Is Direct Methane Removal in Human Space Flight Required?

Environmental Control and Life Support (ECLS) is a major part of human space flight and habitation. Great care is taken to ensure an environment not only capable of supporting human life, but also one that is comfortable. One aspect of that habitable and comfortable environment is controlling trace contaminants in the atmosphere. The document the National Aeronautics and Space Administration (NASA) uses to govern the levels of specific compounds considered trace contaminants is the Spacecraft Maximum Allowable Concentrations (SMAC) for Selected Airborne Contaminants (JSC 20584) which is publicly available on the internet. While more attention is given to ammonia (NH3), propylene glycol (C3H8O2), and other physically toxic compounds, one of the most difficult atmospheric trace contaminants to remove directly is methane (CH4). Many technical papers have discussed the process of direct CH4 removal – what is required and potential future techniques to mature. This paper explores how to determine whether CH4 removal is required and the advantages or disadvantages associated with its implementation.