Modeling Air Quality Impacts of Feedstocks Transportation for Cellulosic Biofuel Production in Tennessee

This study estimates the plant-gate cost and hauling emissions of supplying two different biomass feedstocks, a perennial grass (switchgrass) and an annual energy crop (energy sorghum), for biofuel production in Tennessee. This study first applied a spatial-oriented mixed-integer mathematical programming model using geographic information system (GIS) data to generate a least-cost solution of the feedstock supply system and the location of a single-feedstock biorefinery in three different regions of the state, i.e. east, central and west Tennessee. Based on the feedstock draw area and the road links for hauling feedstock to the biorefinery in each region determined in the model, U.S. Environment Protection Agency’s Mobile Vehicle Emission Simulator (MOVES) model was then used to estimate the baseline emissions for 2010 in the study region and additional emissions generated from hauling feedstock. Results showed that the degree of feedstock draw area dispersion and topography of draw area around the biorefinery site have important impact on the emissions produced from hauling feedstock to the biorefinery. Based on feedstock plant-gate cost and hauling emissions, switchgrass is more suitable than energy sorghum for biofuel production in Tennessee. The larger draw area associated with energy sorghum creates higher vehicle travel miles, resulting in more transportation costs and hauling emissions to the biorefinery. The biorefinery with the most economic feedstock cost and the least feedstock hauling emission is suggested to be sited in Robertson County in central Tennessee.