Operation overview of a biological waste treatment system during the 4-crew 180-day integrated experiment in the controlled ecological life support system (CELSS)

Waste management and treatment is vital to health care and material circulation, especially in the Controlled Ecological Life Support System (CELSS) with finite resources for long-duration manned space missions. A closed ecological-cycle integrated 4-crew 180-day experiment platform was established to investigate the key technologies such as effective cultivation of higher plant, water treatment and recycling, waste management and treatment. In this study, generated waste during the integrated experiment was classified as renewable and non-renewable waste. The renewable waste including all crew feces and part of inedible plant biomass were treated in a biological system where the aerobic composting technology was utilized. The performance in relation to degradation effect, phytotoxicity and nutrient evaluation was examined during the continuous 180 days. The long-term operation results displayed that 96.26 kg feces and 74.4 kg wheat straw were treated, and 90.6 kg compost product was discharged in nine batches. The microbial community variation was analyzed and Firmicutes, Actinobacteria and Proteobacteria enriched in the compost. The phytotoxicity of compost was examined by seed germination index (GI) and GI of Chinese cabbage ranged from 88% to 132% for all batches. Compared to grown in vermiculite only, the lettuce yield increased 19% when grown in a mixture of vermiculite and processed compost. The summary of this work will be helpful to facilitate future applications of aerobic composting technology as the bio-based waste treatment technology in CELSS.