Biofuels From Perennial Grasses: Effects On Soil Properties and Implications On Water Use and Quality.

Increased global demand for renewable energy, particularly for renewable transportation fuels, has led to the evaluation and development of sustainable bioenergy cropping systems.  Current biofuel sources are largely derived from annual crops but competing demands for food and feed limits further, large-scale expansion. Perennial grasses are being evaluated as potential lignocellulosic feedstocks for an emerging cellulosic biofuel industry.  Perennial grasses in monocultures (e.g. Panicum virgatum L.; Miscanthus x giganteus) or in mixtures have shown environmental advantages over annual cropping systems.  Perennial grasses when used for conservation purposes have the ability to reduce nutrient and sediment runoff over annual cropping systems.  Recent evidence has shown positive impacts on soil properties when perennial grasses are managed as a bioenergy crop.  For example, dedicated herbaceous energy crops have shown large increases in soil carbon particularly at soil depth when grown on marginal croplands.  There is still uncertainty where perennial bioenergy crops will become economically viable and how they will be incorporated within a farming enterprise which will determine the overall impact on soil quality, water use, and water quality.   Total water use, when measured using a field to fuel tank model, will likely vary by conversion process.