Forest biomass recovery by adding small chippers to tree-length harvesting systems in planted pine stands of the southern USA
Westbrook, Michael D.
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We investigated the addition of a small chipper (Conehead 565 or Woodsman 334) to mechanized, tree-length systems in planted southern pine stands to harvest tops, limbs, and understory (dbh 1-4 inch) biomass in addition to traditional roundwood products. The systems were examined in three replicated studies involving clearcuts and thinnings in 2006 - 2007 in Georgia. Understory standing biomass (excluding the limbs and tops of merchantable stems) ranged from 3.7 to 26.3 tons per acre in the three studies. Chipping the limbs and tops of merchantable stems did not reduce the production of roundwood, but only produced 3-4 tons per acre of biomass. Harvesting understory biomass in addition to chipping limbs and tops worked well with clearcut harvests, but reduced roundwood production by 50% in the thinning study. Small chippers added to roundwood operations appear to have the most potential in clearcut harvests where less than 15 tons per acre of biomass are harvested and daily chip production is approximately 70-80 tons per day (2-3 truckloads). Green chips averaged 45% moisture content while dry chips had higher heating values of 8200 BTU/lb, which is comparable to other woody biomass.