Researchers at the Norwegian Institute of Bioeconomy Research (NIBIO) and the Norwegian University of Life Sciences have developed a biofilm-based process that converts carbon dioxide and syngas into biomethane with purity levels exceeding 96%.
The method uses thin microbial layers to produce renewable gas under oxygen-free conditions and could support the development of circular carbon systems.
These anaerobic conditions allow the biofilm layers to absorb and metabolise CO2 or carbon monoxide into methane. This is different from traditional biogas methods that decompose organic waste such as manure.
“Instead of decomposing organic waste, as is done in traditional biogas production, the biofilm method captures and processes gas streams using self-selected microorganisms harboured within thin biofilm under oxygen-free conditions,” said Dr Lu Feng, Research Scientist – Division of Environment and Natural Resources at NIBIO.
Researchers also employed bioaugmentation, which involves adding methane-producing microbes to steer and enhance the biomethane yield.
Small plastic biofilm carriers from Biowater Technology, commonly used in water and wastewater treatment, provide a surface for beneficial bacteria to grow and function efficiently. ©Lu Feng
The experiments took place in bioreactors where microorganisms like Methanothermobacter grew on surfaces, forming the biofilms. In addition to enhancing gas-to-methane conversion, the biofilm structure helps protect the microbes from toxins like hydrogen sulphide.
A statement from NIBIO noted that “systems without biofilm lost up to 30% of the methane, while the biofilm reactors maintained high methane quality even at extremely high hydrogen sulphide content.”
Beyond CO2, the technique also works with syngas – a combination of hydrogen and carbon monoxide – potentially enabling conversion of plastic waste or woody biomass into biomethane. Controlled hydrogen addition was critical, however, to maintain system balance.
“This shows that biofilm reactors have great potential, but also that they require careful control to function optimally at industrial scale,” said Dr Feng.
“Biofilm-based processes offer a … platform for future biogas production. This could become an important contribution to reducing harmful gas emissions while producing renewable energy,” he added.
