Milling of lignocellulosic biomass

Ethanol is being considered as an attractive alternative transportation fuel for the future. One method of producing ethanol from lignocellulose involves reducing the size of biomass to smaller particles, and using acid or enzyme treatments to hydrolyze the biomass to sugars. The size-reduction step is necessary to eliminate mass- and heat-transfer limitations during the hydrolysis reactions. However, milling to small size consumes large amounts of energy, and reducing the energy usage is critical to the overall process economics. In this study, the energy requirements and size distribution for milling wood were measured for various pilot-scale size-reduction equipment. Hammer milling used less energy than disk milling, but produced particles with a larger-size distribution. Additionally, energy requirements were measured for shredding paper and switchgrass.