HighlightsRotary knives were added to an ear-snapper header to increase corn stover yield in a single-pass biomass system.Stover yield increased with the number of knives but at the expense of combine productivity and fuel consumption.Bale moisture was often greater than would be considered appropriate for good aerobic conservation.Abstract.Modifications were made to a conventional ear-snapper corn header to increase corn stover yield when a single-pass round baling system was integrated with a combine harvester. To collect more leaves and top portions of stalks, knives oriented parallel to the deck plates were added to shear crop material above the ear-snapper rolls. Stover yield was primarily altered by the number of knives on the header; and to a lesser extent by the fore-and-aft position of the knives and the header height. The number of knives on a 12-row header was varied from two to six in increments of two. Stover yield increased linearly with the number of knives, and dry basis stover yield ranged from 1.1 Mg ha-1 (no knives) to 3.6 Mg ha-1 (six knives) over the five years of data collected (2012 to 2016). Combine productivity decreased linearly and specific fuel consumption increased linearly with greater stover yield. Combine productivity declined by as much as 50% when six knives were used. Dry basis bale density decreased linearly with the number of knives because the dense cobs became a smaller fraction of the total bale mass. In three of the five years, bale moisture increased linearly with the number of knives; in those three years, bale moisture was typically greater than 30% (wet basis). Adding knives to the header increased single-pass stover yield but at considerable cost to combine harvester productivity, and aerobic bale conservation would be challenged by high bale moisture. Keywords: Baling, Combine, Corn, Density, Moisture, Productivity, Stover, Yield.

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This research quantified the unit and bulk density of several biomass crops across a variety of harvest and processing methods, as well as the energy and fuel requirements for these operations. A load density of approximately 240 kg·m −3 is needed to reach the legal weight limit of most transporters. Of the three types of balers studied, only the high density (HD) large square baler achieved this target density. However, the specific energy and fuel requirements increased exponentially with bale density, and at the maximum densities for corn stover and switchgrass, the dry basis energy and fuel requirements ranged from 4.0 to 5.0 kW·h·Mg −1 and 1.2 to 1.4 L·Mg −1 , respectively. Throughputs of tub grinders when grinding bales was less than any other harvesting or processing methods investigated, so specific energy and fuel requirements were high and ranged from 13 to 32 kW·h·Mg −1 and 5.0 to 11.3 L·Mg −1 , respectively. Gross size-reduction by pre-cutting at baling increased bale density by less than 6% and increased baling energy requirements by 11% to 22%, but pre-cut bales increased the tub grinder throughput by 25% to 45% and reduced specific fuel consumption for grinding by 20% to 53%. Given the improvement in tub grinder operation, pre-cutting bales should be considered as a means to increase grinder throughput. Additional research is needed to determine the energy required to grind high density pre-cut bales at high throughputs so that better estimates of total energy required for a high density bale system can be made. An alternative bulk feedstock system was investigated that involved chopping moist biomass crops with a precision-cut forage harvester, compacting the bulk material in a silo bag, and then segmenting the densified material into modules optimized for efficient transport. The specific fuel use for chopping and then compacting biomass crops in the silo bag ranged from 1.6 to 3.0 L·Mg −1 and 0.5 to 1.3 L·Mg −1 , respectively. At the proposed moistures, the compacted density in the silo bags was sufficient to achieve weight-limited transport although there would be less dry matter (DM) shipped than with the high density dry bale system. Additional development work is needed to create transportable modules from the compacted silo bag. The overall results of this research will allow more accurate estimates of biomass logistics costs based on product density and energy expenditures.

Abstract.When greater density bales are made, baler manufacturers recommend using twine with greater knot strength. When twine fails, bale integrity is lost, harvesting costs increase, and productivity suffers. Twine failure typically occurs in the knot on the top strand of the twine. A better understanding of twine tension in the top strands could help reduce failures, allow for improved knot strength recommendations, and ultimately lower baling costs. A system was developed to measure the tension of the top strands while baling a variety of crops with a high-density large square baler. Depending on the bale chute design, twine tension was greatest as the bale cantilevered from the chamber but had not yet touched the chute or just as the bale fully exited the bale chamber. In either case, the absolute maximum recorded tensions were typically less than 60% of the twine specified knot strength. Pulses in synchronization with the plunger frequency were superimposed on the nominal twine tension. Tension was usually greatest in the outer left twine and the other right twine because for each, there was only one neighboring twine to share the load. Average twine tension over the first 60 s after the bale rested on the ground was linearly related to bale density. Crop stress relaxation reduced tension up to 20% within 20 min after the bale was placed on the ground. Top strand tension approached 60% of knot strength for only a short duration as the bale exited the chamber and after that, the tension was much less than the specified knot strength. Therefore, design changes or strategies that reduce tension during the critical period when the bale exits the chamber could reduce maximum knot strength requirements and lead to lower baling costs. Keywords: Bales, Density, Tension, Twine.

Size-reduction of small grain residue is required on the combine harvester to promote uniform distribution of residue across the full harvested width. However, unnecessary size reduction increases energy expenditures that can reduce harvester capacity. To objectively quantify the degree of residue processing, an apparatus and method was developed for evaluating particle-size distribution of small grain crop residue. The apparatus consisted of a pre-screener to sort long particles and an oscillating cascade of three screens which separated material into four additional fractions. The separation process was continuous, so large volume samples could be separated more quickly than batch systems. The developed system was used to evaluate wheat residue which was processed to various extents by a combine residue chopper in two experiments. Statistically significant (p < 0.05) differences between variably processed wheat residues were found using the developed apparatus and methodology. The separated wheat residue was partitioned into three particle-size ranges of less than 50 mm, 50 to 125 mm, and greater than 125 mm. Samples of 3 to 4 kg could be completely analyzed in less than 10 min.