The effect of mechanical pre-treatment of nine different agricultural substrates minced to particle sizes of 1.5 mm, 5 mm and 10 mm on biogas and methane yields and fermentation kinetics was investigated. The results showed, that for five of the nine tested substrates (grass, Progas rye, Palazzo rye, tall wheatgrass, beet), a higher biogas production was obtained for the degree of fragmentation of 10 mm compared to fragmentation of 5 mm and 1.5 mm. For fragmentation of 5 mm, the highest biogas production was achieved for sorghum silage, Atletico maize and Cannavaro maize—649.80, 735.59 and 671.83 Nm³/Mg VS, respectively. However, for the degree of fragmentation of 1.5 mm, the highest biogas production (510.43 Nm³/Mg volatile solid (VS)) was obtained with Topinambur silage. The modified Gompertz model fitted well the kinetics of anaerobic digestion of substrates and show a significant dependence of the model parameters H_max (biogas production potential) and R_max (maximum rate of biogas production) on the degree of substrate fragmentation.

The research concerned the elaborate of non-waste biogas production technology based on the development of digestate from anaerobic digestion. In the anaerobic digestion process, the substrates of plant origin in the form of silage were used. The digestate obtained after biogas production was processed using the ORTWED method into a valuable granulated organic-mineral fertilizer, which contains a solid fraction of digestate, calcium and biogenic elements. This method can be successfully applied in agriculture in the context of its sustainable development due to the growing problem of utilization of digestate forming in agricultural biogas plants.

This study was carried out to estimate the relevance of biological supplementation in improving the economic efficiency of anaerobic digestion (AD). Three kinds of silages—maize, grass, and igniscum—were initially inoculated with digestate and then supplemented with one of four vaccines containing different bacteria species (APD^®, PPT^®, JENOR^®) or a yeast and mold mixture (HAP^®). In addition, each plant silage was fermented without any additives (control A—maize silage, B—grass silage, and C—igniscum silage). The biodegradability process was performed in batch tests at a mesophilic temperature (38 °C). To compare the energetic efficiency of AD, the process kinetics, biogas, and methane production were analyzed. We found that the applied supplementation measures improved biogas production in the case of maize and igniscum (7–62% higher than controls), but decreased the yield of AD when grass silage was fermented (2–34% lower than controls). The greatest increase in methane production (by 79%) was observed when maize silage was digested with the PPT^® pretreatment, with 427 Nm³∙Mg⁻¹ VS (volatile solids).

The paper presents research on the impact of adding various forms of sorghum to sewage sludge on the anaerobic digestion process. The use of liquid sewage sludge alone in biogas plants at wastewater treatment plants is inefficient due to the low total solid (dry matter) content of this substrate. The tests revealed that the production of methane in biogas is low and amounted to 17.9% (105.4 Nm³∙Mg⁻¹, VS—volatile solid). Therefore, other substrates should be blended with sewage sludge to increase the total solid of the batch. Sorghum silage, sorghum pomace, and sorghum juice were added to the sewage sludge in various proportions during the research. As a result, the improvement of the biogas process, the stabilization of the biogas production curve, as well as the increase in methane yield were observed. The most biogas and methane were obtained from a mixture of sorghum juice (5%) and sewage sludge (664.8 Nm³∙Mg⁻¹ VS and 53.9%, respectively). Biogas production from other substrates based on sorghum and sewage sludge ranged from 457.4 to 588.8 Nm³∙Mg⁻¹ VS. For a mixture of juice (7%) and sewage sludge, the batch was acidified, and biogas production was only 281.5 Nm³∙Mg⁻¹ VS. Studies have shown that intelligent blending of an alternative raw material (compared to traditional maize silage) with sewage sludge allows for similar biogas yields while maintaining a stable anaerobic digestion process.

The aim of the conducted observations was to examine the effect of fertiliser produced based on plant digestate and resulting from the process of anaerobic fermentation of a substrate with sorghum (20%), beet (60%), rye (10%) and grass (10%) on the growth and yield of sorghum and corn. A strict, single-factor pot experiment was carried out in 2017–2018 in the Swojec Agricultural Experimental Unit at the University of Life Sciences in Wrocław. Fertilisation with digestate was the tested factor, with a focus on its influence on selected energy plants. Sucrosorgo sorghum and Atletico maize were analysed. During the research, the pots were placed in a vegetation hall. The research proved that the use of digestate-based fertiliser improves the productivity of both sorghum and maize, but only with an additional dose of basic macronutrients. The optimal variant is a fertiliser dose of 20 g enriched with 1.0 NPK. Increasing the dose to 30 g and 1.5 NPK generally did not result in a significant increase in plant height or in fresh and dry weights.