Energy Valorization of Digestate from Biogas Plants: Development of Composite Fuel Pellets for Decentralized Combustion Systems

In light of the current energy and gas crisis, biogas from biogas plants is becoming increasingly in demand as a source of energy.The current trend of a significant increase in the number of biogas plants, especially in Europe, also brings with it a significant increase in the unused energy potential of the waste product -digestate, which in most cases is used only as fertilizer, which, however, also brings an adverse impact with increasing nitrogen in the soil.The aim of the presented research is to reassess the potential of using digestate from biogas plants in combination with spruce sawdust for the production of highquality composite pellets as a sustainable biofuel.The research focuses on the physical and mechanical properties of fuel pellets, which are produced with different weight ratios of digestate and wood component.Experiments show that the bulk density of pellets increases with increasing digestate content.However, the mechanical durability of pellets increases with increasing wood content.Special emphasis is placed on the analysis of chemicalthermal parameters, such as net calorific value and ash content, which are key parameters for assessing the environmental impact and energy efficiency of these biofuels.The results indicate that optimizing the pellet composition can contribute to improving the quality and sustainability of these energy applications.These findings provide valuable information for the future development of energy systems using biofuels from digestate and spruce sawdust.