MELiSSA is a micro-organisms and higher plant based ecosystem conceived as a tool for understanding the behavior of artificial ecosystems and developing the technology for a future Biological Life Support System for long term manned space missions. The liquefying compartment is responsible for the anaerobic biodegradation of human faecal material and other wastes generated by the crew.
At thermophilic conditions, without pre-treatment of the faecal material, the overall biodegradation efficiency was 30% (Demey, 1998). The biodegradation is limited due to the presence of slowly biodegradable fibrous material such as lignin, xylan and cellulose.
In a first series of experiments to improve the biodegradation, the faecal material was pretreated with the commercial enzymes cellulase and xylanase. Two anaerobic reactors were set up. The first reactor was fed with fresh faecal material and the second reactor was fed with pretreated cake from the first reactor. A total conversion efficiency of 53% was reached. Protein were converted for 70% and fibres for 44%.
A second series of tests were started in which the faecal material was pretreated with H2O2 and laccase. H2O2 is a strong oxidiser and is able to attack non-biodegradable material. From the results can be concluded that 8% of the faecal material is degraded after the addition of H2O2 and laccase and 56% of the pretreated cake is converted by the inoculum of the MELiSSA anaerobic reactor.