Techno-Economic Impact of Diesel Fuel, Labor, AND Interest Rates on Bulk-Format and Round Bale Logistics Expenses for Switchgrass

摘要

Deterministic cost analyses were conducted for a harvest, storage, preprocessing, and supply system providing 371,870 dry Mg (dMg) year' of milled switchgrass (SG) to a biorefinery from 21,929 ha ofproduction fields within 72 km of the biorefinery. Varied input costs of diesel fuel, labor, and interest rate were input into a highly detailed cost analysis for bulk-format and baseline round bale logistics. These operational input factors, potentially refiecting an evolving economic climate or paradigmshift, were examined to provide insight into the cost to deliver preprocessed biomass feedstock for centralized commercial-scale conversions. Total annual costs per dry unit of SG were determined for all combinations of diesel fuel prices of $0.53 L~(-1), $0.92 L~(-1), and $1.32 L~(-1) total labor costs of $20.00 h~(-1), $28.85 h~(-1), and $40.00 h~(-1) singly and uniformly applied across all labor inputs; and three representative interest rates of 6%, 8%, and 12%. Increases in total cost most dependedon increases in diesel fuel cost, followed by labor rate, and finally interest rate. Increases in fuel costs from $0.53 L~(-1) to $1.32 L~(-1) yielded a total cost increase of about $11.56 dMg~(-1) and $13.36 dMg~(-1) for bulk-format and round bale logistics, respectively, for all combinations of labor and interest rates. The overall increase in labor rate ($20.00 h~(-1) to $40.85 h~(-1)) resulted in increased total costs of about $10.32 dMg~(-1) for bulk-format logistics and $9.94 dMg~(-1) for round bale logistics for all fuel and interest rates. The overall increase in interest rate (6%, to 12%)) resulted in increased total costs of about $6.72 dMg~(-1) for bulk-format logistics and $4.21 dMg~(-1) for round bale logistics for all fuel and labor rates. Increases in total costs for combined increases in fuel cost, labor rate, and interest rate were $28.60 dMg~(-1) and $27.48 dMg~(-1), yielding maximum total costs of $87.87 dMg~(-1) and $86.53 dMg~(-1) for bulk-format and round bale logistics, respectively. Costs were determined for existing equipment systems, including novel use of waste compaction and ejector semi-trailers. The highest potential for cost reductions may require clean-sheet equipment designs specifically tailored for SG, such as forage harvesters that direct-cut standing SG, mobilized stacker-reclaimer technology to not inhibit stack-area footprint, selficompacting ejector trailer technology, and bale grinding technology incorporating controlled mass feeding and shear failure elements.