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Effect of Mechanical Activation Frequency on the Reactivity of Phosphate Rock Mixtures in an Impact Mill
Ukraine’s biogas potential: a comprehensive assessment of energy yields and of feedstock availability
Energetic Potential of Tobacco Waste Within Combustion or Anaerobic Digestion
The growing demand for energy biomass encourages the use of waste and by-products from agriculture. The aim of this study was to assess the suitability of tobacco stalks (TSs) for energy use in the combustion and anaerobic digestion (AD) process, as well as the technical and environmental effects of energy production from this waste raw material. Laboratory tests were conducted on the energy parameters of TS biomass, the chemical composition of ash from its combustion, and the efficiency and composition of biogas generated during the AD process of TS silage with various silage additives. The tests were conducted in accordance with the standards applicable to biomass fuels. The energy yield and emission reduction obtained by the replacement of conventional energy sources were calculated. The energy parameters of TS were inferior compared to the raw materials most often burned in boilers (wood, straw). The high ash content (7.31% in dry mass) and its chemical composition may adversely affect heating devices. Methane yield from TS silage was lower (18.55–24.67 m3/Mg FM) than from silage from crops grown for biogas plants (i.e., 105 m3/Mg for maize silage). Silage additives improved TS silage quality and methane yield (from 18.55 to 21.71–24.67 m3 CH4/Mg in case of silages with additives. Energy yield and emission reduction were higher in the case of TS combustion, but AD is a process consistent with the circular economy. Both TS energy management processes are in line with the Sustainable Development Goals as they prevent the devaluation of agricultural waste, providing a valuable resource for bioenergy.
Food Waste Bioconversion Features Depending on the Regime of Anaerobic Digestion
Approximately one-third of global food production is wasted annually, which contributes significantly to greenhouse gas emissions and economic costs. Anaerobic digestion (AD) is an effective method for converting food waste into biogas, but its efficiency depends on factors such as temperature and substrate composition. This study compared mesophilic and thermophilic AD of selectively collected fruit and vegetable waste, quantifying process efficiency and identifying factors leading to collapse. Studies were performed in 1 dm3 reactors with gradually increasing organic loading rates until process collapse. Process dynamics, stability, and gas yields were assessed through daily biogas measurements and analyses of pH, FOS/TAC ratio, sCOD, ammonia, volatile fatty acids, alcohols, total and volatile solids, and C/N ratio. Research has shown that peak methane yields occurred at OLR = 0.5–1.0 kg VS·m−3·d−1, with thermophilic systems producing 0.63–5.48% more methane during stable phases. Collapse occurred at OLR = 3.0 in thermophilic and 4.0 in mesophilic reactors, accompanied by sharp increases in methanol, acetic acid, butyric acid, propionic acid, and FOS/TAC. The pH dropped to 5.49 and 6.09. While thermophilic conditions offered higher methane yields, they were more susceptible to rapid process destabilization due to intermediate metabolite accumulation.
Evaluation of Changes in the Chemical Composition of Grasses as a Result of the Methane Fermentation Process and Biogas Production Efficiency
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.
Integration of Plant Pomace into Extruded Products: Analysis of Process Conditions, Post-Production Waste Properties and Biogas Potential
Waste streams from cereal-based food production processes, rich in organic matter and carbohydrates, have untapped potential for biogas production. This study uniquely investigated the extrusion-cooking process conditions, physical properties and biogas efficiency of snack pellets enriched with plant pomace (apple, chokeberry, pumpkin, flaxseed and nigella seeds) at different levels (10, 20 and 30%), produced using a single-screw extruder-cooker. The highest efficiency obtained in the extrusion-cooking process (18.20 kg/h) was observed for pellets with the addition of 30% flaxseed pomace. The SME value during the entire process was in the range of 0.015–0.072 kWh/kg. New insights into the interaction between the inclusion of pomace, the physical properties of the extrudate and the anaerobic fermentation efficiency were obtained. The results show that 30% chokeberry extrudate maximized methane production (51.39% gas), demonstrating a double innovation: improving snack pellet quality and converting food waste into renewable energy.
Fuel Pelletization of Digestate: A Pathway to Renewable and Sustainable Energy Sources
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.
The efficiency of organic pollutants degradation in the process of anaerobic digestion of feedstocks with different origin
The study of the degree of degradation of pollutants in the process of anaerobic digestion and their content in digestate is an urgent scientific issue driven by the necessity to confirm the safety of using this product as a biofertilizer to improve the quality of agricultural land. The aim of the article was to determine the efficiency of the degradation of pollutants in the process of anaerobic digestion with the use of various additional treatment methods. A meta-analysis was conducted to establish the patterns of pollutant degradation during anaerobic digestion under different conditions and with the application of additional process intensification technologies (ultrasound, the use of chemical reagents and carbon cloth, interspecies electron transfer, immobilisation of microalgae, etc.). The reliability of the selected hypotheses and the statistical significance of the obtained data were determined using statistical analysis methods. It was found that additional treatment methods allow to increase in the efficiency of degradation of organic pollutants in mixed organic waste by 180% (direct interspecies electron transfer), in animal waste by 115% (alkaline pre-treatment), and in wastewater sludge by 55% (by treating them in a thermophilic aerobic reactor together with anaerobic digestion). The efficiency of the immobilisation of microalgae technology, which provides for the removal of pollutants from the liquid fraction of digestate, is 135%. The presence of a synergistic effect of additional methods of feedstock treatment has also been established, which is illustrated by an increase in the amount of methane production by 98.88-261.56%, depending on the type of waste and the treatment method. The results obtained prove the high efficiency of additional treatment technologies. The practical significance of the results obtained lies in the proven synergistic effect of using additional methods of treatment of feedstocks and digestate due to an increase in the level of degradation of organic pollutants with the production of environmentally safe fertilizer and an increase in biogas yield
The Effect of Corn Ensiling Methods on Digestibility and Biogas Yield
This study investigates the impact of different corn silage preparation methods, namely the traditional and Shredlage methods, on digestibility and biogas yield in anaerobic digestion and its nutritional value—the first complex study of its kind. Key parameters of both silage types were analyzed, including chemical composition, fiber content, and elemental makeup. Methane and biogas production were assessed under standardized fermentation conditions. The results showed that the Shredlage method, characterized by more intensive chopping, led to higher biogas and methane yields per unit of organic dry matter compared to traditional silage. This improvement is attributed to enhanced digestibility due to the lower content of neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude fiber in Shredlage. An elemental analysis revealed slight differences in carbon-to-nitrogen (C/N) ratios, with both silages showing values suitable for efficient fermentation. Despite minor variations in mineral content, Shredlage demonstrated greater efficiency in biogas production, particularly for rapid fermentation processes. The findings underscore the importance of silage preparation techniques in optimizing biogas yield and suggest Shredlage as a superior option for enhancing energy recovery in biogas plants. Future work should explore the economic trade-offs and scalability of these methods.