Sonne, Hall Edie (Univ. of Washington, College of Forest Resource, Seattle, WA, 98195; Phone: 206-329-3569; Email: edie@u.washington.edu)

Greenhouse Gas Emissions from Pacific Northwest Douglas-fir Forestry
Operations

E. Sonne Hall *

Most forest carbon assessments focus only on biomass carbon and assume that greenhouse gas (GHG) emissions from forestry activities are minimal. This study took an in depth look at the direct and indirect emissions from PNW Douglas-fir plantation forestry activities in order to support or deny this claim. GHG budgets for 408 “management regimes” were calculated using Life Cycle Assessment methodology. These management regimes were comprised of different combinations of three types of seedlings (P+1, 1+1, and large plug), two types of site preparation (pile and burn and chemical), transportation of seedling to field, 17 combinations of management intensity including fertilization, herbicide treatment, pre-commercial thinning (PCT), commercial thinning (CT), and nothing, and four different rotation ages (30, 40, 50, and 60 years). Normalized to 50 years, average direct GHG emissions were 3.68 metric tons CO₂e/acre, which accounted for 82 percent of total GHG emissions from the average of 408 management regimes. Harvesting (PCT, CT, and Clear Cutting) contributed the most to total GHG emissions (1.8 tons CO₂e/7500 cubic feet harvested timber), followed by pile and burn site preparation (0.8 tons CO₂e/acre or 26 percent of total GHG emissions) and then fertilization (0.56 tons CO₂e/acre or 18 percent of total GHG emissions). Seedling production contributed less than one percent of total GHG emissions when assessed per acre of planted timberland. Similarly, transportation of seedlings to field, chemical site preparation, and herbicide treatment each contributed about one percent to total GHG emissions. Emissions factors for each of the unit processes are presented separately and combined. The relative contribution of direct and indirect emissions was examined to see whether standard accounting procedures are acceptable. Finally, the relative contribution of each forest management decision is discussed and opportunities for reduction are identified. This paper will be followed with a second paper focused on changes in biomass carbon from different management alternatives, and putting biomass carbon and GHG emissions together to look at the total GHG budget from forestry activities.