Characterization of the Impact of Process Variables on the Densification of Corn Stover
The bulk density of corn stover poses a major obstruction to its large scale viability as a biomass feedstock. Corn stover has a low bulk density which limits transportation and storage containers based on volume rather than weight, creating large inefficiencies during the harvest, transport, and storage phases of corn stover production. Producing a densified stover product during the harvest phase of production could reduce the overall production cost of corn stover.
Corn stover can currently be densified by grinding, baling, briquetting, or pelleting methods. Grinding systems do not produce an adequate bulk density to optimize transportation requirements alone, and are often used as a pre-processing operation for other densification systems. Baling can provide an improved bulk density at low energy requirements, but faces a logistical challenge associated with handling individual bales. Pelleting and briquetting systems generally require grinding as an initial process, and provide a high quality densified stover product at low mass flow rates and very high energy requirements. All of these factors drive up the production cost of densified corn stover for each system.
This research investigated a densification method that outputs a large, tapered and cylindrical, densified stover product. This research differentiates itself from previous briquetting and pelleting work because these briquettes are produced at field harvested particle sizes and lower compression pressures. While this produces a lower quality and density briquette than traditional briquetting and pelleting processes, the energy requirement is significantly reduced. This type of densified corn stover product could be suitable for in-field single-pass corn stover harvesting systems where the material is harvested and stored until further processing (the densified product is not the final product).