In-wood screening of wood grindings for biomass feedstock applications
Dukes, Charles Cory
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Logging residues present a substantial near term opportunity as a bioenergy feedstock, but contaminants can be introduced during collection. We studied the use of a trommel screen to reduce ash levels in ground forest harvest residues at time of production. Treatments of initial harvest type, grinder size, debris age, and screen usage were applied to southern pine residues in the coastal plain of South Carolina. After screening, the average ash levels of roundwood and clean chipped residues were reduced from 4.0% to 1.4% and from 11.9% to 6%, respectively. Average energy density was improved with screening, but not significantly. Large grinder utilization with roundwood residues was reduced when screening. Screened roundwood residues were consistently more costly to produce than unscreened roundwood or screened clean chipped debris with either grinder size. Financially, the screened clean chip systems and the unscreened roundwood material provided the most competitive residue on an energy basis.