Recycling for a trip to Mars

The first manned trip to Mars may seem a long way in the future but the European Space Agency (ESA) is already working to solve the problem facing every traveller - just how do you fit everything you need in one suitcase?

Not only will the first astronauts on Mars need to fit everything for a 3-year trip into one small spacecraft; they will not be able to throw anything away, including human waste.

ESA has developed a new system called MELISSA (Micro-Ecological Life Support Alternative) to test ways of turning such waste into food, oxygen and water by creating an artificial ecosystem which uses micro-organisms to process the waste to use as fertiliser to grow plants.

Designed to be fully up and running by 2005, the MELISSA project is the first of its kind to recycle organic waste for food production. The recycling systems used on Mir or the International Space Station currently only purify water and recycle exhaled carbon dioxide.

The MELISSA recycling system, which is currently being built near Barcelona, Spain, will consist of five separate, interconnected, compartments. In three of them, waste will be progressively broken down by different fermentation processes. In the fourth compartment, algae and plants will grow to produce food, oxygen and water. The fifth "compartment" is where the consumers will live.

The MELISSA design imitates the structure of a terrestrial lake with sludge (raw waste) at the bottom which undergoes anaerobic (without oxygen) fermentation in darkness. Above the sludge is light but no oxygen. Higher still oxygen is present and it is here that ammonia can be converted into nitrate. At the surface, carbon dioxide, oxygen and light are present, allowing plants to thrive here.

So far, small models of the three fermentation chambers have been built. The models will be replaced by larger chambers with 50-100 litre capacity each. The fourth chamber, where higher plants are grown, is under development at the University of Guelph in Canada which recently opened a new facility for growing plants at the sort of low pressure found in space.

The size of MELISSA will ultimately depend on the number of astronauts using it and the quality of the food required. First estimates show that a wheat area of 10 square metres could supply enough food for 1 person. Much less space will be needed to grow algae. So the final design of the MELISSA system may depend on what the astronauts fancy for lunch.

- NEWSTREAM