The paper presents an analysis of methods for utilizing digestate for energy purposes from two different biogas plants using different technologies. Biogas plant A used only cattle manure and corn silage as substrates, while biogas plant B used technology based on the utilization of food production waste. The analysis showed differences in the chemical, elemental, and thermogravimetric composition of both types of digestate. An analysis of the energy inputs required to produce fuel from digestate was also performed, along with energy balance calculations. The research and analysis led to the conclusion that both types of digestate are suitable for energy recovery. The possibilities of optimizing the process using excess heat from the biogas plant were also analyzed. In the case of digestate A, the combustion heat of digestate B was 17.20 MJ·kg−1, while for digestate A, it was 14.80 MJ·kg−1. The calorific value of digestate A at 8.79% moisture content was 13.40 MJ·kg−1, while for digestate B at 6.03% moisture content, it was 15.80 MJ·kg−1, respectively.
Herkowiak et al. (Mon,) studied this question.
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