Energy feedstock characteristics of willow and hybrid poplar clones at harvest age

Woody biomass feedstock produced from willow and hybrid poplar can be converted into bioenergy via thermochemical and biochemical processes. Variation in key properties that relate to the quality of biomass feedstock and determine its value for energy conversion were determined at rotation age (3 years), in 30 willow and seven hybrid poplar clones, grown in a short-rotation intensive culture (SRIC) system in central NY. Substantial clonal variation in the concentrations of nitrogen (2.9–5.0 gkg−1), phosphorus (0.4–0.8 gkg−1) potassium (1.2–2.4 gkg−1), sodium (0.09–0.20 gkg−1), calcium (3.9–8.9 gkg−1), magnesium (0.2–0.6 gkg−1), ash (13.2–27.2 gkg−1) and bark percentage (3.6–8.1%) was found in stem (bark+wood) samples. A lower amount of variation was documented for specific gravity (0.33–0.48 gcm−3) and percent moisture (49–56%). Bark had a higher concentration of inorganic elements and ash, relative to wood. Willow clones as a group had a higher specific gravity, bark percentage and calcium concentration relative to hybrid poplar clones, which had a higher potassium concentration. The two groups were similar in terms of the concentrations of other elements and ash. Clonal variation in these characteristics present opportunities for manipulating feedstock quality through selection, breeding and plantation management.