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Utilizing Forest Biomass by Adding a Small Chipper to a Tree-Length Southern Pine Harvesting Operation

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We investigated the addition of a small chipper (Conehead 565) to a mechanized, tree-length system to harvest tops, limbs, and understory (1–4 in. dbh) biomass. Three replicates of three treatments (A, tree-length only; B, tree-length with limbs and tops chipped; and C, tree-length with limbs, tops, and understory chipped) were evaluated in a 33-year-old slash pine plantation on a flatwoods site in the lower coastal plain of Echols County, Georgia. The site contained an estimated 7.7 green tons/ac of understory biomass with an average dbh of 2 in. Water oak, swamp bay, and red maple accounted for 73% of the stems. Roundwood production averaged 65.8 tons/ac and did not differ significantly across the three clearcut treatments. A vanload of chips was produced for every 18 and 5 truckloads of roundwood in Treatments B and C, respectively. There were significant differences in the weight per acre of chips produced between Treatment B (3.8 green tons/ac) and Treatment C (10.8 green tons/ac) at the α = 0.1 significance level but not at the 0.05 significance level. Total production averaged 28.6 tons per scheduled machine-hour and did not differ significantly across the three treatments. Green chips averaged 45% moisture content when produced, and laboratory results showed heat content values of 19.1 MJ/kg, which is comparable to other woody biomass. Nutrient removals from the site were relatively low, with losses associated with Treatment B comparable to annual atmospheric deposition. Raking costs associated with site preparation were significantly reduced (by $23/ac) on Treatment C, where the understory was also chipped. Both Treatment B and Treatment C had significantly less area lost to debris piles (1.0%) after site preparation than tree-length harvesting without chipping residuals (1.7%). Chipping logging residues along with understory stems in a clearcut harvest produced quality energy chips at a competitive cost, reduced site preparation cost, and increased plantable area.

Keywords: forest biomass; fuel chips; logging operation; nutrient loss; renewable energy

Document Type: Research Article

Publication date: 2007-11-01

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  • Each regional journal of applied forestry focuses on research, practice, and techniques targeted to foresters and allied professionals in specific regions of the United States and Canada. The Southern Journal of Applied Forestry covers an area from Virginia and Kentucky south to as far west as Oklahoma and east Texas.
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