Cost to produce and deliver cellulosic feedstock to a biorefinery: Switchgrass and forage sorghum

Switchgrass and forage sorghum have both been proposed as potential candidates for high yielding, dedicated energy crops. This research was conducted to determine and compare the costs to produce and deliver switchgrass and forage sorghum biomass under the assumptions that the biomass would be baled and transported by truck and that the biorefinery would use either switchgrass or forage sorghum but not both. A multi-region, multi-period, monthly time-step, mixed integer mathematical programming model is used to determine the costs to deliver a flow of biomass to a biorefinery. The model is designed to determine the optimal location of a biorefinery that requires 3630 Mg of biomass per day, the area and quantity of feedstock harvested in each county by land category, the number of harvest machines required, and the costs to produce, harvest, store, and transport a flow of biomass to a biorefinery. The estimated costs of land rent, establishment, maintenance, fertilizer, harvest, storage, and transportation is $60 Mg−1 for switchgrass and $74 Mg−1 for forage sorghum. The cost difference between the two crops is primarily due to harvest costs, which are estimated to be $13 Mg−1 greater for forage sorghum. Forage sorghum has a narrower harvest window, requires more time for field drying prior to safe baling and, as a consequence, requires significantly more harvest machines. Based on the assumptions used in this study for Oklahoma conditions, a switchgrass system with a nine-month harvest window can deliver baled biomass at a lower cost than a forage sorghum system with a five-month harvest window. However, the value of a Mg of switchgrass relative to a Mg of forage sorghum remains to be determined.