Biofuels can play a very important role to diversify the energy supply in the transportation sector, currently almost fully based on fossil fuels. In this context, the production and use of different biofuels have been increasing around the world. Nowadays, the biofuels produced and consumed in large quantity are ethanol from sugar and amylaceous biomass and biodiesel from vegetable oils and animal fats, which substitute gasoline and diesel oil, respectively. In 2010, the global biofuels production reached 114 billion liters, of which around 15% corresponded on biodiesel. A relevant issue associated to biofuels adoption is related to their effective sustainability of biofuels, in comparison to the conventional fuels. In this context, the objective of this study was to evaluate and compare the main environmental impacts and energy flows of ethanol from sugarcane and biodiesel from soybean and palm oil, in Brazilian conditions, with their respective fuels substitutes (gasoline and diesel). The methodological tool used was the Life Cycle Analysis (LCA), in well-to-tank assessment. In addition, the results were compared by meta-analysis of previous published studies from others countries. The environmental analysis was done using the software SimaPro 7.0.1 and the CML 2 baseline 2000 methodology, developed by the University of Leiden. The environmental impacts were quantified and ranked in impact categories. Such ranking helped to identify and quantify the major impacts of the system and in each stage and proposing ways to reduce them. Finally, the results of the inventory analysis and the impact assessment were discussed. It was observed that production systems with higher agricultural yields and allows the use of co-products in its cycle had best results.

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