A GIS-based Multi-objective Optimization of a Lignocellulosic Biomass Supply Chain: A Case Study in Tennessee

To achieve an economically and environmentally sustainable lignocellulosic biomass (LCB)-based biofuel industry sector, the design and location of a sustainable LCB supply chain is important. In this study, a multi-objective optimization model integrated with high-resolution geographical data was developed to examine the optimal switchgrass supply chain for a potential biorefinery in Tennessee, specifically evaluating the potential tradeoffs between the objectives of minimizing plant-gate cost and GHG emissions from the switchgrass supply chain. The key findings of this study are as follows: both plant-gate feedstock cost and GHG emissions were sensitive to the type of land converted into switchgrass production, the type of land use change also affected the density of the feedstock supply region due to the spatial heterogeneity in the availability of different types of land, hence affecting transportation-related cost and GHG emissions, and a tradeoff relationship was discovered between cost and GHG emissions for the switchgrass supply chain, primarily driven by the type of land converted.

As a result of land use changes and transportation distances, the imputed cost to reduce one unit of GHG emissions was initially modest; however, the imputed cost increased considerably when the supply chain GHG emissions were further mitigated. This implied that the location of switchgrass production and the resulting changes in crop production should be considered in targeting government incentives to encourage switchgrass-based biofuel production in the state and the southeastern region. Sensitivity analyses indicated that the dry matter loss (DML) decomposition, if considered as a source of GHG emissions, would considerably increase the supply chain GHG emissions. Different harvest and storage technology used in the feedstock supply chain altered the DML rate and corresponding GHG emissions however did not change the tradeoffs between the two objectives significantly. The consideration of GHG emissions from cattle relocation, on the other hand, appears to reduce the GHG emission level of the supply chain to a great extent and change the tradeoff relation between the two objectives.