Energy analysis of <italic>Eucalyptus grandis</italic> production in Hawaii: Fid-Bau Portal

Energy analysis of Eucalyptus grandis production in Hawaii

Turn, S. / Smith, L. / Koch, N. / Taniguchi, S.

An energy analysis was performed on the Eucalyptus grandis production system practiced in Hawaii with a system boundary defined as the edge of the plantation. Mass and energy flows crossing this boundary were inventoried over a seven year production rotation and unit factors were applied to convert mass and energy flows to a common energy basis, MJ per hectare. Based on a seven year harvest rotation, energy equivalents of production inputs totaled 46.5 GJ ha⁻¹. Energy used in harvesting, primarily diesel fuel, accounted for ∼70% of the total energy input to the system. Herbicide and nitrogen fertilizer contributed 16.9% and 7.1% of the total, respectively, and were the second and third largest input energy flow streams. E. grandis wood was the sole energy output from the system and averaged 290 GJ ha⁻¹ yr⁻¹ at the Hamakua plantation site. The total wood energy harvested from the system was estimated at 2.0 TJ ha⁻¹. The input and output energy flows were used to calculate energy ratios for lower altitude and higher altitude plantation sites of 43.7 and 40.8 units of wood energy produced per unit of fossil energy input, respectively. Methods that will be used to harvest plantation E. grandis in Hawaii are currently not well established. Equipment selection, machine productivity (ha harvested h⁻¹), and fuel consumption rates are important factors in the input energy total. Replacing assumptions with data from actual practice will reduce uncertainty and potentially improve energy ratio values.