Methane emission reduction strategies and determination of emission factors at biogas plants

Methane is produced during anaerobic digestion in biogas plants. As methane is a very effective greenhouse gas, emissions should be avoided as far as possible, in order to ensure a clean and environmentally friendly operation.

The project ""EvEmBi - Evaluation and reduction of methane emission from different biogas plant concepts"" (funded within the 11th ERA-NET bioenergy call) started in April 2018. The project is based on the findings from the previous project ""MetHarmo - European harmonisation of methods to quantify methane emissions from biogas plants"" (funded within the 9th ERA-NET bioenergy call). In ""MetHarmo"", different measurement methods for determining methane emissions were investigated and compared. Both, measurement methods to quantify methane emissions from single emission sources, as well as methods to quantify the overall plant emissions were considered. Suitable approaches and recommendations for the measurements at biogas plants were described in a joint document. These recommendations are considered and applied in the methane emission measurements of biogas plants, which will be carried out during the ""EvEmBi"" project, as well. Partners from various European countries are involved in ""EvEmBi"", including Austria, Denmark, Germany, Sweden and Switzerland.

Within the ""EvEmBi"" project, the existing technologies at biogas plants in the mentioned European countries were evaluated with regard to their methane emissions. Based on these results, strategies to reduce these emissions are deduced. In a first step, measurements to quantify the methane emissions at different biogas plant concepts are carried out in the participating countries. Both, emissions from single sources as well as from the whole biogas plant are quantified. In a second step, mitigation strategies are developed and applied at some exemplary plants to reduce the methane emissions at these plants. The success of these mitigation measures are going to be verified with further emission quantification measurements at those plants.

A further objective during the ""EvEmBi"" project is the determination of emission factors (EFs) from individual biogas plant technologies and its transfer to EFs of the entire plant inventory of the particular countries. For that, a model for quantifying the emission factor by using statistical information about the emissions from different plant components and about the distribution of certain technologies in the biogas plant inventory will be developed.

For a sustainable contribution of this project towards the reduction of emissions at biogas plants, ""EvEmBi"" aims for the dissemination of project findings and knowledge within the consortium concerning emission mitigation strategies at biogas plants. To this end, training concepts will be developed. These training concepts are used in national workshops for operators and one international webinar carried out by the European Biogas Association (EBA). National position papers and a European position paper, which also proposes concrete recommendations for a voluntary system to reduce emissions, will be developed during the project.

In this presentation, first results about the emission measurements of the individual biogas plant components will be presented and a concept to transfer the emissions of the individual sources in a statistical model to quantify the emission factors will be introduced.