Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2014
Publication Date: N/A
Interpretive Summary: Both corn grain and the remainder of the plant (stover) can be used for ethanol production. However, the manufacturing process is different for the two fractions. Most schemes for using both parts of the corn plant for ethanol involve separate harvest, storage, and transport of the two fractions. Unfortunately this results in multiple field operations and can result in stover that is contaminated with soil. In this study, we investigated harvesting and ensiling the whole plant in one operation as in making corn silage followed by separating the grain and stover by water floatation (grain sinks to bottom, stover floats on top), which could occur at the ethanol plant. The process worked well over a wide range of moisture contents, and pretreatment of the drier whole-plant corn using sulfuric acid was effective in making more of the corn fiber available for ethanol production. The whole-plant harvest and storage system was shown to be a viable alternative to conventional corn grain and stover systems for producing feedstocks for biochemical conversion, simplifying harvest and storage for farmers, and potentially reducing the cost of feedstock for ethanol producers.
Technical Abstract: This research investigated the harvest, ambient pre-treatment, and storage of whole-plant corn as an alternative to conventional systems whereby corn grain and stover are fractionated at harvest. Harvesting the whole-plant, both grain and most of the above ground stover, after physiological maturity can reduce the intense logistics challenges typically associated with corn harvest and expand the harvest window. To determine the feasibility of the proposed system, corn was harvested at 350 to 840 g/kg whole-plant dry matter (DM) using a forage harvester and then ensiled in pilot-scale silos. Ambient pretreatment during storage was investigated using both dilute acid and lime. Both pretreated and control whole-plant silages were well conserved during anaerobic storage with DM losses generally less than 40 g/kg. Hydrodynamic separation of the grain and stover fractions after storage was found to be more effective at fractionating starch and fiber than conventional dry grain harvest, and both fractions had desirable composition. The effects of pretreatment on the silage were pronounced at 30 and 100 g/kg DM sulfuric acid loading with less than 100 g/kg DM of the hemicellulose still bound in the cell wall at DM contents greater than 500 g/kg. The whole-plant harvest and storage system was shown to be a viable alternative to conventional corn grain and stover systems for producing feedstocks for biochemical conversion.