In spite of the abundant interest in conversion of agricultural products into useful energy carriers, there have been relatively few studies assessing the magnitude of the impact these fuels can make on satisfying US energy demands. There have been fewer studies of unintended consequences stemming from these enterprises, although several research groups have begun questioning the appropriate levels of subsidies provided to individuals and companies to stimulate production of bio-fuels. In this paper, the production capacities for bio-fuels-ethanol and biodiesel-are evaluated for their potential impact on the US energy market. Several ramifications of these technologies are reviewed. This study concludes that ethanol or biodiesel production do not appear scalable to make a significant difference on the US fossil fuel demand for transportation. Aspects of this study point to systemic changes that may be required in lifestyles and attitudes toward energy consumption. Finally, comments regarding US energy policies are included to stimulate discussion. (C) 2008 Elsevier Ltd. All rights reserved.