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Many farms run livestock production along with a biogas plant. Priority is the effort to prepare high-quality feed and high-quality feedstock for the biogas plant. However, deciding which harvesting technique to choose seems a difficult task. In this study, the influence of harvest technique on silage quality and thus on the methane yield during anaerobic digestion was investigated. Maize was harvested for silage and shredlage production. Two-year results showed that the chemical composition of water leachate from silage and the total solids content did not indicate any significant differences between maize silage and shredlage. Methane yield in the first year ranged from 0.2735 ± 0.0095 m3/kgVS (maize silage) to 0.3024 ± 0.0090 m3/kgVS (shredlage) and in the second year from 0.3047 ± 0.0110 m3/kgVS (maize silage) to 0.3147 ± 0.0086 m3/kgVS (shredlage). Methane concentration in biogas did not show any significant differences for the two types of harvesting techniques in both years. The results showed that harvest technique had no additional effect on the methane content in biogas and thus on the methane yield.

In recent years, various substrates for increasing the production of biomethane are increasingly exploring. The effect of such substrates on methanogenesis is investigated mainly in small volume digesters. However, operating acetogenic biogas plants depending on substrates combinations and monitoring of microbial communities in the anaerobic digesters located in the Czech Republic have never been studied yet. The variation in the distribution of main acetogenic genera in eight biogas plants based on different input substrates ratio was studied. The genera composition was identified by sequencing of the 16S rRNA gene. In total, 33 genera of this group of microorganisms were found out. The highest percentage (30.2%) of acetogens compared to other biogas plants was observed in Modřice biogas plant with the input substrate biological sludge and primary sludge (50/50, w/w %). The smallest percentage (1.14%) and variation in the distribution of acetogenic microorganisms was found in Cejc biogas plant, with the input substrate maize silage and liquid pig manure (80/20, w/w %). For the biogas plant operator it would be important to know the composition of a consortium of anaerobic microorganisms that are present in anaerobic digesters (in two regions in the Czech Republic) processing different input combinations of a raw material. This paper characterizes the effect of the input raw materials on the variation in the distribution of the microbial community.

Objectives As a liquid organic fertilizer used in agriculture, digestate is rich in many nutrients (i.e. nitrogen, phosphorus, sulfur, calcium, potassium); their utilization may be however less efficient in soils poor in organic carbon (due to low carbon:nitrogen ratio). In order to solve the disadvantages, digestate enrichment with carbon-rich amendments biochar or humic acids (Humac) was tested. Methods Soil variants amended with enriched digestate: digestate + biochar, digestate + Humac, and digestate + combined biochar and humic acids—were compared to control with untreated digestate in their effect on total soil carbon and nitrogen, microbial biomass carbon, soil respiration and soil enzymatic activities in a pot experiment. Yield of the test crop lettuce was also determined for all variants. Results Soil respiration was the most significantly increased property, positively affected by digestate + Humac. Both digestate + biochar and digestate + Humac significantly increased microbial biomass carbon. Significant negative effect of digestate + biochar (compared to the control digestate) on particular enzyme activities was alleviated by the addition of humic acids. No significant differences among the tested variants were found in the above-ground and root plant biomass. Conclusions The tested organic supplements improved the digestate effect on some determined soil properties. We deduced from the results (carbon:nitrogen ratio, microbial biomass and activity) that the assimilation of nutrients by plants increased; however, the most desired positive effect on the yield of crop biomass was not demonstrated. We assume that the digestate enrichment with organic amendments may be more beneficial in a long time-scaled trial.