The regulation of CO2 levels in a BLSS by controlling the solid waste treatment unit

Abstract A bioregenerative life support system (BLSS) is an artificial closed ecosystem which provides basic human life support for long-duration and far-distance space activities such as lunar bases. “Lunar Palace 1”, an experimental facility, was constructed by our team for the integration research of the key technologies in BLSS, and then a continuous 105-day closed integrative BLSS experiment was carried out in “Lunar Palace 1”(Stage I) successfully last year. In such a system, O2 produced by higher plants is supplied for the breathing of the crew, as well as the respiration of microorganisms which decompose the solid wastes such as inedible plant biomass and human wastes, while CO2 produced by the crew and microorganisms is provided for plants to grow. In the system, an excessively high CO2 level can affect plant growth and may harm human health, however, if the CO2 level is too low, plant growth may also be inhibited. Thus, keeping the balance between CO2 and O2 levels is essential to the gas regulation in the system, and is one of the key points for the operation stability of the system. In this study, an efficient and controllable solid waste bio-convertor was built based on the microbial fermentation in “Lunar Palace 1”, and the CO2 generation of the bio-convertor under the optimum fermentation conditions in the 105-day airtight experiment was monitored. Moreover, the changes of CO2 production along with increasing or reducing the temperature of the bio-convertor from 33 to 45 °C (or from 45 to 33 °C) were also investigated, and a positive correlation between the CO2 output and the fermentation temperature was obtained accordingly. Therefore, the CO2 production can be adjusted effectively by changing the temperature of the bio-convertor, which implies that it is feasible to regulate the balance between the CO2 and O2 concentrations in BLSS by controlling the fermentation conditions of the solid waste treatment unit. The results of this study could lay a foundation for the following researches conducted in “Lunar Palace 1”.

[1]  V. S. Kovalev,et al.  A conceptual configuration of the lunar base bioregenerative life support system including soil-like substrate for growing plants , 2008 .

[2]  Kanapathipillai Wignarajah,et al.  Reactive Carbon from Life Support Wastes for Incinerator Flue Gas Cleanup , 2000 .

[3]  R M Wheeler,et al.  Comparison of aerobically-treated and untreated crop residue as a source of recycled nutrients in a recirculating hydroponic system. , 1996, Advances in space research : the official journal of the Committee on Space Research.

[4]  X. Zhou,et al.  Biological degradation and composition of inedible sweetpotato biomass. , 1996, Advances in space research : the official journal of the Committee on Space Research.

[5]  M. S. Finstein,et al.  Effect of Temperature, Aeration, and Moisture on CO2 Formation in Bench-Scale, Continuously Thermophilic Composting of Solid Waste , 1977, Applied and environmental microbiology.

[6]  Hong Liu,et al.  Chlorella vulgaris culture as a regulator of CO2 in a bioregenerative life support system , 2013 .

[7]  Scott B. Jones,et al.  Comparison of three soil-like substrate production techniques for a bioregenerative life support system , 2010 .

[8]  J I Gitelson,et al.  Consistency of gas exchange of man and plants in a closed ecological system: lines of attack on the problem. , 1996, Advances in space research : the official journal of the Committee on Space Research.

[9]  P. Trumbo,et al.  Evaluation of Cyanothece sp. ATCC 51142 as a candidate for inclusion in a CELSS. , 1996, Advances in space research : the official journal of the Committee on Space Research.

[10]  Leyuan Li,et al.  Characteristics of the soil-like substrates produced with a novel technique combining aerobic fermentation and earthworm treatment , 2012 .

[11]  Guanghui Liu,et al.  Low light intensity effects on the growth, photosynthetic characteristics, antioxidant capacity, yield and quality of wheat (Triticum aestivum L.) at different growth stages in BLSS , 2014 .

[12]  Qifei Huang,et al.  Accumulated Temperature as an Indicator to Predict the Stabilizing Process in Sewage Sludge Composting , 2002 .

[13]  M P Alazraki,et al.  Evaluation of an anaerobic digestion system for processing CELSS crop residues for resource recovery. , 1997, Advances in space research : the official journal of the Committee on Space Research.

[14]  H. Insam,et al.  Hydrolase activities, microbial biomass and bacterial community in a soil after long-term amendment with different composts , 2006 .

[15]  M Czupalla,et al.  The conceptual design of a hybrid life support system based on the evaluation and comparison of terrestrial testbeds. , 2005, Advances in space research : the official journal of the Committee on Space Research.

[16]  Hong Liu,et al.  Feasibility of feeding yellow mealworm (Tenebrio molitor L.) in bioregenerative life support systems as a source of animal protein for humans , 2013 .