Short rotation coppices, grasses and other herbaceous crops: Biomass properties versus 26 genotypes and harvest time

Plant biomass is a highly diverse material whose properties depend on its origin, plant species and weather conditions. Since perennial plants biomass features are so diverse, their usability as feedstock for energy generation, for industry or for integrated biorefineries can vary. The literature provides only scarce data regarding a comparison, in the same soil and climate conditions, of the quality of biomass of various genotypes of perennial plants. Therefore, the aim of this study was to assess the thermophysical properties and elemental composition of 26 perennial plant genotypes (15 short rotation woody crops, 6 herbaceous plants and 5 grasses) obtained at three different dates (November, January, March) in three consecutive harvest cycles. The harvest date of short rotation woody crops did not have a significant effect on the moisture content in the harvested biomass, which was on a high, constant level. However, harvesting biomass of semi-woody (herbaceous) and straw (grasses) crops at a later date had a significant, beneficial effect on a decrease in the moisture content and increase the lower heating value. Short rotation woody crops biomass contained less ash and more carbon and hydrogen compared to herbaceous and grasses. Furthermore, the content of sulphur and ash in the biomass of semi-woody and straw crops decreased as the harvest date became later.