The U.S. biofuel industry has grown dramatically in recent years, with production expanding from 1.6 billion gallons in 2000 to 9 billion gallons in 2008.¹ This dramatic increase can be attributed to the rise in production of corn-based ethanol and associated, smaller quantities of soy-based biodiesel. The number of refineries has also increased—from 54 in 2,000 to 170 in January 2009.² The worldwide economic recession and lower prices for petroleum have slowed the expansion of the industry, but because of strong state and federal mandates, production is expected to grow until production capacity reaches the federally mandated 36 billion gallons of biofuel in 2022.³

While energy prices, energy security, and climate change are front and center in the national media, these issues are often framed to the exclusion of the broader issue of sustainability—ensuring that the production and use of biofuels do not compromise the needs of future generations by recognizing the need to protect life-support systems, promote economic growth, and improve societal welfare. Thus, it is important to understand the effects of biofuel production and use on water quality and quantity, soils, wildlife habitat and biodiversity, greenhouse gas emissions, air quality, public health, and the economic viability of rural communities.⁴

Although corn-based ethanol is likely to continue to be a major contributor to U.S. biofuel supply in the near term, it is important to plan for the transition to advanced biofuels, such as agricultural resides (e.g., corn stover), perennial grasses and woody biomass, which are now almost universally viewed as preferable from a sustainability perspective. Decisions have been made at various levels of government to promote biofuels as a potential means of reducing greenhouse gases and enhancing economic development and energy security without a clear understanding of the economic, environmental, and social impacts of biofuel production and use.

While a number of studies have examined some of the environmental impacts associated with the expansion of biofuel production and use, most of these have focused at a national level. For example, the National Academies published a report assessing the water implications of biofuels⁵ and the World Resources Institute has also published a series of reports on the subject.⁶ However, many