Microbial Mayhem: Microbial Growth Potential in CO2 Removal Systems Designed for Long-Duration Spaceflight

Crewed missions that venture into deep space require extremely robust life support systems. Amongst these systems is the CO2 removal system, which helps ensure the recirculation of breathable air to crew. To travel to Mars, a new CO2 removal system is needed. Two candidate systems are in development at the NASA Ames Research Center (ARC): Liquid Amine CO2 Removal (LACR) and CO2 Cold Surface Deposition (CDep). Engineering constraints are important in the design process, but biological problems must also be considered; Microbial growth has been detected on a multitude of surfaces on the International Space Station (ISS) and has been shown to cause problems on several occasions due to biofilm formation inhibiting system performance. Should the new CO2 removal system be susceptible to microbial growth, its performance could be hindered and crew health threatened on future long-duration missions. To investigate this possibility, existing relevant literature was thoroughly reviewed for these two ARC candidate systems. The results show that both systems have components that are potentially susceptable for problematic microbial growth. Therefore, wet lab testing to measure performance degradation was designed using dry and wet biofilm-forming species that have been found on the ISS. Further testing was devised to determine the quantity and species of microbes most likely to enter a CO2 removal system by determining the efficiency of charcoal-HEPA filters that filter incoming air. This work will inform the design and preventative measures that NASA will take to avoid problematic microbial growth in future CO2 removal systems.