Water Quality and Quantity Implications of Biofuel Intercropping at a Regional Scale.

Because of a strong national interest in greater energy independence and concern for the role of fossil fuels in global climate change, biofuels have become important for transportation.  The U.S. government has mandated production of 36 billion gallons of renewable fuels by 2022, which compromises 15 % of U.S. liquid transportation fuels.  Unfortunately, large-scale production of corn-based ethanol requires large amounts of water and generally has detrimental effects on water quality such as erosion and excess runoff and leaching of nitrogen and phosphorus from cornfields.  Production of cellulosic biomass offers a promising alternative to corn-based.  The cultivation of switchgrass, using standard agricultural practices, is one option being considered for the production of cellulosic biomass. Recently, producers have explored the possibility of intercropping cellulosic biofuel crops within managed forests. There are some uncertainties with cellulosic biofuel production and that basic information such as water or nutrient inputs and outputs, impact on soil erosion, and overall yields need to be examined in the context of regional scales. We used the Soil Water Assessment Tool, a physically-based hydrologic model, to examine water quality and quantity effects of intercropping switchgrass in managed loblolly pine plantations in the southeastern U.S.  We examined various land use change scenarios from conversion of a small percentage of managed forest land to pine/switchgrass intercropping to all managed forested land converted to switchgrass.  Our results will be essential to managers as they plan for large-scale production or cellulosic biofuels while sustaining water quality and quantity.