Roadside Vegetated Filter Strips to Simultaneously Lower Stormwater Pollution Loadings and Improve Economics of Biorefinery Feedstocks

Green infrastructure, such as vegetated filters strips (VFSs), can reduce roadway runoff pollution while also producing biomass for biochemical and biofuels. As part of a larger effort advancing ecosystems services, including clean water recovery, within the bioeconomy, we evaluated roadside VFS installation for improving the economics of biofuels feedstock. Poplar trees were selected as feedstock due to their (a) ability to grow on marginal soils without added fertilizers, (b) ability to transpire large volumes of water, (c) amenability to short-rotation coppice – a process that leaves roots in place for re-growth, and (d) high sugar content for biofuel/biochemical production. Two metrics were calculated: (1) the mass and cost of poplar produced on the VFS, and (2) the reduction in stormwater pollutants. Forecasting used GIS spatial analysis, with western Washington State as the study area. Roadside sites identified by GIS could support production of 97 dry Gg per year of poplar biomass. Cumulative feedstock costs (primarily from transportation) were determined starting with the sites with lowest cost. The results showed that combining VFS poplar with dedicated tree farms reduced feedstock costs resulted in a more economically viable biorefinery. Environmental impact analysis showed that half of urban roadways and one-third of rural roadways associated highly sensitive aquatic habitats were amenable to VFS, where VFS provided substantial reduction in total loadings for TSS, copper, zinc, phosphorus, nitrogen, and lead. This work expands approaches combining GIS and economic analysis for simultaneous cost and environmental benefits during development of non-traditional land for bioenergy crop production.