A novel approach to producing corn stover biomass feedstock has been investigated. In this approach, corn grain and stover are co-harvested at moisture contents much less than typical corn silage. The grain and stover are conserved together by anaerobic storage and fermentation and then separated before end use. When separated from the stover, the moist, fermented grain had physical characteristics that differ from typical low-moisture, unfermented grain. A comprehensive study was conducted to quantify the physical properties of this moist, fermented grain. Six corn kernel treatments, either fermented or unfermented, having different moisture contents, were used. Moist, fermented kernels (26 and 36% w.b. moisture content) increased in size during storage. The fermented kernels’ widths and thicknesses were 10% and 15% greater, respectively, and their volume was 28% greater than the dry kernels (15% w.b.). Dry basis particle density was 9% less for moist, fermented kernels. Additionally, the dry basis bulk density was 29% less, and the dry basis hopper-discharged mass flow rate was 36% less. Moist, fermented grain had significantly greater kernel-to-kernel coefficients of friction and angles of repose compared to relatively dry grain. The friction coefficient on four different surfaces was also significantly greater for fermented kernels. Fermented corn kernels had lower individual kernel rupture strengths than unfermented kernels. These physical differences must be considered when designing material handling and processing systems for moist, fermented corn grain.

Highlights Cutting height and harvest date were used to alter stover moisture content, yield, and composition. Anaerobic co-storage of grain and stover limited losses to less than 6% of dry matter. Extent of fermentation was greater for higher moisture stover than grain, but total acids were less than 5 g kg-1. Reducing the harvester cutter head rotational speed resulted in a greater fraction of whole corn kernels. Abstract. This research investigated the utility of co-harvesting and anaerobic co-storage of corn grain and stover to positively influence their physical and chemical characteristics as a biomass feedstock. Corn grain and stover were harvested in 2019 and 2020 with a self-propelled forage harvester. Stover yield, moisture content, and composition were altered by the harvest date, stubble height, and header configuration. Harvest date had the utility of varying the stover moisture content (p < 0.001) from 42.3% to 53.5% (w.b.) and 43.1% to 53.9% (w.b.) for the 2019 and 2020 harvest years, respectively. Stubble height was also utilized to vary stover moisture content. A negative linear relationship was established between stubble height and stover moisture content for the early (R2 = 0.76) and late harvest (R2 = 0.91) dates for both years. Stover yield also showed a negative linear relationship (R2 = 0.76) with stubble height over both years. Regardless of the stubble height, the row-crop header collected more stover (p < 0.001) than the ear-snapper header. In 2020, harvested stover ranged from 5.0 to 10.5 Mg ha-1, with ha-1 representing 41% to 85% of the total available stover. In both years, stover ash content was less than 64 g kg-1. Material stored in pilot-scale silos (19 L) was well conserved during anaerobic storage, with average DM losses of 4.8% and 3.4% in 2019 and 2020, respectively. Grain moisture content averaged 23.6% (w.b.) at harvest, and 31.0% (w.b.) after storage as moisture migrated from the moist stover to the drier grain. Harvesting whole-plant corn with a forage harvester had the unwanted effect of reducing the particle size of the grain fraction, which would complicate downstream utilization. However, reducing the harvester cutterhead speed increased the fraction of intact kernels from 47% to 85% by mass. The studied system was a viable alternative to conventional corn grain and stover systems for producing feedstocks for biochemical conversion. Keywords: Ash, Ensiling, Ethanol, Maize.

Whole-plant corn has been previously investigated as a biomass feedstock. Current approaches are analogous to harvesting whole-plant corn for livestock feed or biogas production. They include utilizing a self-propelled forage harvester to harvest the plant as a bulk material and storing it anaerobically. This process leads to grain damage, reducing the marketability of the grain after fractionation. This work investigated a process that included harvesting and anaerobically storing whole-ear corn with corn stover as an alternative. Over two harvest seasons, dry matter losses, moisture content changes, and grain damage were assessed after anaerobic storage. Less than 3% grain damage was observed across all treatments. Stover moisture decreased by 3% to 7% wet basis. Depending on the harvest year (p < 0.001), grain moisture content increased by 7 to 10 percentage points wet basis (p = 0.012). Cob moisture increased by about four percentage points wet basis regardless of harvest year (p = 0.49). Dry matter losses for the overall treatment were less than 3% across both harvest seasons, but high variability was observed when reviewing the losses in the ear and stover fractions. Based on this work, whole ear storage should be considered where subsequent grain fractionation and the marketability of the grain fraction are a concern.

HighlightsA screenless hammermill utilizing impact and shredding was used to process wilted alfalfa.Processing increased specific surface area and ruptured plant cells as quantified by a processing level index.Processed material was more compliant than the chopped material resulting in 26% to 56% greater compacted density.Processing reduced silage pH and increased fermentation acids compared to the chopped silage.Abstract. Intensive mechanical processing of wilted alfalfa could potentially increase ruminant utilization of alfalfa. A novel forage processing mechanism which combines impact and shredding was used to investigate intensive physical disruption of wilted alfalfa. Physical disruption was quantified by a processing level index (PLI) defined as the ratio of treatment leachate conductivity relative to that of an ultimately processed treatment. Utilizing this index, four processing levels defined by the number of passes through the processor were compared to a control treatment of conventionally chopped material. Processing three times through the processing device achieved a PLI of greater than 60%, with the greatest increase in PLI occurring in the first pass through the device. Processing reduced particle-size, but 45% to 56% of the material dry mass was greater than 6 mm at the greatest processing level. Processing severely disrupted the mechanical structure of the stems, making them more compliant resulting in 26% to 56% greater compacted density than the chopped control. Processing reduced silage pH and increased fermentation acids compared to the chopped silage, indicating processing improved silage quality. Keywords: Alfalfa, Density, Haylage, Impact, Particle-size, Shredding.