Spent coffee ground is a massively produced coffee industry waste product whose reusage is beneficial. Proximate and ultimate and stochiometric analysis of torrefied spent coffee ground were performed and results were analyzed and compared with other research and materials. Spent coffee ground is a material with high content of carbon (above 50%) and therefore high calorific value (above 20 MJ·kg⁻¹). Torrefaction improves the properties of the material, raising its calorific value up to 32 MJ·kg⁻¹. Next, the phytotoxicity of the aqueous extract was tested using the cress test. The non-torrefied sample and the sample treated at 250 °C were the most toxic. The sample treated at 250 °C adversely affected the germination of the cress seeds due to residual caffeine, tannins and sulfur release. The sample treated at 350 °C performed best of all the tested samples. The sample treated at 350 °C can be applied to the soil as the germination index was higher than 50% and can be used as an alternative fuel with net calorific value comparable to fossil fuels.

Tea waste as a potential biofuel and bio fertilizer was analyzed. Samples were collected from various tea species and torrefied to five different temperatures. All samples were analyzed for their proximal composition and calorific value. From the results, stoichiometric properties were calculated. A phytotoxicity test was performed, and the germination index was measured. Tea waste torrefied at 350 °C may be suitable biofuel reaching the calorific value of 25–27 MJ kg⁻¹, but with quite a high share of ash, up to 10%, which makes its use technically challenging and may lead to operating issues in a combustion chamber. The same biochar may be a suitable fertilizer for increasing the germination index, therefore, applicable to the soil. The non-torrefied sample and the sample treated at 250 °C are not suitable as fertilizers for being toxic. The total phenolic content in waste black tea was reduced from 41.26 to 0.21 mg g⁻¹, depending on the torrefaction temperature. The total flavonoid content was also reduced from 60.49 to 0.5 mg g⁻¹. The total antioxidant activity in the non-torrefied sample was 144 mg g⁻¹, and after torrefaction at 550 °C, it was 0.82 mg g⁻¹. The results showed that black tea waste residues have the potential for further use, for example, in agriculture as a soil amendment or as a potential biofuel.

Walnut, pistachio, and peanut nutshells were treated by pyrolysis to biochar and analyzed for their possible usage as fuels or soil fertilizers. All the samples were pyrolyzed to five different temperatures, i.e., 250 °C, 300 °C, 350 °C, 450 °C, and 550 °C. Proximate and elemental analyses were carried out for all the samples, as well as calorific value and stoichiometric analysis. For sample usage as a soil amendment, phytotoxicity testing was performed and the content of phenolics, flavonoids, tannin, juglone, and antioxidant activity were determined. To characterize the chemical composition of walnut, pistachio, and peanut shells, lignin, cellulose, holocellulose, hemicellulose, and extractives were determined. As a result, it was found that walnut shells and pistachio shells are best pyrolyzed at the temperature of 300 °C and peanut shells at the temperature of 550 °C for their use as alternative fuels. The highest measured net calorific value was in pistachio shells, which were biochar pyrolyzed at 550 °C, of 31.35 MJ kg⁻¹. On the other hand, walnut biochar pyrolyzed at 550 °C had the highest ash share of 10.12% wt. For their use as soil fertilizers, peanut shells were the most suitable when pyrolyzed at 300 °C, walnut shells at 300 and 350 °C, and pistachio shells at 350 °C.

Biomass is a potential biofuel which may help fighting high carbon dioxide emissions and negative impacts of global warming. Analysis of Norway spruce ( Picea abies ) and barley ( Hordeum vulgare ) were performed at the laboratory of Czech University of Life Sciences. Material was torrefied in an inert nitrogen atmosphere at the temperatures of 250 °C and 280 °C for 45 minutes. Elementary and stoichiometric parameters were monitored and impact of torrefaction and pellet production on carbon footprint was determined. Torrefied and pelleted material showed better fuel properties in comparison to the original material. Calorific value of the torrefied spruce wood chip increased by 12.27% when torrefied at the temperature of 250 °C, and by 25.41% when torrefied at the temperature of 280 °C.

This study investigates the potential use of biochar derived from residues—such as spruce wood, spent coffee grounds, tea waste, and nutshells—as a sustainable coal substitute—to enhance the decarbonization of European energetic systems and decrease the dependence on fossil fuels. The biomasses were pyrolyzed at 250–550 °C, analyzed for calorific value and composition, and evaluated for energy retention and mass loss. The results show significant energy density improvements, with optimal temperatures varying by material (e.g., spruce wood reached 31.56 MJ·kg⁻¹ at 550 °C, retaining 21.84% of its mass; spent coffee grounds peaked at 31.26 MJ·kg⁻¹ at 350 °C, retaining 37.53%). Economic analysis confirmed pyrolyzed biomass as a cost-effective alternative to coal, especially considering emission allowance costs. Integrating biomass pyrolysis into regional energy systems supports decarbonization, reduces emissions, and advances us towards a circular economy.

The paper is focused on steel surface processing to ensure an improved adhesion of applied powder layer. Mechanical pre-treatment, chemical pre-treatment and their combination were used to compare their results with each other and to find out the pre-treatment that affected the final outcome the most. The final score was determined by the grid method. The outcome displayed a huge mutual dependency between the result and a kind of various surface treatments. The method with no pre-treatment was by far the worst, followed by the mechanical pre-treatment only, followed by the chemical pre-treatment only, and finally by their combination. The time of blasting affects the final outcome. Through the grid method, coating thickness, and aesthetic test it was confirmed that an optimal blasting time of 5 min provides the best outcome.