Optimal Location of Cellulosic Ethanol Facilities and Their Impacts on Surface Water Quality in the Southeastern United States

Research suggests that by 2022, 10.5 billion of the 21 billion gallon annual production target for advanced biofuels mandated by the expanded 2007 Renewable Fuel Standard (RFS2) could originate in the Southeastern United States (US) (USDA 2010). This study applied a biorefinery siting and feedstock optimization model and a water quality model to examine the ex-ante impact of biorefinery locations on agricultural input use and nitrogen (N) loading into the region’s hydrological system. The objective of this research is to understand the potential implications of this level of cellulosic ethanol production and concomitant changes in land use on surface water quality at local and regional scales.

Least-cost cellulosic biorefinery locations and associated conversion of agricultural land to switchgrass production were projected for the South Atlantic Coast, the Eastern Gulf Coast, and Tennessee river basins, collectively referred to as the SAGT River Basin. Two industry configurations and four levels of cellulosic ethanol production were considered, including 22%, 31%, 50%, and 100% of the 10.5 BGY target for the Southeastern US. Stream level N concentration and the percentage of N flux attributed to agricultural fertilizer applications were predicted under the two industry configurations at each production level using the US Geological Survey’s SPARROW hydrological model. Outcomes were compared to 2009 baseline stream system nutrient levels to determine agriculture’s contribution to total N loadings and the impact of land use change on the region’s surface water quality at each level of cellulosic ethanol production. The net effect across the region are increases in the mean stream level N concentration and agricultural N source share under both industry configurations (12.95% and 18.63%, respectively, at 100% of target under industry configuration A, and 10.16% and 29.85%, respectively, under industry configuration B), relative to the baseline. Changes were primarily driven by the conversion of hay/pastureland and soybeans into more fertilizer intensive industrial switchgrass production.