Valorization of methane from environmental engineering applications: A critical review

Wastewater and waste management sectors alone account for 18% of the anthropogenic methane (CH4) emissions. This study presents a critical overview of methanotrophs (methane oxidizing microorgan-isms) for valorizing typically discarded CH4 from environmental engineering applications, focusing on wastewater treatment plants. Methanotrophs can convert CH4 into valuable bioproducts including chemicals, biodiesel, DC electricity, polymers, and S-layers, all under ambient conditions. As discarded CH4 and its oxidation products can also be used as a carbon source in nitrification and annamox processes. Here we discuss modes of CH4 assimilation by methanotrophs in both natural and engineered systems. We also highlight the technical challenges and technological breakthroughs needed to enable targeted CH4 oxidation in wastewater treatment plants. (c) 2020 Elsevier Ltd. All rights reserved.