BioFeed

An efficient and sustainable biomass feedstock production system is critical for the success of the biomass based energy sector. An integrated systems analysis framework to coordinate various feedstock production related activities is, therefore, highly desirable. This article presents research conducted towards the creation of such a framework. A breadth level mixed integer linear programming model, named BioFeed, is proposed that simulates different feedstock production operations such as harvesting, packing, storage, handling and transportation, with the objective of determining the optimal system level configuration on a regional basis. The decision variables include the design/planning as well as management level decisions. The model was applied to a case study of switchgrass production as an energy crop in southern Illinois. The results illustrated that the total cost varied between 45 and 49 $ Mg
1 depending on the collection area and the sustainable biorefinery capacity was about 1.4 Gg d
1. The transportation fleet consisted of 66 trucks and the average utilization of the fleet was 86%. On-farm covered storage of biomass was highly beneficial for the system. Lack of on-farm open storage and centralized storage reduced the system profit by 17% and 5%, respectively. Increase in the fraction of larger farms within the system reduced the cost and increased the biorefinery capacity, suggesting that co-operative farming is beneficial. The optimization of the harvesting schedule led to 30% increase in the total profit. Sensitivity analysis showed that the reduction in truck idling time as well as increase in baling throughput and output density significantly increased the profit.

Abstract: Unfavorable weather can significantly impact the production and provision of agriculture-based biomass feedstocks such as Miscanthus and switchgrass. This work quantified the impact of regional weather on the feedstock production systems using the BioFeed modeling framework. Weather effects were incorporated in BioFeed by including the probability of working day (pwd) parameter in the model, which defined the fraction of days in a specific period such as two weeks that were suitable for field operations. Model simulations were conducted for Miscanthus and switchgrass for values of pwd between 20 and 100% and intended biorefinery capacities between 1000 and 5000 Mg d–1; and the impact on total cost and farm machinery requirements was quantified. Results indicated that using production and provision systems designed assuming 100% pwd for lower pwd values increased the cost exponentially by up to 64% for Miscanthus and 85% for switchgrass. It also decreased the supportable biorefinery capacity for the collection region by up to 60%. If the systems were instead optimized for specific values of pwd, the original biorefinery capacity was maintained and the total cost increase was less than 5%. The resulting optimal systems required up to 40% higher investment in farm machinery. For Illinois, production systems designed for regional pwd values required a 34% increase in farm machinery investment for Miscanthus while only a 12% increase for switchgrass. Initiating Miscanthus harvesting in November instead of January reduced the farm machinery investment increase to 17%, which suggests that such an alternative should be rigorously evaluated.

Abstract: Distributed storage and pre-processing of biomass feedstock at satellite storage locations (storage
depots) has been proposed in literature to reduce costs and improve efficiency of the supply system. The performance of such a system, however, has not yet been rigorously quantified and compared with conventional alternatives. This work presents such an analysis using the BioFeed optimization model. BioFeed is a system-level model that optimizes the important feedstock production activities and determines the optimal system configuration on a regional basis. The BioFeed model was first modified to enable modeling of mechanical pre-processing, such as pelletization and grinding, at the input or the output of storage facilities, which can be mandatory or optional. The model was used to study different Miscanthus production scenarios in southern Illinois. The results showed that making storage pre-processing mandatory increased the total cost by up to 16–53% as compared to the base case. However, it reduced the farmers’ share of the total cost by up to 13–39%. The exact values depended on the particular pre-processing technology and scenario modeled. The most cost-effective system consisted of a combination of pre-processing on the farms as well as at the storage facilities. The study recommended that biomass output from a hammer mill should be the biorefinery delivery specification; the hammer mills should be installed at the input of the storage facilities, but pre-processing at the storage facility should be optional. This led to the minimum total cost of 46.4 $ Mg−1.