Ethanol Can Contribute to Energy and Environmental Goals

Abstract

To study the potential effects of increased biofuel use, we evaluated six representative analyses of fuel ethanol. Studies that reported negative net energy incorrectly ignored coproducts and used some obsolete data. All studies indicated that current corn ethanol technologies are much less petroleum-intensive than gasoline but have greenhouse gas emissions similar to those of gasoline. However, many important environmental effects of biofuel production are poorly understood. New metrics that measure specific resource inputs are developed, but further research into environmental metrics is needed. Nonetheless, it is already clear that large-scale use of ethanol for fuel will almost certainly require cellulosic technology.

Opportunities and roadblocks in utilizing forages and small grains for liquid fuels

“…These studies indicate that a single harvest system will likely optimize biomass-harvesting eYciency, but stand maintenance will determine harvesting periods. Net energy and economic studies recently completed by coauthors Vogel and Mitchell and others indicate that the net energy for switchgrass grown for cellulosic ethanol in Weld scale trials is similar to that estimated by Farrell et al [29] and the potential farmgate feedstock cost from the multilocation Weld trials averaged $0.17 L ¡1 ethanol. Based on this information, cellulosic ethanol from switchgrass is economically feasible and signiWcantly net energy positive.…”

Genome sequencing and analysis of the biomass-degrading fungus Trichoderma reesei (syn. Hypocrea jecorina)

“…Although replacement of gasoline with cellulosic ethanol may substantially reduce greenhouse gases in the atmosphere and decrease global warming 4 , the high cost of hydrolyzing biomass polysaccharides to fermentable sugars remains a major obstacle that must be overcome before cellulosic ethanol can be effectively commercialized. As the costs of cellulases and hemicellulases contribute substantially to the price of bioethanol, much cheaper sources of these enzymes are needed 5 .…”

Intérêts et limites des biocarburants de première génération

“…En France, une étude commanditée par l'ADEME et le ministère de l'industrie (ADEME/DIREM, 2002), a porté sur la première génération, tandis qu'une étude au niveau européen (EUCAR/CONCAWE/JRC, 2006) s'est aussi intéressée également aux biocarburants de deuxième génération, obtenus à partir de différentes ressources (résidus lignocellulosiques, bois, déchets de papeterie). Pour une même filière, les résultats de ces études varient fortement en fonction des hypothèses de calcul (périmètre du système évalué, méthode d'allocation) et de la représentativité des données utilisées, ce qui est source de controverses (Farrell et al, 2006). Toutefois, les études en cycle de vie concluent en général que les biocarburants actuels permettent de limiter l'utilisation d'énergie d'origine fossile et les émissions de GES par rapport aux carburants d'origine pétrolière.…”