The practice and economics of hybrid poplar biomass production for biofuels and bioproducts in the Pacific Northwest

Hybrid poplar demonstration-scale farms were managed in Oregon, Washington, Idaho, and California to establish management practices, yields, harvesting methods, and the economics of biomass production. Yield during the 2-year establishment cycle averaged 3.5 dry Mg ha⁻¹ year⁻¹ increasing to 11.6 Mg ha⁻¹ year⁻¹ in the ensuing 3-year coppice cycle. Populus deltoides (Bartram ex Marsh.) × P. maximowiczii (Henry) varieties preformed best in Oregon during the coppice cycle with the best variety producing 18.1 Mg ha⁻¹ year⁻¹, while P. ×generosa (Henry) varieties maximized yields in Washington at 22.1 Mg ha⁻¹ year⁻¹. P. ×canadensis (Moench) varieties excelled in Idaho and California with upper yields of 13.6 Mg ha⁻¹ year⁻¹ and 12.9 Mg ha⁻¹ year⁻¹, respectively. Stands were cut with a single-pass harvester 2 years after planting and a second time after 3 years of coppice growth; material capacity, limited by poor ground conditions, varied between 21.7 to 31.3 green Mg h⁻¹. Chemical composition averaged 1.87% inorganics, 7.74% extractives, 26.90% lignin, 38.07% glucan, 13.66% xylan, 1.61% galactan, 1.14% arabinan, and 2.76% mannan. Production costs (USD) projected over a 20-year rotation of six coppice cycles were $71.81 Mg⁻¹ in Washington, $89.91 Mg⁻¹ in Oregon, $98.76 Mg⁻¹ in Idaho, and $179.07 Mg⁻¹ in California. Land rental, establishment, crop care, harvest, transportation, and land restoration, respectively, accounted for 23%, 5%, 19%, 30%, 17%, and 6% of total feedstock cost. Farms were successfully restored to conditions existing before poplar conversion. In the absence of fertilization, increases in soil pH and decreases in nitrate-nitrogen, zinc, iron, and organic matter were consistently noted but could not be associated with poplar production alone.