Water quality impact assessment of large-scale biofuel crops expansion in agricultural regions of Michigan

The challenges we face in transitioning to a global production of biomass as renewable feedstock sources in a way that is both economical feasible environmentally sustainable are ubiquitous. In this study, the Soil and Water Assessment Tool (SWAT) was used to predict the possible long-term environmental implications, specifically water quality, due to large-scale bioenergy cropping system expansion based on four landuse scenarios and 15 bioenergy crop rotations for four watersheds, totaling 244 model simulations. The study area consists of four watersheds totaling 53,358 km2 located in Michigan. The results suggest that perennial grass species are the most suitable for large-scale implementation, whereas traditional intensive row crops should be implemented with caution on such a broad scale. Row crops also had the highest increases of high priority areas for sediment, nitrogen, and phosphorus. Based on the data from this study, it is not recommended that marginal land be converted to any bioenergy rotation in areas with preexisting high nitrogen levels. Statistical analyses demonstrate that perennial grass species significantly reduce sediment on all lands except marginal lands. With the exception of row crops cultivated on marginal lands and all agricultural land, the majority of bioenergy crops significantly reduce total phosphorus loads.

► We used a watershed model to evaluate environmental impact of bioenergy crop expansion.
► We examine changes in high priority areas and stream reaches due to changes in pollution load.
► In general, perennial grasses improve and row crops deteriorate watershed health.
► This study will aid in environmental decision-making for large-scale landuse planning.