Grey Water Footprint and Economic Tradeoff Analysis of Switchgrass Supply Chain: A Case Study of West Tennessee

Groundwater has been one of the major water resources in west Tennessee. The aquifers in west are at risk of contamination associated with the public water supply and agricultural use, which jeopardized the drinking water sources. Given its ecological and environmental advantages in less pollution pressure from lower fertilization intensity and less irrigation demand, switchgrass has been considered as a potential feedstock for biofuel industry in the United States. Therefore, large-scale production of switchgrass in Tennessee as a biofuel feedstock could reduce nitrate loadings to groundwater; hence lowering the nutrient pollution associated with agricultural production. However, the low efficiency of storage and transportation in the feedstock supply chains has hindered the commercialization of a switchgrass-based biofuel industry. Thus, the objective of this study is to determine the tradeoff relation between economic cost and aquatic environmental benefit measured as mitigated grey water footprint in a switchgrass supply chain design. An augmented epsilon constraint multi-objective optimization model was applied to high-resolution spatial data in determining the optimal placement of the feedstock supply chains. Results showed that land change into switchgrass production is crucial to both plant-gate cost and aqueous environmental impact based on crop types and ambient water quality condition. Tradeoff between feedstock costs and water quality improvement in switchgrass supply chains is associated mainly with the changes of land use. The most preferred solution plan generated at 5% increase in feedstock cost but lower the nitrate loading and the grey water footprint greatly in the feedstock supply chain compared with cost minimization baseline scenario.