Low-Moisture Switchgrass Bulk-Format Logistics Costs Based on Engineering Data
Logistics costs that spanned harvest, transport, storage, preprocessing, and year-round delivery of 371,870 dMg year-1 of milled, low-moisture switchgrass (SG) to a local biorefinery were determined for bulk-format versus round-bale systems. Separate spreadsheet analyses were conducted for three diesel fuel prices ($0.53 L-1, $0.92 L-1, and $1.32 L-1) because of the wide range of fuel prices during the project. A detailed analysis scenario identified a common harvest period, equipment annual use, other equipment uses, and protected SG storage on gravel pad, along with equipment performances based on previously published tests primarily for commercially available equipment. The bulk-format system used a depot equipped with stacker/reclaimer technology for storage, whereas the round-bale system used field-side bale stacks for storage, with both systems assuming 6% losses, primarily attributed to storage. Results indicated total costs for bulk-format versus round-bale systems of $54.63 per dry Mg (dMg-1), $60.41 dMg-1, and $66.21 dMg-1 versus $54.59 dMg-1, $62.10 dMg-1, and $67.93 dMg-1 corresponding with diesel fuel costs of $0.53 L-1, $0.92 L-1, and $1.32 L-1, respectively. The most significant bulk-format system total cost of $22.79 dMg-1 was associated with a stacker/reclaimer, conveyance, and dust collection at the depot, which was 42% of total costs at a diesel fuel cost of $0.53 L-1. For the round-bale system, bale chopping total costs was highest and represented an average of 27% of total costs, with costs ranging from $14.63 dMg-1 to $19.08 dMg-1 for diesel fuel input costs ranging from $0.53 L-1 to $1.32 L-1, respectively. For comparison, the forage harvester provided harvesting and chopping in the bulk-format system at total costs ranging from $6.47 dMg-1 to $8.80 dMg-1 across the same range of diesel fuel input cost. The forage harvester provided an economic advantage in size reduction compared to tub grinding. Truck hauling for both the bulk-format and round-bale systems represented significant expenses at all selected fuel costs. In addition, the multiple times that round bales were handled represented accumulating costs that were sensitive to diesel fuel costs.