Brazilian Biofuels Programmes from the WEL Nexus Perspective

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Brazil’s biofuel programmes viewed from the WEL-nexus perspectiveFigure 4.8 presents a comparison between energy balances of the production of ethanol fromdifferent raw materials, reaffirming the advantage of using sugar cane to produce ethanol.Figure 4.8 Energy balances of the production of ethanol from different feedstocksSource: Coelho et al., 2006.There seems to be a consensus among researchers that ethanol has a very positive directinfluence on mitigating GHG emissions (Goldenberg and Guardabassi, 2009; Hira andOliveira, 2009; Macedo et al., 2008; Pacca and Moreira, 2009; Abdullah et al., 2009). Themitigation occurs through using ethanol as a substitute for gasoline in the transportationsector, as well as through the generation of electricity using sugar cane bagasse that replacesfossil-fuel power generation. Bagasse is burned to produce steam and electric/mechanicalenergy to fuel the process (co-generation process). There is significant potential to generatesurplus electricity. After meeting the steam and electricity needs of the process, up to 80 kWhof electricity per ton of cane can be sold to the grid if existing low-pressure boilers (22 bar,which yield 20 kWh/t of cane) are replaced by high-pressure ones (up to 80 bar). Outputs of120 kWh/t can be reached with better technology and recovery of by-products. Gasificationtechnology under development is expected to reach 300 kWh/t of cane.The exact figures for GHG emissions mitigation vary depending on the assumptions used tocalculate them (e.g. % of ethanol in gasoline, final consumer use of ethanol in FFV vehicles,technologies applied, among others).According to Macedo et al. (2008), for anhydrous ethanol production the total GHG emissionwas 436 kg CO 2 eq/m 3 ethanol for 2005/2006, decreasing to 345 kg CO 2 eq/m 3 in the 2020scenario. Avoided emissions depend on the final use: for E100 use in Brazil they were (in2005/2006) 2181 kg CO 2 eq /m 3 ethanol, and for E25 they were 2323 kg CO 2 eq /m 3 ethanol(anhydrous). Both values would increase about 26% for the conditions assumed for 2020, duemostly to the large increase in sales of electricity surpluses. For these calculations the ‘seedto-factory-gate’approach was adopted, which encompasses the sugar cane production andprocessing through to fuel ethanol at the mill gate (ibid.).Although the use of ethanol as a fuel in Brazil was not the result of a long-term concern for theenvironment, it is widely accepted and documented that the overall positive environmentalaspects of Proalcool far outweigh its potential damage (Rosillo-Calle and Cortez, 1997). Fromthe LCA results found by Luo et al. (2009) it can be concluded that in terms of abioticdepletion, GHG emissions, ozone-layer depletion and photochemical oxidation, ethanol fuelsare better than gasoline. On the other hand, gasoline is a better fuel in terms of humantoxicity, eco-toxicity, acidification and eutrophication (ibid.)36
Brazil’s biofuel programmes viewed from the WEL-nexus perspectiveWhile the energy balance of ethanol has been widely studied, there appears to be no reliablecomprehensive study using the same methodology to address the energy balance for bio-dieselusing different feedstocks. There are more than 100 native plants species identified withpotential of the production of bio-diesel, but the present study focuses on the energy balanceusing LCA of bio-diesel from soybeans, which was developed by Gazzoni et al. (2006) andrecently updated by Rathmann et al. (2010). This choice is based on the fact that soybeansrepresented 84% of the raw material for the production of bio-diesel in Brazil in 2010 (ANP,2011b).Rathmann et al. (2010) show that the total amount of fossil energy needed to produce 810 kgof soy-based bio-diesel is 18,197 MJ. Hence, the final energy balance is positive for soy at74,192 MJ ha -1 . This means that in growing soybeans, for each unit of fossil energy that entersthe system, 5.1 units of energy are produced (ibid.). The data used in this study are presentedin Table 4.7.Table 4.7 Inputs and outputs in producing bio-diesel from soybeans in BrazilEnergy inputs and outputs for growing soybeansFactor Quantity MJLabour 6.3 hours 1,056Machinery 20 kg 1,508Fuel 66 litre 2,765Phosphorous 20 kg 348Potash 20 kg 264Lime 2,000 kg 2,355Boron 1 kg 17Seeds 50 kg 1,676Herbicides 0.47 litres 197Insecticides 2.1 litres 880Transport 252 285Soybean yield 4,500 kg -Total inputs - 11,351Output - 30,545Energy inputs to produce 810 kg of bio-diesel from soybeansFactor Quantity MJElectricity 139,46 kWh 582Steam 697,384 kcal 2,920Cleaning water 82,562 kcal 348Internal heat 78,519 kcal 331Direct heat 227,296 kcal 951Losses 134,724 kcal 566Stainless steel 6.1 kg 365Steel 12 kg 553Cement 29 kg 230Total - 6,846Energy outputs in the production systemOutputs Quantity MJOil 810 kg 30,545Steam 3,690 kg 61,844Total Outputs 4500 kg 92,389Inputs Agricultural 11,690Industrial 6,846Total inputs - 18,197Overall balance(Outputs – inputs)- 74,192 (1: 5.1)Source: Rathmann et al., 2010.37
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Brazilian Biofuels Programmes from the WEL Nexus Perspective

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