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/m3, apparent density 725 to 908 kg/m3, and specific density 1111 to 1350 kg/m3. The findings were compared to the results of previous research on other forms of forest biomass. The measured apparent-to-specific density conversion coefficient was β = 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.

Wood chips from logging residues are a renewable solid fuel that has become widely used in the energy sector. The current work presents a review of European papers on various aspects of wood chips production published in the years 2005–2018. The effects of the comminution method on the quality and energy parameters of the resulting wood chips were analysed. Most authors identified terrain and roadside chipping as the optimum technologies from the energy viewpoint. Furthermore, seasonal changes in the moisture content of wood chips have implications for their ash content and calorific value and determine the annual patterns of supplies to energy plants. In general, logging residues should be chipped approximately five to seven months after harvesting and delivered over economically feasible distances, which have increased in recent years due to the large dispersion of forest areas and energy plants. In a number of cases, logging residue chips did not meet the quality specifications contained in the relevant ISO standards, which may result in technological problems with their burning, especially in small to medium energy plants.

This paper presents the results of the analysis of the chemical composition and content of heavy metal contamination in forest logging residues, in order to assess the possibility for their further utilisation. The samples were divided into 9 groups, which included coniferous tree cones, wood, and other multi-species logging residues. The elementary composition, ash content, and calorific value were determined as energy use indicators for the samples. Additionally, the content of heavy and alkali metals, which may affect combustion processes and pollutant emissions, was tested. The high content of heavy metals may also disqualify these residues for other uses. The research shows that the test residues are suitable for energy use due to their high calorific value and low content of heavy metals. However, an increased ash content in some samples and the presence of alkali metals, causing high-temperature corrosion of boilers, may disqualify them as a potential fuel in the combustion process. The forest residues may be used in other thermal processes such as pyrolysis or gasification. A low content of heavy metals and a high content of organic matter permit the use of these residues for the production of adsorbents or composite materials.