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Waste as substrates for agricultural biogas plants: A case study from Poland
Energy production from renewable sources is one of the main ways to fight against global warming. Anaerobic digestion process can be used to produce biogas containing methane. In the light of the growing demand for substrates, a variety of raw materials are required. These substrates should be suitable for anaerobic digestion, and processing them need to provide the desired amount of energy. This paper aims to discuss the agricultural biogas market in Poland, its current state, and the possibility of development during energy transformation, in particular in terms of using waste as a substrate for energy production. In February 2022, there were 130 agricultural biogas plants registered in Poland. On the other hand, in 2020, 4,409,054.898 Mg of raw materials were used to produce agricultural biogas in Poland. Among all the substrates used, waste played a special role. With the right amount of raw materials and proper management of a biogas plant, it is possible to produce electricity and provide stable and predictable heat supply. Bearing in mind the development of the Polish and European biogas markets, attention should be paid to ensure access to raw materials from which chemical energy in the form of biogas can be generated. Due to limited access to farmland and the increasing demand for food production, one should expect that waste will be increasingly often used for biogas production, especially that with high energy potential, such as waste related to animal production and the meat industry.
Biogas Plant Operation: Digestate as the Valuable Product
Fertilization is an essential element in plant cultivation. Supplying the right amounts of nutrients allows plants to grow and develop. Due to the rising price of mineral fertilizers, other fertilizers and soil conditioners are growing in importance. One of these is the digestate produced in agricultural biogas plants. Due to its properties, the digestate can be used directly as a fertilizer. In this case, the effects of application can both change the soil environment and directly affect plant growth. Physical, biological, and thermal transformations can also produce products based on the digestate or its fractions, which can be successfully used for fertilizer purposes. Among other things, this paper discusses the production and use of composts, biocarbon, and/or fertilizer granules from the solid fraction of the digestate. Numerous scientific studies, including the authorsâ own research in this article, indicate that digestate can be successfully used as fertilizer, both without processing and with selected methods of treatment. However, further research is neededâespecially on the diversity of raw materials used for biogas production and their effects on the composition and performance of the digestate. In addition, research should continue on the processing of digestate into specific products, depending on the needs of soils and plants.
Ruderal Habitats: A Source for Biomass and Biogas
The aim of the study was to evaluate the chemical composition and biogas potential of selected ruderal and expansive plant species: Heracleum sosnowskyi, Aegopodium podagraria, Chaerophyllum bulbosum, Acer negundo, and Urtica dioica. Plant material was collected from a 19th-century park in the village of Niegolewo (Greater Poland Voivodship) and analyzed for cellulose, lignin, hemicellulose, extractives, and ash content before and after methane fermentation. Fermentation followed DIN 38 414-S8, and chemical analyses used standardized methods (TAPPI, Seifert, and DIN). Statistical analyses included ANOVA, CVA, and hierarchical clustering. The highest biogas yield was obtained from A. podagraria, which is associated with low lignin and high hemicellulose degradation. The results confirm the potential of ruderal biomass as a diverse source for biogas production.