Power requirement and energy consumption of bale compression

Bales of corn stover, indiangrass, switchgrass, and wheat straw were compressed to determine their compression behavior in baled form. On average, the volume of all bales that were compressed was reduced by 67.4%. The baled crops follow a nonlinear density vs. pressure relationship that can be accurately predicted using an exponential equation. As loading speed increased, the energy, power, and specific energy required to compress the baled herbaceous biomass crops also increased. However, since each crop behaved differently during compression, the speed interaction was dependent on type of crop. To achieve a 60% reduction in bale volume at the slowest compression speed (2.54 mm/s), switchgrass required 15.6%, 61.7%, and 55.4% more energy than indiangrass, corn stover, and wheat straw, respectively. There were no significant differences in power or specific energy required at the slowest speed (α = 0.05). At the fastest compression speed (106.7 mm/s), switchgrass required 32.4%, 59.4%, and 73.0% more energy, 12.9%, 20.5%, and 27.0% more power, and 11.1%, 6.1%, and 19.3% more specific energy than indiangrass, corn stover, and wheat straw, respectively.