Mars Academy

Waste Recycling

Our mission to Mars will require large amounts of air, food, and water to sustain humans in space.  The launch and onboard storage costs of these resources is prohibitive.  These factors drive the need to minimize the amount of materials that need to be launched into space and maximize the recycling of waste products into usable products.
Some of the major waste streams produced are listed below:

- urine
- feces
- grey waters (from sanitary and wash streams)
- food preparation waters
- sweat, breath
- gaseous
- solid (miscellaneous refuse, trash, paper, plastics etc.)

An average astronaut produces a waste stream of some 67 pounds total in one day!

An interesting possibility to process biological wastes is Microwave Incineration.  

Microwave Incineration is a means of oxidizing inedible plant matter into carbon dioxide and water that can inturn be used by plants in plant growth chambers. Incineration of solid waste is one of the most effective ways to reduce the amount of waste that is discarded, for the reason that microwave incineration is easy to use, is compact, is safe, versatile, the emissions are clean and environmentally safe and it is simple to hook up.  Incineration also ensures protection from infectious diseases.

The microwave Incinerator has two chambers.  The secondary chamber is mounted above the primary chamber, and a gas passage tube separates the two chambers.  The gases resulting from the decomposition of waste in the primary chamber pass to the secondary chamber where they are ignited.  The temperature of the flame is 1000ºC to 1200ºC.  A catalyst bed is contained within the secondary chamber which consists of platinum group metals supported in a honeycomb.  This catalyst is preheated using an electrical heater using microwaves at 2450 MHz.  When the waste is heated, it begins to loose moisture in the regions near the top surface.  As drying on the surface of the waste progresses, microwaves penetrate further into the waste until almost all of the moisture is removed.  

Gases resulting from the decomposition of waste in the primary chamber and products of the flame pass through the catalyst honeycomb where they are oxidized.  After a period of two hours, the incineration is complete, and the unit enters a cool down mode.  Through the process, waste products have undergone a series of reactions to produce ash, which has only 10% of the mass of the original waste, and is easy to discard and is free of infections.