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A REVIEW OF ASSESSMENTS CONDUCTED ON BIO-ETHANOL AS A TRANSPORTATION FUEL FROM A NET ENERGY, GREENHOUSE GAS, AND ENVIRONMENTAL LIFE CYCLE PERSPECTIVE
Citation:
VON BLOTTNITZ, H. AND MARY ANN CURRAN. A REVIEW OF ASSESSMENTS CONDUCTED ON BIO-ETHANOL AS A TRANSPORTATION FUEL FROM A NET ENERGY, GREENHOUSE GAS, AND ENVIRONMENTAL LIFE CYCLE PERSPECTIVE. D. Huisingh (ed.), JOURNAL OF CLEANER PRODUCTION. Elsevier Science Ltd, New York, NY, 15(7):607-619, (2007).
Description:
Interest in producing ethanol from bio-mass in an attempt to make transportation ecologically sustainable continues to grow. In recent years, a large number of assessments have been conducted to assess the environmental merit of biofuels. Two detailed reviews that looked at the sustainability of biofuels present contrasting results: one is generally unfavourable, while the other is more favourable toward biofuels. However, most work that has been done thus far to assess the conversion of specific feedstocks to biofuels, specifically bio-ethanol, has not gone beyond energy and carbon assessments. This study draws on 47 published assessments that compare bio-ethanol systems to conventional fuel on a life-cycle basis, or using life cycle assessment (LCA). A majority of these assessments focused on net energy and greenhouse gases, from which the following general lessons emerge: make ethanol from sugar crops, in tropical countries, but consider expansion of agricultural land with extreme caution; hydrolyse and ferment lignocellulosic residues but only when alternatively replaced electricity is fairly green and; the LCA results on grasses as feedstock are insufficient to draw conclusions. It appears that technology choices in process residue handling and in fuel combustion are key, whilst biodiversity issues should best be handled by site-specific environmental management tools. Seven of the reviewed studies evaluated a wider range of environmental impacts, including resource depletion, global warming, ozone depletion, acidification, eutrophication, human and ecological health, smog formation, etc., but came up with divergent conclusions. These LCAs typically report bio-ethanol resulting in reductions in resource use and global warming; however, impacts on acidification, human toxicity and ecological toxicity, occurring mainly during the growing and processing of bio-mass, were more often unfavourable than favourable. It is in this area that further work is needed.