Energy Demands and Other Environmental Impacts across the Life Cycle of Bioethanol Used as Fuel

摘要

Most assessments of converting biomass to fuels are limited to energy and greenhouse gas (GHG) balances to determine if there is a net loss or gain. A fairly consistent conclusion of these studies is that the use of bio-ethanol in place of conventional fuels leads to a net gain. However, the findings of a recent literature review indicate that basing fuel production policy on environmental sustainability studies that are life cycle based but that ignore other issues are likely to result in unintended, and possibly detrimental, shifting of environmental burdens. Human and ecological health impacts need to be weighed into the decision-making process along with climate change and resource depletion concerns. Acidification, human toxicity and ecological toxicity impacts, mainly occurring during the harvesting and processing of the bio-mass, were more often unfavourable than favourable for bio-ethanol. This paper summarizes the findings of a literature search that was recently conducted and revealed 45 publications (1996-2005) that compare bio-ethanol systems to conventional fuel on a life-cycle basis, or using life cycle assessment. Feedstocks, such as sugar beets, wheat, potato, sugar cane, and corn, have been investigated in many countries, including Brazil, Canada, India, the Philippines, South Africa, the United States and several European nations. Studies are needed to fill the critical gaps, especially on ethanol from tropical sugar crops, cellulosic cropped feedstocks, particularly perennial grasses, and corn.