• Energy Research

Analyses were conducted on 10 grass species from permanent grasslands in the Noteć Leniwa and Noteć Bystra valley. Their chemical composition was assayed, and their heat of combustion and heating value were determined. The cellulose content ranged from 33.38% to 38.68%, while the content of lignin ranged from 15.42% to 21.99%, and that of hemicellulose from 30.27% to 34.31%. The heating value of grasses was comparable to that of wood from 2- to 3-year-old willows and other fast-growing energy crops. However, the calorific value of naturally dried grasses may be slightly lower. The quantities of minerals in these grasses, exceeding those in wood, did not result in a lowering of their heat of combustion. The analyses clearly showed that the investigated grass species may be successfully used for energy generation purposes.

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 authors’ 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 needed—especially 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.