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.

• Klíčová slova
• biochar, biomass, calorific value, energy residual, nut shells, spent coffee ground, spruce wood, tea waste,
• Publikační typ
• časopisecké články MeSH

As a push towards alternative and renewable resources for heat and power generation, biomass and thermally treated fuels from biomass may be viable options in the upcoming economic reality. This study the verified mass and energy balance of spruce woody biomass after low temperature pyrolysis between 250 and 550 °C. The results showed that low-temperature pyrolysis can yield high-grade biochar suitable for substitution of fossil fuels. Crucially, the net calorific value of biochar processed at 350 °C substantially exceeded that of brown coal. An economic analysis was carried out on the assumption of the current economic reality in the Czech Republic. It was shown that even if the price of the biochar slightly increased, it would still be beneficial to invest in torrefaction technology over paying carbon credits.

• Klíčová slova
• biochar, economic analysis, renewable fuels, spruce, torrefaction,
• Publikační typ
• časopisecké články MeSH

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.

• Klíčová slova
• biochar, biofuel, biomass, calorific value, phytotoxicity, tea waste,
• Publikační typ
• časopisecké články MeSH