Forest Residues as a Renewable Source of Energy: Elemental Composition and Physical Properties

Forest residues are a potentially important source of renewable energy. They are generated as a byproduct of timber harvesting around the world. To optimize the utilization of such biomass, one must know its physical and chemical properties. This paper presents an analysis of comminuted forest residues from Pinus sylvestris L. They were classified into four size fractions for which three density parameters were established pursuant to relevant standards. The mean bulk density of the fractions amounted to 110 to 190 kg/m(3 ), apparent density 725 to 908 kg/m(3 ), and specific density 1111 to 1350 kg/m(3 ). The findings were compared to the results of previous research on other forms of forest biomass. The measured apparent-tospecific density conversion coefficient was beta = 0.64. The elementary composition of forest residues measured in this work differed from that of other biomass types described in literature. In terms of carbon, nitrogen, sulfur, oxygen, and ash content, statistical analysis showed that the two compared types of biomass (forest residues and energy wood chips) formed two separate homogeneous groups, while both of these materials constituted one homogeneous group in the case of hydrogen content. The calorific value of the forest residues was 15.78 +/- 0.39 MJ/Kg.