Evaluation of integrated harvesting systems in pine stands of the southern United States

We investigated the addition of a small chipper to mechanized, tree-length harvesting systems to produce biomass chips from tops, limbs, and underbrush in planted southern pine stands. The systems were examined in three replicated studies involving clearcuts and thinnings in 2006 and 2007 in the US state of Georgia. Biomass from understory stems ranged from 8.3 to 59.0 green tonnes per hectare in the three studies. Chipping the limbs and tops of merchantable stems did not reduce the production of roundwood, but only produced 7–11 t ha−1 of biomass. Harvesting understory biomass in addition to chipping limbs and tops worked well with clearcut harvests, but reduced roundwood production by 50% in thinnings. Small chippers added to roundwood operations appear to have limited potential in current market conditions, but should become a viable option as stronger markets for biomass chips develop.