2024, Waliszewska, Bogusława, Waliszewska, Hanna, Grzelak, Mieczysław, Majchrzak, Leszek, Gaweł, Eliza, Murawski, Maciej Krzysztof, Sieradzka, Agnieszka, Vaskina, Iryna, Spek-Dźwigała, Agnieszka

Methane fermentation, which is one of the key processes in biogas production, plays an important role in the conversion of biomass to energy. During this process, changes occur in the chemical composition of organic feedstocks, including the chemical composition of grasses. The assessment of these changes is crucial for the efficiency and productivity of biogas production. The material for this study comprised fully mature grass blades with leaves and inflorescences and was collected from extensively used meadows and pastures, as well as cultivated and set-aside areas in the Wielkopolskie Voivodeship, the communes of Białośliwie and Trzcianka, Poland. The aim of this study was to compare methane fermentation efficiency in nine grass species and identify the biomass component involved in biogas production. The results indicate that the fermentation process, as expected, changed the cellulose content. The lignin content of the grasses before fermentation varied more than the cellulose content. The content of holocellulose (sum of carbohydrate components) in the grasses ranged from 59.77 to 72.93% before fermentation. Methane fermentation significantly reduced the carbohydrate content in the grasses, with a low degree of polymerization. Grassland biomass-based biogas production is a viable alternative to conventional fossil fuels.

2025, Vaskina, Iryna, Vaskin, Roman, Ostroha, Ruslan, Yukhymenko, Mykola, Skydanenko, Maksym, Kupryaniuk, Karol, Demkova, Lenka, Sydorenko, Serhii

Digestate as a by-product of biogas production requires appropriate utilization methods to convert it into a valuable resource. This study investigated the feasibility of using digestate from a biogas plant as a sustainable feedstock for fuel pellet production. Digestate from an agricultural biogas plant was dried and pelletized, both with and without the addition of biochar. The resulting pellets were analyzed for their physicochemical properties, elemental composition, and calorific value. Samples of pellets were examined using a calorimeter and XRF analyzer. Results showed that digestate pellets exhibited promising fuel characteristics comparable to traditional wood pellets (17.07–17.11 MJ/kg). However, the addition of biochar, while increasing calorific value, led to high ash content and elevated concentrations of Cl, S, N, Ni, Zn, exceeding acceptable limits defined by ISO 17225-6. Consequently, biochar addition is not recommended due to potential environmental concerns upon combustion. The findings highlight that digestate with initial moisture content of 7–7.5% is the most suitable for pelletization in terms of mechanical durability and strength quality. Further research is recommended to fully assess the environmental and economic viability of digestate-based fuel pellets. This approach addresses two issues: it enables waste utilization and produces a valuable resource.