Synthesis of biomass and utilization of plants wastes in a physical model of biological life-support system

The paper considers problems of biosynthesis of higher plants' biomass and "biological incineration" of plant wastes in a working physical model of biological LSS. The plant wastes are "biologically incinerated" in a special heterotrophic block involving Californian worms, mushrooms and straw. The block processes plant wastes (straw, haulms) to produce soil-like substrate (SLS) on which plants (wheat, radish) are grown. Gas exchange in such a system consists of respiratory gas exchange of SLS and photosynthesis and respiration of plants. Specifics of gas exchange dynamics of high plants--SLS complex has been considered. Relationship between such a gas exchange and PAR irradiance and age of plants has been established. Nitrogen and iron were found to the first to limit plants' growth on SLS when process conditions are deranged. The SLS microflora has been found to have different kinds of ammonifying and denitrifying bacteria which is indicative of intensive transformation of nitrogen-containing compounds. The number of physiological groups of microorganisms in SLS was, on the whole, steady. As a result, organic substances--products of exchange of plants and microorganisms were not accumulated in the medium, but mineralized and assimilated by the biocenosis. Experiments showed that the developed model of a man-made ecosystem realized complete utilization of plant wastes and involved them into the intrasystem turnover.     

Physical-chemical treatment of wastes: a way to close turnover of elements in LSS.

"Man-plants-physical-chemical unit" system designed for space stations or terrestrial ecohabitats to close steady-state mineral, water and gas exchange is proposed. The physical-chemical unit is to mineralize all inedible plant wastes and physiological human wastes (feces, urine, gray water) by electromagnetically activated hydrogen peroxide in an oxidation reactor. The final product is a mineralized solution containing all elements balanced for plants' requirements. The solution has been successfully used in experiments to grow wheat, beans and radish. The solution was reusable: the evaporated moisture was replenished by the phytotron condensate. Sodium salination of plants was precluded by evaporating reactor-mineralized urine to sodium saturation concentration to crystallize out NaCl which can be used as food for the crew. The remaining mineralized product was brought back for nutrition of plants. The gas composition of the reactor comprises O2, N2, CO2, NH3, H2. At the reactor's output hydrogen and oxygen were catalyzed into water, NH3 was converted in a water trap into NH4 and used for nutrition of plants. A special accessory at the reactor's output may produce hydrogen peroxide from intrasystem water and gas which makes possible to close gas loops between LSS components.     

Light intensity and production parameters of phytocenoses cultivated on soil-like substrate under controlled [correction of controled] environment conditions.

To increase the degree of closure of biological life support systems of a new generation, we used vermicomposting to involve inedible phytomass in the intra-system mass exchange. The resulting product was a soil-like substrate, which was quite suitable for growing plants (Manukovsky et al. 1996, 1997). However, the soil like substrate can be regarded as a candidate for inclusion in a system only after a comprehensive examination of its physical, chemical, and other characteristics. An important criterion is the ability of the soil-like substrate to supply the necessary mineral elements to the photosynthesizing component under the chosen cultivation conditions. Thus, the purpose of this work was to study the feasibility of enhancing the production activity of wheat and radish crops by varying the intensity of photosynthetically active radiation, without decreasing the harvest index. The increase of light intensity from 920 to 1150 micromoles m-2 s-1 decreased the intensity of apparent photosynthesis of the wheat crops and slightly increased the apparent photosynthesis of the radish crops The maximum total and grain productivity (kg/m2) of the wheat crops was attained at the irradiance of 920 micromoles m-2 s-1. Light intensity of 1150 micromoles m-2 s-1 decreased the productivity of wheat plants and had no significant effect on the productivity of the radish crops (kg/m2) as compared to 920 micromoles m-2 s-1. The qualitative and quantitative composition of microflora of the watering solution and substrate was determined by the condition of plants, developmental phase and light intensity. By the end of wheat growth under 1150 micromoles m-2 s-1 the numbers of bacteria of the coliform family and phytopathogenic bacteria in the watering solution and substrate were an order of magnitude larger than under other illumination conditions. The obtained data suggest that the cultivation of plants in a life support system on soil-like substrate from composts has a number of advantages over the cultivation on neutral substrates, which require continual replenishment of the plant nutrient solution from the system's store to complement the macro- and micro-elements. Yet, a number of problems arise, including those related to the controlling of the production activity of the plants by the intensity of photosynthetically active radiation. It is essential to understand why the intensity of production processes is limited at higher irradiation levels and to overcome the factors responsible for this, so that the soil-like substrate could have an even better chance in the competition for the best plant cultivation technology to be used in biological life support systems.     

Mass exchange in an experimental new-generation life support system model based on biological regeneration of environment.

An experimental model of a biological life support system was used to evaluate qualitative and quantitative parameters of the internal mass exchange. The photosynthesizing unit included the higher plant component (wheat and radish), and the heterotrophic unit consisted of a soil-like substrate, California worms, mushrooms and microbial microflora. The gas mass exchange involved evolution of oxygen by the photosynthesizing component and its uptake by the heterotroph component along with the formation and maintaining of the SLS structure, growth of mushrooms and California worms, human respiration, and some other processes. Human presence in the system in the form of "virtual human" that at regular intervals took part in the respirative gas exchange during the experiment. Experimental data demonstrated good oxygen/carbon dioxide balance, and the closure of the cycles of these gases was almost complete. The water cycle was nearly 100% closed. The main components in the water mass exchange were transpiration water and the watering solution with mineral elements. Human consumption of the edible plant biomass (grains and roots) was simulated by processing these products by a unique physicochemical method of oxidizing them to inorganic mineral compounds, which were then returned into the system and fully assimilated by the plants. The oxidation was achieved by "wet combustion" of organic biomass, using hydrogen peroxide following a special procedure, which does not require high temperature and pressure. Hydrogen peroxide is produced from the water inside the system. The closure of the cycle was estimated for individual elements and compounds. Stoichiometric proportions are given for the main components included in the experimental model of the system. Approaches to the mathematical modeling of the cycling processes are discussed, using the data of the experimental model. Nitrogen, as a representative of biogenic elements, shows an almost 100% closure of the cycle inside the system. The proposed experimental model of a biological system is discussed as a candidate for potential application in the investigations aimed at creating ecosystems with largely closed cycles of the internal mass exchange. The formation and maintenance of sustainable cycling of vitally important chemical elements and compounds in biological life support systems (BLSS) is an extremely pressing problem. To attain the stable functioning of biological life support systems (BLSS) and to maintain a high degree of closure of material cycles in than, it is essential to understand the character of mass exchange processes and stoichiometnc proportions of the initial and synthesized components of the system.     

Biological and physiochemical methods for utilization of plant wastes and human exometabolites for increasing internal cycling and closure of life support systems.

Wheat was cultivated on soil-like substrate (SLS) produced by the action of worms and microflora from the inedible biomass of wheat. After the growth of the wheat crop, the inedible biomass was restored in SLS and exposed to decomposition ("biological" combustion) and its mineral compounds were assimilated by plants. Grain was returned to the SLS in the amount equivalent to human solid waste produced by consumption of the grain. Human wastes (urine and feces) after physicochemical processing turned into mineralized form (mineralized urine and mineralized feces) and entered the plants' nutrient solution amounts equal to average daily production. Periodically (once every 60-70 days) the nutrient solution was partly (up to 50%) desalinated by electrodialysis. Due to this NaCl concentration in the nutrient solution was sustained at a fixed level of about 0.26%. The salt concentrate obtained could be used in the human nutrition through NaCl extraction and the residuary elements were returned through the mineralized human liquid wastes into matter turnover. The control wheat cultivation was carried out on peat with use of the Knop nutrient solution. Serial cultivation of several wheat vegetations within 280 days was conducted during the experiment. Grain output varied and yield/harvest depended, in large part, upon the amount of inedible biomass returned to SLS and the speed of its decomposition. After achieving a stationary regime, (when the quantity of wheat inedible biomass utilized during vegetation in SLS is equal to the quantity of biomass introduced into SLS before vegetation) grain harvest in comparison with the control was at most 30% less, and in some cases was comparable to the control harvest values. The investigations carried out on the wheat example demonstrated in principle the possibility of long-term functioning of the LSS photosynthesizing link based on optimizations of biological and physicochemical methods of utilization of the human and plants wastes. The possibilities for the use of these technologies for the creation integrated biological-physicochemical LSS with high closure degree of internal matter turnover are discussed in this paper.