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On-Farm Biomass Processing: Towards an Integrated High Solids Transporting/Storing/Processing System
S.E. Nokes, M. Montross, R. Anex, C. Crofcheck, S. DeBolt, M. Flythe
Department of Biosystems and Agricultural Engineering
Farms have two valuable resources at their disposal to achieve economical biomass conversion; the infrastructure to store (and potentially process) biomass and the storage time to accomplish the biomass conversion processes using alternatives with less environmental impact relative to centralized facilities.
This project will develop an integrated material handling/biomass conversion approach for the production of biofuels that is structured to fit within the existing agricultural paradigm. The proposed integrated process can be distributed regionally with only minor modifications to equipment and facilities.
Biomass feedstocks investigated include switchgrass, miscanthus, corn stover, and wheat straw. This project will develop a baling system with bales of density suitable for on-farm biomass conversion. The baling system will be a single-pass system for agricultural crop residues and energy crops. Best management practices that maximize biomass production, while minimizing environmental impacts will be developed for biomass energy crops, as well as for vegetative buffers in conventional cropland and as new crops on marginal/abandoned land.
The proposed biomass conversion process steps, the pretreatment of the biomass, are scaled to the farm, employing a modified bunker silo as the reactor and taking advantage of the high density feedstock bales to increase production efficiency. After pretreatment, solid substrate cultivation with mobile phase replacement will be performed using a co-culture of a cellulolytic organism and a solventogenic organism. Temperature control within the reactor will be maintained using recycled water heated by gasification of the residual feedstock. The products will be concentrated and separated from the recycled aqueous stream using either modular, stand-alone membrane or adsorption technologies. Thus, the volume of the value-added product shipped to a biorefinery for further upgrading is greatly reduced.
Life cycle analysis models will be integrated with geographic information systems (GIS), economic, and environmental models to evaluate a range of management strategies, feedstocks, regional impact, land suitability, and potential fossil fuel displacement. Biomass processing models will be developed to evaluate alternative off-farm processing options and their potential impact on bioenergy production. Economic and environmental analyses will be used to determine the level of incentives required to increase bioenergy production and protect the environment when these goals conflict with maximum farm profitability.
We expect the system to allow farmers or cooperatives to produce biofuels and biochemicals s cost competitively with petroleum. These products will be concentrated on-farm so that the product stream will be economical to transport to a refinery to be further upgraded, largely eliminating the high cost of transporting raw biomass. In addition, the biomass will be supplied in a sustainable manner that will not increase soil erosion or net greenhouse gas emissions, yet will still maintain farm profitability.