Compression Characteristics of Selected Ground Agricultural Biomass
Agricultural biomass such as barley, canola, oat and wheat straw has the potential to be used as feedstock for bioenergy. However, the low bulk density straw must be processed and densified in order to facilitate handling, storage and transportation. It is important to understand the fundamental mechanism of the biomass compression process, which is required in the design of energy efficient compaction equipment to mitigate the cost of pre-processing and transportation of the product. Therefore, a comprehensive review of various compression models was performed and the compression behavior of selected ground agricultural biomass was studied. Five compression models were considered to determine the pressure-volume and pressure-density relationship to analyze the compression characteristics of biomass samples, namely: Jones (1960), Heckle (1961), Cooper-Eaton (1962), Kawakita-Ludde (1971) and Panelli-Filho (2001) models. Densification studies were conducted on four selected biomass samples at 10 % moisture content (w.b.) and 1.98 mm grind size using four pressure levels of 31.6, 63.2, 94.7 and 138.9 MPa. The mean densities of barley, canola, oat and wheat straw increased from 907 to 977 kg/m3, 823 to 1003 kg/m3, 849 to 1011 kg/m3 and 813 to 924 kg/m3, respectively. The Kawakita-Ludde model provided an excellent fit having R2 values of 0.99 for selected agricultural straw samples. It was also concluded that the ground oat and canola straw had the highest level of porosity and failure stress, respectively. The parameters of Cooper-Eaton model indicated that the ground straw samples were densified easily by the particles rearrangement method and Jones model indicated that canola and oat straw were more compressible as compared to barley and wheat straw.