|No 59 Em Português|
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Sugarcane: The Best Alternative for Converting Solar and Fossil Energy into Ethanol (*)
C. ANDREOLI1, S. P. DE SOUZA2
1Researcher, Embrapa Soja, C.P 231, Londrina, PR. Email: email@example.com
2Graduating student of Environmental Engineering, UFPR, Curitiba, PR. Email: firstname.lastname@example.org
ABSTRACT: - Brazil and the United States are the world leaders in ethanol production using sugarcane and corn as feedstock, respectively. The objective of this article was to compare some sugarcane and corn parameters, mainly the energy balance regarding their conversion into ethanol, as well as to show a future bio-fuel plant for the Brazilian industry. In order to calculate the sugarcane energy balance data from ORPLANA, UNICA and from the Pitangueiras Plants in São Paulo were used whilst for corn, it were used data from Pimentel and Patzek (2005) and Hill et al (2006). Energy balance concerning corn conversion into ethanol is negative (1.29:1), that is for each kcal of energy supplied by ethanol 29% more energy is used to produce alcohol whilst the sugarcane balance is positive (1:3.24), that is for each kcal consumed in ethanol production there is a gain of 3.24 kcal. Furthermore, sugarcane produces three times more alcohol per area than corn. Sugarcane uses four times less energy than corn, 1.6 billion kcal for sugarcane as compared with 6.6 billion for corn. Production cost of ethanol is U$0,28/L for sugarcane and U$0,45/L for corn. Reduction of greenhouse effect gases (GEG) in the production and combustion of ethanol from sugarcane was 66% compared with 12% for ethanol from corn. The American alcohol industry is viable only because there is a U$4.1 billion subsidies for ethanol production.
(*) Study presented at the Conference of AgriEnergy International Conference, 11 - 13 December, 2006, Londrina, PR, Brazil.
Plants use solar light through photosynthesis to fix atmospheric CO2 in a vast production of biomass. However, a small proportion of this fixed carbon is also used for producing fuel, fibers and lumber. Sugarcane (Saccharum officinarum L., Poaceae famíly), a highly efficient C4 plant, can store about 1% of the radiation incident on biomass per year. Due to two factors – increase of CO2 emission, depletion of petroleum reserves and consequently their price increase – it has been observed lately a progress in the R&D programs to improve the production of biomass and energy as well as the feedstock for the chemical industry as part of a sustainable economy.
Brazil and the United States are world leaders in ethanol production, using sugarcane and corn as feedstock, respectively. Brazil has a share of 50% in the exports of ethanol, mainly to India, Japan and the United States.
Considering the American laws to ban the MTBE (metyl-tert-butyl eter) additive in gasoline mixtures (1999) and the Renewable Fuel Standard (RFS) law signed by President Bush in 2005, alcohol production, that was 5.0 billion liters in 1999, attained 16 billion in 2005. By the RFS, the United States should produce 7.5 billion gallons (28 billion liters) in 2008. It is estimated that, if the European countries, the Unites States and Japan would adopt a mixture of 10% ethanol in gasoline it would be necessary more 60 billion liters of alcohol in 2007.
The objective of this study was to compare several sugarcane and corn parameters, mainly the energy and environmental balance to convert sugarcane and corn into ethanol as well as to show a future bio-fuel plant for the Brazilian industry
Material and Methods
Production, productivity and industrial yield data of sugarcane were obtained from UNICA and ORPLANA (2005) and those of corn from USDA, SHAPOURI et al. (2002) and SHAPOURI et al. (2006). In order to calculate the sugarcane energy balance, data regarding ethanol production were those from the Pitangueiras Region Plants and for corn, data from PIMENTEL and PATZEK (2005) were used. For the estimation of GHG savings in the production and combustion of each bio-fuel instead of fossil fuel, it was calculated the GHG savings relative to the life cycle of fossil fuels (i. e. the energy gain in bio-fuel production) and then it was added to it the net emission in the farm (HILL et al. 2006).
Results and Discussion
In Table 1 are shown some comparative parameters regarding ethanol production from corn in the United States and from sugarcane in Brazil. In spite of the incentive to the production of ethanol from corn in the USA, supported by political power, some class associations and including the USDA, scientists from the Cornell and Berkeley Universities have demonstrated that both from the energy and environmental points of view ethanol-corn production is not sustainable, draining U$4.1 billion paid in subsidies for corn production.
The energy balance for converting corn into ethanol is negative (1.29:1), i. e. for each 1kcal of energy supplied by ethanol more 29% of fossil fuel is used to produce alcohol (PIMENTEL and PATZEK, 2005). The sugarcane energy balance is positive (1:3.24); for each 1 kcal of consumed energy for ethanol production there is a gain of 3.24 kcal by the produced ethanol and furthermore three times more alcohol is produced per area using sugarcane than using corn. This means that if 100% of the United States corn was to be used for ethanol production, this would satisfy only 6% of the needs of petroleum substitution. However, HILL et al. (2006) report that the bio-fuel produced from corn and soybean are viable from the economic, energy and environmental points of view. The energy gain was 1:1.25 for corn and 1:1.93 for soybean; reduction of greenhouse effect gases emission was 12% for production and combustion of ethanol and 41% for biodiesel and this justifies the future production scheme of bio-fuels in Brazil (Figure 1).
Figure 1:. Illustrative scheme of a future energy matrix of bio-fuel Brazil. Sugarcane bagasse would be a heat source for the ethanol-corn and for bio-diesel. Ethanol is used in the transesterification in the production of biodiesel and the CO2 liberated in the ethanol production can be recycled in the production of vegetables or in soft drink and/or sparkling water factories. The biodiesel produced will be used in the transport of sugarcane (field-plant).
Another important aspect is the total fossil energy used in the industry to convert sugars in the same quantity of ethanol. Sugarcane uses four times less energy than corn, 1.6 billion kcal for sugarcane as compared with 6.6 billion for corn (Table 1). It should be emphasized that sugarcane alcohol production costs are much more lower than those of corn alcohol (Table 1), without considering the subsidies paid to the American corn growers and distillers. The production cost of sugarcane ethanol is much lower than that of corn: U$0,28/L versus U$0,45/L. Relative to fossil fuels, emissions of greenhouse effect gases was reduced 66% with the production and combustion of sugarcane ethanol and 12% with the production and combustion of corn ethanol (Figure 2).
Table 1. Comparison between corn ethanol production in the USA and sugarcane ethanol in Brazil.
§ 50% of sugarcane production is for alcohol production in Brazil and 20% of the corn in the USA.
a New units: 89 in Brazil and 40in the USA.
# The sugarcane ethanol energy balance is positive and that of corn is negative
Figure 2. Emission of greenhouse effect gas (GHG equivalent to g CO2/MJ) during production and combustion of bio-fuels compared with gasoline and diesel (corn and soybean, data from Hill et al. 2006).
In order to be viable alternatives, bio-fuels should have a high net energy gain, have ecological benefits, be economically competitive and have large-scale production without hindering food provision. Therefore, it can be concluded from all parameters analyzed in Table 1 that sugarcane is by far the best alternative for ethanol production. Besides the chemistry-ethanol energy, sugarcane diversifies the energy matrix by producing electric energy and heat through bagasse, reducing environmental pollution and permitting the use of straw and tips.
The future scenario shows that only the energy consuming countries, USA, Japan and Europe will need to import more than 10 billion liters of ethanol until 2011/12. If one ton of sugarcane produces 88 liters of ethanol, it would be necessary to add more than 110 million t of sugarcane in order to satisfy the future market which would add 1.2 million hectares more. UNICA forecasts a production growth from 6% to 7% annually attaining a production of 560 million t of sugarcane in 2010/11.
Figure 1 shows a bio-fuel production plant of the future, connecting sugarcane ethanol production with corn ethanol production, between harvests, and with biodiesel from vegetal oils. The surplus of bagasse would be used as heat source. In the conversion of sugars to ethanol 33% of CO2 is emitted and it would be directly recycled in the production of vegetables of high aggregated value. The biodiesel produced would be used in the plant itself for transporting sugarcane and its products at costs much lower than that of diesel.
Sugarcane is by far the best alternative from the economical, energy and environmental point of view, for bio-fuel production.
HILL, J.; NELSON, E.; TILMAN, D. Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels. PNAS, v. 103, p. 11206-11210, 2006.
PIMENTEL, D.; PATZEK, P. Ethanol production using corn, switchgrass, and wood; Biodiesel production using soybean and sunflower. Natural Resources Research. v. 14, n. 1, p. 65-76, 2005.
SHAPOURI, H.; DUFFIELD, J.A.; WANG, M. The energy balance of corn ethanol: an update: USDA, Office of Energy and New Uses, Agricultural Economics. Report No. 813, 14 p. 14, 2002,
SHAPOURI, H. , SALASSI, M., FAIRBANKS, J.N. The economic feasibility of ethanol production from sugar in the United States. Report of the USDA, p. 62. July 2006.
Graphic Edition/Edição Gráfica:
Thursday, 05 May 2011.