The waste compartment is a critical and challenging step that needs to deal with solid waste of heterogeneous nature. As a result, several R&D challenges need to be addressed to ensure its optimal and safe operation.
Firstly, the waste compartment unit is currently operated using an enriched, but undefined, mixed microbial community, able to degrade different types of substrates. It is important to understand how these bio-transformations take place, by which organisms and under what conditions. Only by fully comprehending the systems it will be possible to adapt and control its function and, ultimately, move into a defined mixed culture.
Secondly, current research activities have demonstrated it is possible to process complex wastes in the MELISSA waste compartment. However, degradation efficiency should be improved to maximize the recovery of resources within the regenerative life support system. In line with that, volatile fatty acid profile obtained should be adequate for further conversion in the subsequent units, especially the C2 compartment or the photosynthetic ones C4 A&B.
Lastly, future research should demonstrate the stability of the community (both genetic and in terms of function) under space conditions (as discussed below).