Greenhouse gas emissions are a significant driver of global climate change. Especially methane, a much stronger greenhouse gas than carbon dioxide, has gained attention because of emissions from increased microbial activity in thawing permafrost and the dissolution of marine methane hydrates as a consequence of ocean warming. There are also important human-made methane sources, for example, anaerobic digesters and anaerobic granular systems for wastewater treatment. In these reactor types, organic matter is purposely converted to methane to render the chemical energy captured in waste organic matter accessible for human activities, i.e., by using methane as a renewable fuel. Ideally, this human-made methane never leaves the controlled environments of the bioprocess. This is, however, not the case in reality, as along with the treated water, dissolved methane is continuously leaving the reactor and eventually finds its cataclysmic way into the atmosphere by degassing. This loss is significantly reducing and possibly offsetting the positive environmental effect of generating a renewable energy.
In this project, we will develop an innovative bioprocess to remove methane traces from the effluent of anaerobic reactors by oxidizing excess methane to CO2 by methanotrophic bacteria. Methanotrophs require a terminal electron acceptor that would ideally be oxygen. However, simply providing oxygen by traditional means, i.e., by bubbling, would accelerate the process of losing methane to the atmosphereand is therefore unacceptable. Instead, we suggest a novel, aeration-free process for methane elimination based on the syntrophic interactions between phototrophic and heterotrophic bacteria forming oxygenic photogranules. This bioprocess will improve the environmental fingerprint of anaerobic bioreactors, hence reduce the global warming potential of biogas processes in general.