High precision of measurement of methane potential is important for the economic operation of biogas plants in the future. The biochemical methane potential (BMP) test based on the VDI 4630 protocol is the state-of-the-art method to determine the methane potential in Germany. The coefficient of variation (CV) of methane yield was >10% in several previous inter-laboratory tests. The aim of this work was to investigate the effects of inoculum and the digestion system on the measurement variability. Methane yield and methane percentage of five substrates were investigated in a Hohenheim biogas yield test (D-HBT) by using five inocula, which were used several times in inter- laboratory tests. The same substrates and inocula were also tested in other digestion systems. To control the quality of the inocula, the effect of adding trace elements (TE) and the microbial community was investigated. Adding TE had no influence for the selected, well- supplied inocula and the community composition depended on the source of the inocula. The CV of the specific methane yield was <4.8% by using different inocula in one D-HBT (D-HBT1) and <12.8% by using different digestion systems compared to D-HBT1. Incubation time between 7 and 14 days resulted in a deviation in CV of <4.8%.

To be able to meet the European Union’s energy and climate targets for 2030, all member states need to rethink their energy production and use. One potential renewable energy source is biogas. Its role has been relatively small compared to other energy sources, but it could have a more central role to solve some specific challenges, e.g., to reduce carbon dioxide (CO₂) emissions from traffic, or to act as a buffer to balance electricity production with consumption. This research analyses how the future of the biogas business in three case study countries is developing until 2030. The study is based on experts’ views within the biogas business branch in Germany, The Netherlands, and Finland. Both similarities and differences were found among the experts’ answers, which reflected also the current policies in different countries. The role of biogas was seen much wider than just to provide renewable energy, but also to decrease emissions from agriculture and close loops in a circular economy. However, the future of the biogas branch is much dependent on political decisions. To be able to show the full potential of biogas technology for society, stable and predictable energy policy and cross-sector co-operation are needed.

Anaerobic digestion (AD) produces bioenergy and bio-fertilizer. However, weed seeds can contaminate the substrates for biogas production. This work assesses seed viability of four weeds species origin from Germany and China under AD conditions at 37, 42 and 52 °C with different retention times. All investigated seeds were inactivated after 12 h at 52 °C, 128 h at 42 °C and 512 h at 37 °C under AD treatment. Inactivation duration varying between species and a global test showed that the countries of seeds origin have a significant effect on inactivation times. For two species, by contrast, short treatment times increased the germination rate which increases the risk of weed dispersal. An anoxic water bath treatment with identical temperatures resulted in longer deactivation times, indicating that other factors also play a role in the weed seeds elimination. The results indicate that the risk of weed seed spreading through digestate application can be minimized by an adequate retention time.

Germany (DE) and China (CN) have different political approaches in supporting the biogas sector. Three German and three Chinese large-scale biogas plants (BGPs) were evaluated as part of a year-round monitoring program. Laboratory methods were utilized to analyze the chemical indicators. Results showed a stable anaerobic digestion process without system failures in all BGPs. The methane yield had a range of 0.23–0.35 m³_CH4/kg_ODM for DE BGPs and 0.11–0.22 m³_CH4/kg_ODM for CN BGPs, due to different substrates and working temperatures. Financial analyses indicated that DE BGPs are viable under their current feed-in tariffs contracts. Their financial internal rate of return (IRR) ranged between 8 and 22%. However, all CN BGPs had negative IRRs, indicating that they are financially unfeasible. Risk analyses illustrated that DE BGPs will face financial nonviability if benefits decrease by 9–33% or costs increase by 10–49%, or if a combined worse case (benefit decrease and cost increase) of 5–20% occurs. Incentives to BGP operations are particularly important in China, where the government should consider switching the construction-based subsidy to a performance-based subsidy system to motivate the operators. BGP monitoring is necessary to understand the performance, in addition to briefing policymakers in case a policy reform is needed.