol �see Table XI�, and �d� the prediction of increasing the percentage of ethanol to 20% of car fuel �see scenario
Based on that, it is reasonable to develop a scenario for future ethanol demand to be supplied through international trade. The gasoline consumption in the US is about 10 � 106 barrels / day. Considering the hypothesis in �d�, with 20% of ethanol and 1.3 l of ethanol for 1 l of gasoline, the future demand will reach 140 � 109 l of ethanol/year, seven times the current Brazilian ethanol production.
The necessary land area, with the same technology and average productivity, should be mul- tiplied by 7, resulting in 28 Mha for sugar cane, 30.4% of the land available for the expansion of agriculture in Brazil.
This percentage is not small if we consider the need of land for food production and other crops, including biofuels, for the internal market and for export to other countries besides the US. If this demand is doubled, in order to supply European countries and Japan, the area needed for sugar cane would reach 56 Mha, which is too large indeed. Besides, there are the problems of a very large monoculture. Second generation technology for ethanol production must change the present prospects.
VII. FINAL COMMENTS
The conclusion is that there is no major obstacle, from the land use point of view, to expand ethanol production for the internal market. However, Brazil should not supply the entire potential market for ethanol in the world if ethanol use becomes a way for global warming mitigation in a large scale.
A more realistic projection indicates a production of about 36 � 109 l of ethanol in 2012, from which 7 � 109 l are to be exported.32 Another scenario predicts 60 � 109 l of ethanol in 2020 with 12 � 109 l for export.42 Brazil can supply such quantities as long as the areas needed are compat- ible with the available lands for agriculture.
As was previously pointed out, CO2 is dominant among GHG emissions and the automotive fleet contributes with 20% of world CO2 emission. The automotive fleet amounted to 890 � 10
light vehicles in 2005 and consumes half of the petroleum products in the world.43 Besides, the fleet increases by 20% per year in China and 3.5% in Brazil, where 5.5 � 106 ethanol powered by vehicles were produced since 1979, and 4 � 106 flex-fuel vehicles produced since 2003 are run- ning either on gasoline or on ethanol. Besides, ethanol is added to gasoline in the proportion of 25%. Therefore, cars use from 25% to 100% of ethanol in Brazil. CO2 emission avoided is substantial.
However, ethanol itself is not enough to mitigate CO2 emissions at world level.
It is also necessary, deep changes, in energy technology, transport �including public transport�, and con- sumption patterns that are still dependent on diesel engines. But ethanol can become an important fuel for different technologies, besides the Otto cycle engines in cars. Combined to additives,
TABLE XI. A comparison of sugar cane ethanol with corn ethanol. Source: Refs. 21 and 41.
Productivity �l/ha� Costs
Sugar cane ethanol 4000–7000 0.19 US$/l �São Paulo� 0.23 US$/l �Northeast Brazil�
Corn ethanol 3500–4700 0.33 US$/l
033111-18 Rosa et al. J. Renewable Sustainable Energy 1, 033111 �2009�
ethanol could power diesel engines used in buses, trucks, and railway locomotives. It can be used as fuel for hybrid vehicles of electrical propulsion—in which the Otto or diesel engine is coupled to an electric power generator that supplies current for an electrical motor and for accumulating energy in batteries—or in fuel cell vehicles to replace combustion engine to supply current for an electrical motor.
Sugar cane is the best way to produce bioethanol from both the economical and the environ- mental point of view, including GHG mitigation through the use of ethanol as a gasoline substi- tute. However, ethanol industry in Brazil must be improved, including the adoption of technologi- cal changes, some of them concerning efficiency in energy transformation and natural resources use. The main changes must be made at the first level:
�a� Improving efficiency in the transformation of chemical energy of sugar cane bagasse in heat for distillation and in mechanical and electric energy for self-consumption and to sell energy to the grid; today, the share of bagasse in electric generation in Brazil is too small and must be increased.
�b� Using the sugar cane trash, which is burned before harvesting to facilitate the manual job of workers; the amount of energy that could be obtained for electric generation is significant.
�c� Item �b� implies the increase in harvesting mechanization in sugar cane agriculture, decreas- ing the number of workers, but work conditions in manual harvesting are harsh.
�d� Improving conditions of workers in sugar cane plantations in some cases, including both the social and the environmental dimension in clean energy production �EP�.
�e� Improving technology both in agriculture and in the industry.
At the second level:
�a� gasification of sugar cane bagasse and trash,
�b� second generation ethanol production through hydrolysis, and �c� biorefineries with multiple by-products or integrated oil and biorefineries in a more advanced
Gasification could either allow high-efficiency conversion into electric energy through com- bined cycle or could be used to produce liquid fuel from gas. Second generation ethanol is hydrolysis acidic or enzymatic, followed by fermentation, that leads to the conversion of biomass fiber �lignin and cellulose� into ethanol.
The commercial use of hydrolysis can reduce sugar cane comparative advantage as compared to other kinds of vegetable used to produce ethanol. On the other hand, the entire mass of sugar cane could be used to obtain ethanol, including the hydrolysis of bagasse and trash, as well as allows the fermentation of pentose to produce ethanol. Macedo32 predicted a time horizon between 2010 and 2020 for second generation ethanol to become commercial, while for gasification this time is a little bit longer, 2015–2025, in spite of the already existing technological uses of wood gasification. In the case of hydrolysis, there are prototypes, and some recent small scale industrial plants are being built around the world for ethanol production, although not yet commercial.
Biorefineries can produce ethanol together with other chemical by-products. For instance, biodiesel production needs ethanol or methanol and uses glycerol as a by-product that can be used to produce gasoline. Since the beginning, ethanol production in Brazil was integrated to sugar production in the so-called annex distilleries. A more advanced concept is the integration of biorefineries with oil refineries, as, for instance, does the H-bio technology developed by Petrobras �Table II� parallel to biodiesel from vegetable oil. Although this is out of the scope of this paper, biodiesel production must be improved in many aspects that are not dealt with here.
Finally, biofuels for private cars must not drop the issue of technical and social efficiencies in transportation nor the encouragement to improve public transportation. A Climate Change policy must find realistic solutions for sustainable development with social justice. The elimination of poverty requires more power per capita in developing countries; however, at the same time,
033111-19 Ethanol, climate change, land use… J. Renewable Sustainable Energy 1, 033111 �2009�
intensive energy use is necessary and the consumption patterns of the high income and middle classes must be changed. It is not possible to deeply mitigate global warming without making changes in business as usual EC.
LIST OF ABBREVIATIONS AND ACRONYMS CDM Clean Development Mechanism CO2 Carbon dioxide CO2 equivalent Carbon dioxide equivalent COPPE Instituto Alberto Luiz Coimbra de Pós-Graduação e Pesquisa de Engenharia
of Federal University of Rio de Janeiro E25 Ethanol 25% GHG greenhouse gas GJ Gigajoules �109� GW Gigawatts �109� GW h Gigawatts hour �109� GWP Global warming potential IPCC International Panel on Climate Change kcal kilocalories �103� kg kilogram m3 cubic meters Mcal Megacalories �106� Mha Megahectare �106� MJ Megajoules �106� Mm3 Mega-cubic-meters �106� Mton Megatons �106� Mtoe Megatons of oil equivalent OECD Organisation for Economic Co-operation and Development
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2 M. S. Muylaert de Araujo, C. Silva, and C. P. Campos, Renewable Sustainable Energy Rev. 13, 696 �2009�. 3 I. C. Macedo, J. E. Seabra, and J. E. A. R. Silva, Biomass Bioenergy 32, 582 �2008�. 4 J. Fargione, J. Hill, D. Tilman, S. Polasky, and P. Hawthorne, Science 319, 1235 �2008�. 5 P. J. Crutzen, A. R. Mosier, K. A. Smith, and W. Winiwarter, Atmos. Chem. Phys. 8, 389 �2008�. 6 IFP Innovation, Energy, Environment �IFP� Report, 2005. 7 C. Campbell, The Coming Oil Crisis �Oxford, New York, 2001�. 8 L. P. Rosa and S. K. Ribeiro, Clim. Change 48, 289 �2001�. 9 L. P. Rosa, S. K. Ribeiro, M. S. Muylaert, and C. P. Campos, Energy Policy 32, 1499 �2004�.
10 L. P. Rosa, C. P. de Campos, and M. S. Muylaert, Sci. Total Environ. 346, 149 �2005�. 11 M. S. Muylaert de Araujo, L. P. Rosa, and C. P. de Campos, Renewable Sustainable Energy Rev. 11, 988 �2007�. 12 “Fourth assessment report,” Intergovernmental Panel on Climate Change �IPPC�, 2007. 13 “Key global indicators,” United Nations Statistics Division report �available at http://data.un.org/Data.aspx?d�CDB&f
�srID%3a29918, updated 22 May 2008�. 14 M. S. Muylaert, C. Cohen, L. P. Rosa, and A. S. Pereira, Clim. Res. 28, 89 �2004�. 15 Energy Planning Enterprise �EPE�, Brazilian Ministry of Energy report 2008. 16 “National statistics,” Brazilian Institute of Geography and Statistics �IBGE� report, 2007. 17 Balanço Energético Nacional �BEN�, EPE, Brazilian Ministry of Energy preliminary results, 2008. 18 L. P. Rosa, M. A. Santos, B. Matvienko, E. O. Santos, and E. Sikar, Clim. Change 66, 9 �2004�. 19 L. P. Rosa and S. K. Ribeiro, Energy Policy 26, 103 �1998�. 20 L. P. Rosa and S. K. Ribeiro, AMBIO 27, 465 �1998�. 21 M. A. F. Dias de Moraes, “Reflections on Brazil’s ethanol industry,” MRE report, 2007, p. 158. 22 H. Joseph, Jr., “Flexible fuel engine techonology,” MRE report, 2007. 23 J. Goldemberg et al., Biomass and Bioenergy �Elsevier, New York, 2004�, Vol. 26. 24 O. A. Braunbeck, I. Macedo, and L. A. B. Cortez, Increasing the available biomass from sugarcane for energy conversion
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033111-21 Ethanol, climate change, land use… J. Renewable Sustainable Energy 1, 033111 �2009�
QUALITY OF RESPONSE NO RESPONSE POOR / UNSATISFACTORY SATISFACTORY GOOD EXCELLENT Content (worth a maximum of 50% of the total points) Zero points: Student failed to submit the final paper. 20 points out of 50: The essay illustrates poor understanding of the relevant material by failing to address or incorrectly addressing the relevant content; failing to identify or inaccurately explaining/defining key concepts/ideas; ignoring or incorrectly explaining key points/claims and the reasoning behind them; and/or incorrectly or inappropriately using terminology; and elements of the response are lacking. 30 points out of 50: The essay illustrates a rudimentary understanding of the relevant material by mentioning but not full explaining the relevant content; identifying some of the key concepts/ideas though failing to fully or accurately explain many of them; using terminology, though sometimes inaccurately or inappropriately; and/or incorporating some key claims/points but failing to explain the reasoning behind them or doing so inaccurately. Elements of the required response may also be lacking. 40 points out of 50: The essay illustrates solid understanding of the relevant material by correctly addressing most of the relevant content; identifying and explaining most of the key concepts/ideas; using correct terminology; explaining the reasoning behind most of the key points/claims; and/or where necessary or useful, substantiating some points with accurate examples. The answer is complete. 50 points: The essay illustrates exemplary understanding of the relevant material by thoroughly and correctly addressing the relevant content; identifying and explaining all of the key concepts/ideas; using correct terminology explaining the reasoning behind key points/claims and substantiating, as necessary/useful, points with several accurate and illuminating examples. No aspects of the required answer are missing. Use of Sources (worth a maximum of 20% of the total points). Zero points: Student failed to include citations and/or references. Or the student failed to submit a final paper. 5 out 20 points: Sources are seldom cited to support statements and/or format of citations are not recognizable as APA 6th Edition format. There are major errors in the formation of the references and citations. And/or there is a major reliance on highly questionable. The Student fails to provide an adequate synthesis of research collected for the paper. 10 out 20 points: References to scholarly sources are occasionally given; many statements seem unsubstantiated. Frequent errors in APA 6th Edition format, leaving the reader confused about the source of the information. There are significant errors of the formation in the references and citations. And/or there is a significant use of highly questionable sources. 15 out 20 points: Credible Scholarly sources are used effectively support claims and are, for the most part, clear and fairly represented. APA 6th Edition is used with only a few minor errors. There are minor errors in reference and/or citations. And/or there is some use of questionable sources. 20 points: Credible scholarly sources are used to give compelling evidence to support claims and are clearly and fairly represented. APA 6th Edition format is used accurately and consistently. The student uses above the maximum required references in the development of the assignment. Grammar (worth maximum of 20% of total points) Zero points: Student failed to submit the final paper. 5 points out of 20: The paper does not communicate ideas/points clearly due to inappropriate use of terminology and vague language; thoughts and sentences are disjointed or incomprehensible; organization lacking; and/or numerous grammatical, spelling/punctuation errors 10 points out 20: The paper is often unclear and difficult to follow due to some inappropriate terminology and/or vague language; ideas may be fragmented, wandering and/or repetitive; poor organization; and/or some grammatical, spelling, punctuation errors 15 points out of 20: The paper is mostly clear as a result of appropriate use of terminology and minimal vagueness; no tangents and no repetition; fairly good organization; almost perfect grammar, spelling, punctuation, and word usage. 20 points: The paper is clear, concise, and a pleasure to read as a result of appropriate and precise use of terminology; total coherence of thoughts and presentation and logical organization; and the essay is error free. Structure of the Paper (worth 10% of total points) Zero points: Student failed to submit the final paper. 3 points out of 10: Student needs to develop better formatting skills. The paper omits significant structural elements required for and APA 6th edition paper. Formatting of the paper has major flaws. The paper does not conform to APA 6th edition requirements whatsoever. 5 points out of 10: Appearance of final paper demonstrates the student’s limited ability to format the paper. There are significant errors in formatting and/or the total omission of major components of an APA 6th edition paper. They can include the omission of the cover page, abstract, and page numbers. Additionally the page has major formatting issues with spacing or paragraph formation. Font size might not conform to size requirements. The student also significantly writes too large or too short of and paper 7 points out of 10: Research paper presents an above-average use of formatting skills. The paper has slight errors within the paper. This can include small errors or omissions with the cover page, abstract, page number, and headers. There could be also slight formatting issues with the document spacing or the font Additionally the paper might slightly exceed or undershoot the specific number of required written pages for the assignment. 10 points: Student provides a high-caliber, formatted paper. This includes an APA 6th edition cover page, abstract, page number, headers and is double spaced in 12’ Times Roman Font. Additionally, the paper conforms to the specific number of required written pages and neither goes over or under the specified length of the paper.
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