An inventory control model for supplying biomass to a processing facility

An inventory control model was developed to determine the least cost approach for supplying biomass to a processing plant. Model applications were made for the plantation, harvest, and manufacturing components of woody biomass to ethanol supply systems to assess efficiency and financial performance. Model solutions determined the optimum inventory policy for hybrid poplar plantations grown over rotation lengths of 4 through 8 years. The harvest occurred during a 6 month time frame after the growing season. All biomass was directed to an ethanol manufacturing facility capable of processing 10,000 tonnes of harvested raw materials per month. At this level, the facility was required to meet an output demand of just over 3,000,000 litres per month. An evaluation of model solutions led to an optimum biomass rotation length of six years and an ethanol production cost of $0.376 per litre. The least-cost policy established the harvesting requirements and storage schedules for standing trees, harvested raw materials, and ethanol. Inventory control had a major impact on production costs, with alternate strategies within the rotation increasing ethanol costs by as much as 62%. If biomass is to compete as a viable feedstock for alternative fuel or chemical production, additional cost reductions will be necessary. These can be realized through the inventory control of standing trees, harvested materials, and final product.