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.

A significant amount of waste is generated in the food industry, which is both an environmental and an economic problem. The recycling of this waste has become an important area of research. The processing of grapes produces 20–30% of the waste in the form of grape pomace and stalks. This article assesses the fuel values of these materials before and after torrefaction. The input materials were grape pomace samples from the varieties Riesling (Vitis vinifera “Welschriesling”) and Cabernet Sauvignon (Vitis vinifera “Cabernet Sauvignon”) from the South Moravia region and stalks from the variety Welschriesling. The torrefaction process was performed using a LECO TGA 701 thermogravimetric analyzer under nitrogen atmosphere at set temperatures of 225 °C, 250 °C, and 275 °C. The residence time was 30 min. Elemental analysis, calorific value, and gross calorific value were determined for all samples. The analyses show a positive effect of torrefaction on fuel properties in the samples. Between temperatures 250 °C and 275 °C, the carbon content increased by 4.29 wt.%, and the calorific value increased with the increase in temperature reaching a value of 25.84 MJ·kg⁻¹ at a peak temperature of 275 °C in the sample grape pomace from blue grapevine.

Every year, scaling plants buy (up to tens of tons) cones which needs to be peeled. After the process of scaling, the cones themselves are waste, which is partly sold. The problem of waste disposal is especially severe in plants where the processing is performed by electrically-powered scaling cabinets, but the problem does not apply to facilities where pellets are burned to produce beat. We examined the beat of combustion and calorific value of the residues from scaling plants that can be used in the production of refined wood fuels. The residues consist of the empty cones of pine, spruce, larch as well as husks and stems of silver fir. Additionally, we conducted measurements of the beat of combustion for wood and cones of each species and compared them to their respective calorific values. The results revealed that the average calorific value of the cones is in the range 17.81-19.86 MJ/kg. Our work showed that empty cones have a significantly higher calorific value and beat of combustion than the wood of spruce, larch and fir. In the case of pine, cones and wood did not differ significantly. These results led us to the conclusions that empty de-scaled cones can be utilised as a valuable primary solid fuel or fuel additive for the production of refined products for the local market. Due to the low annual production of cones in comparison to other materials such as sawdust and wood chips, pine cones should be used as a supplement, to enrich fuels of inferior quality by enhancing their energetic properties.

The use of grape residues as a renewable energy source for combustion presents various problems. One of these is the excessive production of carbon monoxide and nitrogen oxides. Analyses and combustion tests were performed on white and red grape pomace as well as grape stems. To verify the possibility of a reduction in emissions, straw of Miscanthus sinensis was added to mixtures with red grape pomace. Emission concentrations of carbon monoxide and nitrogen oxides were determined on a grate combustion device with a nominal thermal output of 8 kW under steady-state conditions. In addition to these emission concentrations, the excess air factor and the flue gas temperature were monitored. The results show a high energy content in grape residues. In red grape pomace, the gross calorific value of dry matter reached 22.17 MJ kg⁻¹. Unfavourable properties included high ash and nitrogen contents. During combustion tests on all types of grape residue, the emission concentrations of carbon monoxide were above the legal limit for the combustion of solid fuels. The addition of Miscanthus straw improved the behaviour during combustion. The maximum content of grape pomace in the mixture capable of meeting legislative emission requirements was 50% wt.