| ||The MELiSSA project|
MELiSSA (Micro-Ecological Life Support System Alternative) is a multidisciplinary project which has been conceived as a micro-organisms and higher plants based ecosystem intended as a tool to gain understanding of the behaviour of artificial ecosystems, and for the development of the technology for a future regenerative life support system for long term manned space missions - for example: a lunar base or a mission to Mars
The collaboration was established through a Memorandum of Understanding and is managed by ESA. It involves several independent organisations: University of Ghent (B), EPAS (B), University of Clermont Ferrand (F), SCK (B), SHERPA Engineering (F), VITO (B), University Autonoma of Barcelona (E) and University of Guelph (CDN). It is co-funded by ESA, the MELiSSA partners, the Belgium (SPPS), Spanish (CDTI) and Canadian (CRESTech, CSA) authorities. Contributions for specific studies have been received as well from Ireland and The Netherlands authorities.
The MELiSSA project is organised in five phases:
Phase 1: Basic research and development
Phase 2: Preliminary flight experiments
Phase 3: Ground and space demonstration
Phase 4: Technology transfer
Phase 5: Education and communication
The driving element of MELiSSA is the recovery of edible biomass from waste, carbon dioxide and minerals, using light as source of energy to promote biological photosynthesis. MELiSSA has five compartments colonised respectively by thermophilic anoxygenic bacteria, photoheterotrophic bacteria, nitrifying bacteria, photosynthetic bacteria and higher plants, and the crew. The liquefying compartment is the first step in the MELiSSA loop and determines the fraction of organic wastes (e.g. non edible parts of plant material, paper, ) that can be recycled in the loop. At present, around 70% degradation is achieved.
Currently, research is performed to test physical/chemical treatment of the remaining fraction in order to further improve the biodegradability. The improvement of the biodegradation efficiency by fungi is also investigated.
The CO2 that is produced in Compartment I is supplied to compartment IV (photosynthetic compartment). The volatile fatty acids and ammonia produced during the anaerobic fermentation process are fed to the second phototrophic anoxygenic compartment (Compartment II) where organic carbon is transformed into inorganic carbon source. Compartment III, or the nitrifying compartment, has as a main purpose the conversion of ammonia into nitrates. Nitrate is the most suitable nitrogen source for compartment IVb (Higher Plant). The oxidation of ammonium is carried out by Nitrosomonas europaea, and the oxidation of nitrite by Nitrobacter winogradskyi, both forming part of a naturally attached biofilm onto the BIOSTYR® beads surface. The fixed nature of the biofilm is ideal in this case due to the low growth rate of the cells and its high conversion activity.
The photoautotrophic compartment (compartment IV) is responsible for the removal of carbon dioxide, generation of edible biomass as food supply, water recovery and for the regeneration of oxygen for the crew. This compartment is divided into a photoautotrophic bacteria compartment, Arthrospira platensis, (compartment IVa) and a Higher Plant compartment (HPC) (compartment IVb), which allows better CO2 assimilation rates and gives a more balanced diet for the crew. Although not finalised, nowadays a total of 20 higher crops are included in the MELiSSA candidate list.
MELiSSA’s engineering, deterministic approach to an ecosystem is not only a tool to understand this complex system but also opens a new field of possible solutions in matters such as water and waste management and atmosphere. Its research work has produced around 100 scientific articles and many academic and technical reports.
Last update: 19 November 2007