Technical Report

Reduction of methane emissions from biogas systems and landfills

Methane oxidation treatment for systems with low gas fluxes and low methane concentrations

February 2025

Methane has a large global warming potential and is a significant contributor to the current warming of the atmosphere, accounting for one third of net warming since the Industrial Revolution. To address the importance of its climate impact, an international campaign to reduce global methane emissions was launched at COP 26 in Glasgow, Scotland in 2021. As of January 2025, the Global Methane Pledge has 159 country participants who have agreed to take actions to contribute to a collective effort to reduce global emissions at least 30 percent from 2020 levels by 2030.

Methane is emitted from a wide range of industrial, agricultural and waste management processes. The capture and treatment of emissions are not always technically and, under current conditions, not always economically feasible. A particular challenge is posed by waste gas streams with low methane concentrations, and low and variable volumetric flowrates. The treatment of such waste gas streams becomes expensive and technically difficult if the quantities collected are small. Its low energy content makes energy recovery difficult and oxidation, without extra energy supply, is only possible with complex technology. For biogas systems and landfills, examples of emission sources with low methane contents and low volumetric flowrates include:

• Anaerobic digestion and biogas utilization (biogas plants)
• • feedstock (including manure) handling and storage,
  • off gases of Combined Heat and Power (CHP) units,
  • off gases from biogas upgrading,
  • open and non-gas tight digestate storage,
  • Processes related to biogas plants such as digestate composting, organic waste handling, etc.;
• Landfills
• • landfill gas that is highly diluted with air due to leaks in gas collection or increasing air content in older, closed landfills.

Methane oxidation, through thermochemical or biochemical means, can serve as an effective treatment option for some of these emission sources, eliminating the methane as well as volatile organic compounds. For thermochemical solutions, complete methane oxidation requires high temperatures within the incineration process. This temperature should be provided from the gas to be treated, which is also the fuel gas in order to be able to ensure an autothermic process. Therefore, these solutions depend significantly on the energy content of the fuel respective of the gas to be treated and thus the methane concentration of the gas to be treated. Methane can also be used as an energy source by microorganisms who convert it into carbon dioxide and water. Biochemical processes have been used in landfill aftercare to minimize methane escaping into the atmosphere. Here, technical filters, operated in active or passive modes, can facilitate the work of microorganisms to use the oxygen that diffuses into the cover layer to oxidize the methane emissions. Biochemical oxidation is less developed than thermochemical treatment, but appears to offer options when thermochemical solutions reach their technical limits.

This report presents process technologies for methane oxidation, with a focus on processes that can convert waste gases with low methane concentrations emitted at low flow rates. It begins by describing the properties of methane and the climate change impacts that can result from relatively small sources of emissions (Section 2), and then introduces several emission sources at biogas plants and landfills (Section 3). This is followed by a review of the principles of methane oxidation (Section 4), the technical boundary conditions (Section 5) and a description of the technologies and the applications for which they are best suited (Section 6). Energy considerations are briefly covered in Section 7, and a financial analysis of Regenerative Thermal Oxidation (RTO) technology is presented in Section 8.

The report concludes with examples of real-world applications of methane oxidation technologies.

This work was completed by Members of IEA Bioenergy Task 37 representing Germany, Denmark, Finland and Canada, and is a deliverable for the 2022-2024 Triennium work programme.