Energy balance of extensive wood chip production from short rotation coppice

Wood chips from short-rotation coppice (SRC) are an important source of lignocellulosic biomass, with a wide range of applications in integrated biorefineries for bioproducts and renewable energy materials. The aim of this study was to determine the energy inputs, energy gain, energy intensity, diesel fuel consumption and energy ratio of wood chip production from six SRC clones (three willows and three poplars) grown extensively at three planting densities, and harvested during an eight-year harvest cycle. The P1–Max-5 and S3–25 clones demonstrated the highest energy inputs (an average over 28 GJ ha –1 ), while the value of this indicator for the remaining four clones was 10–27% lower. The highest average energy gain (1390.2 GJ ha –1 ) was achieved by the willow clone S3–25, which was also characterized by the lowest energy intensity (0.33 GJ Mg –1 d.m.). The same clone yielded the highest energy ratio (an average of 49.79) at the SRC plantation. This was followed by the clones P2–H275, S2–Ekotur, P1–Max-5, P3–Andro and S1–Żubr, which had lower values by 6.4%, 14.3%, 16.5%, 27.0% and 34.3%, respectively, compared with S3–25. After considering the transport distance of SRC chips to the biomass conversion facility at distances of 25, 50, 100 and 200 km, a decrease in energy ratio by an average of 11%, 20%, 33% and 50%, respectively, was observed compared with the values obtained at the SRC plantation.