Cost minimization of supplying biomass for ethanol biorefineries

A major hurdle facing commercial biofuel production is the cost of producing the feedstock. Since biofuel feedstock is bulky in nature, a large proportion of cost needed to be allocated for harvesting and transportation of feedstock. Economic viability of ethanol production from cellulosic feedstock depends in part of the cost to produce, harvest and deliver feedstock to the ethanol production facilities. A well-developed harvesting and transportation system does not exist for most feedstock. Hence to determine accurate estimation of the harvest, transportation and storage costs is important in ethanol production. The objectives of the study are to determine the optimal harvesting unit for ethanol biorefinery and estimate harvesting, storage and transportation costs of switchgrass under various harvesting schedules. A biorefinery with the annual capacity of processing 4.16 million gallons of ethanol was considered. Based on average dry matter yield, total production area needed for annual harvesting was estimated. The harvesting units needed for the continuous harvest and supply of biomass were estimated based on information on the capacity of machineries etc. Accordingly various costs associated with operating and maintaining harvesting unit were estimated. Transportation units needed were estimated for continuous supply of feedstock to the refinery and the associated costs were calculated. The number of machinery needed for a harvesting unit for the 90 day harvesting schedule are the most while year round harvesting schedules needs lesser number of machinery for a harvesting unit. Harvesting switchgrass in 90 day schedule is the most expensive scenario with all harvesting, hauling and storage costs added together. Year round harvesting schedule occurs as the least costly scenario. Sensitivity analysis shows the positive trend for harvesting and hauling costs to biomass yield, ethanol conversion technology, distance and decreasing trend for the range of truck speed considered. The results generated in this study will be useful in designing optimal harvest schedule of biomass for ethanol biorefinery