Abstract
Adding bioenergy to the US energy portfolio requires long-term profitability for bioenergy producers and the long-term protection of affected ecosystems. In this study, we present steps along the path towards evaluating both sides of the sustainability equation (production and environmental) for switchgrass (Panicum virgatum) using the Soil and Water Assessment Tool (SWAT). We modeled production of switchgrass and river flow using SWAT for current landscapes at a regional scale. To quantify feedstock production, we compared lowland switchgrass yields simulated by SWAT with estimates from a model based on empirical data for the eastern US. Geographic patterns were very similar. Average yields reported in field trials tended to be higher than average SWAT-predicted yields, which may nevertheless be more representative of production-scale yields. As a preliminary step toward quantifying bioenergy-related changes in water quality, we evaluated flow predictions by the SWAT model for the Arkansas-Red-White river basin. Monthly SWAT flow predictions were compared to USGS measurements from 86 subbasins across the region. Although agreement was good, analysis of residuals (functional validation) identified patterns to guide future improvements. Our next step will be to continue model improvement, after which we will forecast changes in water quality associated with incorporating bioenergy crops into future landscapes. This analysis will help us, in future, to identify areas with the highest economic and environmental potential for feedstock production.
