The finitude of fossil fuels, concerns for energy security and the need to respond to climate change have led to growing worldwide interests in biofuels. Biofuels are viewed by many policy makers as a key to reducing reliance on foreign oil, lowering emissions of greenhouse gases and meeting rural development goals. However, political and public support for biofuels has recently been undermined due to environmental and food security concerns, and by reports questioning the rationale that biofuels substantially reduce carbon emissions. We discuss the promise of biofuels as a renewable energy source; critically evaluate the environmental and societal costs of biofuel use; and highlight on-going developments in biofuel. feedstock selection and production technologies. We highlight net positive greenhouse gases emissions, threats to forests and biodiversity, food price increases, and competition for water resources as the key negative impacts of biofuel. use. We also show that some of these environmental and societal costs may be ameliorated or reversed with the development and use of next generation biofuel feedstocks (e.g., waste biomass) and production technologies (e.g., pyrolysis). We conclude that certain types of biofuels do represent potential sources of alternative energy, but their use needs to be tempered with a comprehensive assessment of their environmental impacts. Together with increased energy conservation, efficiencies and technologies such as solar-power and wind turbines, biofuels should be included in a diverse portfolio of renewable energy sources to reduce our dependence on the planet's finite supply of fossil fuels and to insure a sustainable future. (c) 2008 Elsevier Ltd. All rights reserved.
