Microalgae cultivation for space exploration: Assessing the potential for a new generation of waste to human life-support system for long duration space travel and planetary human habitation

One of the challenges of long duration NASA missions, such as human transportation and habitation of the moon and/or Mars, is the limited life-support resources that can be taken onboard. These missions would benefit from processes or systems that can provide sustainable close-loop, life-support functions such as O2 regeneration from CO2, supplemental food provision, and water remediation. In cases of long duration human planetary/moon habitation, life-support systems that can utilize local resources (i.e., CO2 in Mars? atmosphere) could dramatically increase mission success. Processes of these nature could profoundly reshape space systems? design and configurations, improve mission flexibility, provide a higher degree of astronaut life-support on-site independence, and pave the way to novel routes of producing life-support materials in space. In this work, the potential of integrating a microalgal system into the existing life-support system within the International Space Station (ISS) was assessed. Two well-studied microalgal species (Chlorella vulgaris and Arthrospira platensis) were considered for both suspended and attached-growth cultivation. The assessment suggested that attached-growth cultivation of A. platensis using urine and flush water within the ISS could provide significant amounts of reclaimed O2 and food supplement (biomass) using the least reactor (wet) volume. However, the sustainability of the microalgal system will necessitate continuous supplements of N and P from external sources or from other waste streams within the ISS. This work highlights the potential and limitations of integrating microalgae into the existing life-support system in the ISS. This integration would provide the capability to produce food supplement (biomass), which is critical for long duration manned missions.