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Reshaping and Recompressing Round Biomass Bales

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 59(4): 795-802. (doi: 10.13031/trans.59.11778) @2016
Authors:   Nolan C. Lacy, Kevin J. Shinners
Keywords:   Bales, Biomass, Compression, Density.

Abstract. Recompressing bales to achieve greater density can reduce biomass storage and transportation costs, but researchon recompressing round biomass bales is limited. Bi-axial compression in the radial direction of wheat straw, cornstover, switchgrass, and reed canarygrass was used to reshape round bales into a rectangular cross-section. The processwas conducted as a three-stage progression: vertical reshaping to cuboid shape, followed by vertical and then horizontaldensification. Density increased by 13% to 23% during vertical densification, and the pressure-density relationship wasmodeled as a linear function. Linear, power, and exponential models were fit to the pressure-density data collected duringhorizontal compression, during which density increased by an additional 68% to 83%. The linear and power functions bestmodeled the horizontal compression data. Although the power model underpredicted the initial density, it closely predictedthe final bale density, so this model would have greater utility for future design applications. The target density of 240 kgDM m-3 was achieved at the end of compression with all four crops. Corn stover had significantly greater final density thanthe other three crops and achieved the target density with less applied pressure. Bales were restrained with polyester strappingprior to removal from the chamber. Bale density decreased 19% to 30% due to re-expansion after pressure was released.Although the forces applied were great, the specific energy requirements were low because compression took placeover a relatively long time (~30 s). Differences in specific energy between crops were not statistically significant. Reshapingand recompressing large round bales could be an alternative to high-density large square baling to achieve weight-limitedtransport of baled biomass.

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