The costs for harvest, aggregation, storage, and transport of dry biomass are all impacted by bale density. Manufacturers are now offering high-density (HD) balers to meet demands to lower biomass feedstock costs. Field evaluation of HD balers was conducted to quantify achievable bale density and subsequent specific energy consumption (SEC) required to bale common biomass crops. Maximum bale densities were 180 and 240 (kg DM)·m~(-3), for wheat straw and switchgrass, respectively. Baling SEC increased as a second-order polynomial function of bale density. Although conventional plunger head balers can create HD bales, the balers are expensive and baling is power intensive, requiring large tractors. We propose an alternative approach where HD bales are created by reshaping and recompressing low-density square or round bales. Pressure-density relationships show that HD recompressed bales can be created with much lower energy requirements than by conventional methods. An alternative, novel approach to creating HD large-square bales by continuous compaction using an auger with compressing rollers was developed and field evaluated. With this technology, square (80 × 80 cm) wheat straw bales in excess of 180 (kg DM)·m~(-3) were produced with the auger baler which is much less complex and lighter weight than a conventional plunger head baler.
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