Abstract
Willow biomass is used as a bioenergy source in various conversion technologies. It is noteworthy that apart from the beneficial environmental impact of a willow plantation, the biomass quality is also very important as it has an impact on the effectiveness of its use and emissions produced in various bioenergy technologies. Therefore, this study analysed the thermophysical properties and elemental composition of 15 genotypes of willow biomass from two plantations situated in the north of Poland, harvested in two consecutive three-year rotations. The differences in the moisture content, ash content and the lower heating value were mainly determined by the genotype, i.e., by genetic factors. In contrast, the content of carbon, nitrogen, sulphur and hydrogen was determined by the location (environmental factors), but also by the genotype, and by a combination of these factors. The following were the mean levels of the willow biomass characteristics, regardless of the location, genotype and harvest rotation: 48.9% moisture content, 1.26% d.m. ash content, 19.4% d.m. fixed carbon, 79.4% d.m. volatile matter, 19.53 MJ kg−1 d.m. higher heating value, 8.20 MJ kg−1 lower heating value, 52.90% d.m. carbon, 6.23% d.m. hydrogen, 0.032% d.m. sulphur, 0.42% d.m. nitrogen. The present research has shown that the selection of the willow genotype is important for the quality of biomass as energy feedstock. However, plantation location, as well as successive harvest rotations, can have a significant impact on the biomass elemental composition.
Highlights
Due to increasing levels of CO2 in the atmosphere resulting from anthropogenic activities, and many European Union (EU) countries striving to increase their energy independence, there is growing interest in the use of renewable energy sources (RES), which are successfully replacing fossil fuels [1,2,3,4,5]
The thermophysical characteristics of willow biomass were differentiated by the site and genotype and the majority of them by the harvest rotation and by the interactions of these factors (Table 1)
The lowest mean moisture content was determined in the biomass of the Sprint cultivar (S. viminalis) and the highest was in the biomass of the UWM 155 clone (S. dasyclados)
Summary
Due to increasing levels of CO2 in the atmosphere resulting from anthropogenic activities, and many European Union (EU) countries striving to increase their energy independence, there is growing interest in the use of renewable energy sources (RES), which are successfully replacing fossil fuels [1,2,3,4,5]. Bioenergy, especially solid biomass, is of the greatest importance. Bioenergy plays a important role in Poland, as it accounted for nearly 85% of energy production from RES in 2018, with solid biofuels accounting for over 69% [7]. Due to a large forest area in Poland 30% of the country area) and the amount of wood acquired annually (over 40 million m3 ) [8], wood processing industry waste and post-felling biomass, i.e., branches and twigs left over after tree felling, is the dominating source of woody biomass. The area of poplar and willow cultivation in the SRC system in Poland is estimated at approx. The area of poplar and willow cultivation in the SRC system in Poland is estimated at approx. 16.8 thousand ha [14]
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