C.R.O.P. – Combined Regenerative Organic food Production: Using Trickling Filters for Nitrate Production from Urine

Abstract

The DLR Project C.R.O.P. generally aims to combine the utilization of all kinds of organic wastes with soilless plant cultivation. Within the project scientific work is divided into several research areas that are allotted to different groups. Our group is concerned with the waste management system, in which nutrients should be recycled to the highest possible degree. The core of the system is formed by microbial trickling filters in which organic matter is liquefied if needed, and converted into inorganic compounds. The resulting nutrient solution is intended for fertigation in greenhouse cultures in space and on Earth. In our testing facility at DLR the capability of the filters to convert urine into a nitrate containing solution is characterized. Each filter unit combines 30 l of liquid volume with 6 l of filter volume. Running the filters with diluted synthetic urine in different starting concentrations (7 %, 20 %) to simulate yellow water showed that the process of urea conversion as it occurs in the soil also worked in the filters. Even when nitrogen content far exceeded the concentrations usually found in wastewaters ammonia was turned over quickly and odour nuisance and toxicity were reduced to a minimum. Nitrate production occurred at rates of 45 g per day at a maximum, which corresponds to a urea degradation rate of 22.5 g per day. The use of the resulting solution as fertilizer is currently tested experimentally