Understanding Effects of Bioenergy Harvesting in Southern Forests
As a new wood-to-energy market develops, concerns exist in regard to the expanded removal of forest biomass. Biomass harvesting technology can recover and use many forms of woody material and some potential conversion processes can accept any organic material including shrubby and herbaceous biomass. A number of States have developed biomass removal guidelines specifying retention of a certain proportion of material and these are generally consensus recommendations, however, there is a lack of solid data from actual field operations. Forest Service researchers have examined the collection efficiency of biomass harvesting operations ranging from mulching and baling to whole-tree clearcutting.
The researchers tested mulch and bale machines in conditions as varied as pine plantation understory to juniper woodlands and less than 50 percent of potential understory shrub and herbaceous biomass was recovered in bales. Additional studies of whole-tree clearcutting revealed that of the total preharvest aboveground biomass of about 83 percent was recovered in clean chip volume and another 4 percent was recovered in biomass residues, leaving 13 percent (26 green tons per acre) onsite as nonrecoverable biomass. Researchers also collected destructive biomass samples to determine nutrient and carbon mass balance.
Harvesting operations are still limited by tree and equipment conditions, however, and full utilization is not technically feasible. This research documented actual biomass recovery in pine plantation clearcuts and found a 4-percent increase in removal volume. Further work will quantify nutrient losses.
Forest Service Partners