Solid waste processing in a CELSS: nitrogen recovery.

Life support technologies are being developed for long-duration space missions at NASA Ames Research Center as part of the Controlled Ecological Life Support System (CELSS) Program. The primary goal of the CELSS Program is to develop small-scale ecological systems, a CELSS, that mimic ecological systems on Earth. This small-scale replica CELSS can provide all of the necessary life support functions and recycle nearly 100% of the waste products. A CELSS will use plants to purify air, clean water, and generate food for a human habitat. Human and plant waste products will be converted to useful products and reintroduced into the plant and human habitats for consumption. Both physical/chemical and biological waste-processing systems may be utilized to recycle waste materials. Recovering nitrogen from waste products is a major concern because nitrogen is an important nutrient for plants and humans. This article will outline plant selection requirements and waste-processing requirements, characterize waste streams, and discuss the potential physical/chemical waste processors used to process the wastes and the fate of nitrogen as a result of the process employed.