Combined Regenerative Organic-food Production: An integrated approach to the utilization of yellow water and other organic wastes

Abstract

Bioregeneration is a key requirement of life support systems for long-term manned space missions. According to this, C.R.O.P. is a concept for the recycling of organic wastes and wastewaters, which combines microbial trickle filters for waste processing with plant cultivation on the basis of the resulting nutrient containing solutions. Besides phosphates and other ions necessary for plant growth, yellow water contains a high proportion of urea, which is a prospective source of nitrogen for plants. To make the contained nitrogen available for plants, it has to be converted into one of its ionic compounds. In the soil, urea is converted into nitrate in a multi-step process involving ammonia as an intermediate. Ammonia can be resorbed by plants but it is responsible for the foul odour of stored urine. The C.R.O.P. trickle filters are filled with porous lava rock particles on the rough surface of which a community of soil bacteria is established. Running the filters with diluted synthetic urine to simulate yellow water showed that the process of urea conversion as it occurs in the soil also works in the filters. Ammonia is turned so quickly into nitrate that odour nuisance and toxicity are reduced to a minimum. The resulting solution can be used for fertilizer production or soil free plant cultivation in a hydroponic system. A C.R.O.P. system combining trickle filters for waste processing with hydroponic plant cultivation facilities can be easily modified for use in space thus providing the bioregenerative compartment of a modular life support system.