Environmental Consequences of Biofuel Feedstock Production: Soil, Water, and Air Quality.

Current U.S. plans for energy security rely on converting large areas of cropland from food to biofuel production. Additionally, lands currently considered too marginal for intensive food production may be considered suitable for biofuel production; predominant cropping systems may shift to more varied arrays including novel species for which little agronomic and environmental data exist. U.S. agriculture has extensive experience with intensive maize production and much recent discussion on energy from plants has focused on simply repurposing the existing farming systems towards ethanol instead of or in addition to animal feed.  Both the grain and the stover can be used in energy production, but removing the majority of the aboveground biomass from a farm field may negatively impact air, soil, and water quality.  Herbaceous perennials including novel species such as Miscanthus imported from Europe and low-input native systems may offer key advantages over maize production.  Farmers can use existing farm equipment and these systems are expected to require far fewer energy and financial inputs than annual row crops.  However, at present, research on N and C cycling in these candidate biomass systems is fragmented and incomplete, a critical barrier to profitable and environmentally benign on-farm implementation of the U.S. biofuel agenda.  Likewise, understanding crop water balance and optimizing water use efficiency will be essential to renewable biofuel success as water is expected to be the single, most limiting factor that transcends the multiple agro-ecozones in which U.S. biofuel production will be pursued.  Sustainable production with concomitant protection or improvement of air, soil and water resources requires improved knowledge of comparative production potentials and environmental impacts of biofuel cropping systems. Positive and negative impacts these shifts may have on soil, water, and air quality will be presented and the limitations of existing scientific knowledge will be analyzed to identify critical gaps.