Yu.A. Kudenko

Mineralization of wastes of human vital activity and plants to be used in a Life Support System.

Available methods for mineralizing wastes of human activity and inedible biomass of plants used in this country and abroad are divided into two types: dry mineralization at high temperatures up to 1270 K with subsequent partial dissolution of the ash and the other--wet oxidation by acids. In this case mineralization is performed at a temperature of 470-460 K and a pressure of 220-270 atmospheres in pure oxygen with the output of mineral solution and dissoluble sediments in the form of scale. The drawback of the first method is the formation of dioxins, CO, SO2, NO2 and other toxic compounds. The latter method is too sophisticated and is presently confined to bench testing. The here proposed method to mineralize the wastes is in mid-position between the thermal and physical chemical methods. At a temperature of 80-90 degrees C the mixture was exposed to a controlled electromagnetic field at normal atmospheric pressure. The method merits simplicity, reliability, produces no dissoluble sediment or emissions noxious for human and plants. The basic difference from the above said methods is to employ as an oxidizer atomic oxygen, its active forms including OH-radicals with hydrogen peroxide as the source. Hydrogen peroxide can be produced with electric power from water inside the Life Support System (LSS).

Some Methods for Human Liquid and Solid Waste Utilization in Bioregenerative Life-Support Systems

Bioregenerative life-support systems (BLSS) are studied for developing the technology for a future biological life-support system for long-term manned space missions. Ways to utilize human liquid and solid wastes to increase the closure degree of BLSS were investigated. First, urine and faeces underwent oxidation by Kudenko’s physicochemical method. The products were then used for root nutrition of wheat grown by the soil-like substrate culture method. Two means of eliminating sodium chloride, introduced into the irrigation solution together with the products of urine oxidation, were investigated. The first was based on routine electrodialysis of irrigation water at the end of wheat vegetation. Dialysis eliminated about 50% of Na from the solution. This desalinization was performed for nine vegetations. The second method was new: after wheat cultivation, the irrigation solution and the solution obtained by washing the substrate containing mineral elements not absorbed by the plants were used to grow salt-tolerant Salicornia europaea L. plants (saltwort). The above-ground biomass of this plant can be used as a food, and roots can be added to the soil-like substrate. Four consecutive wheat and Salicornia vegetations were cultivated. As a result of this wheat and Salicornia cultivation process, the soil-like substrate salinization by NaCl were considerably decreased.

Electrosynthesis of hydrogen peroxide from oxygen in a gas-diffusion electrode in solutions of mineralized exometabolites

The electrosynthesis of H2O2 in aqueous solutions (pH 1–9) of mineralized liquid and solid bio-wastes (exometabolites) for their processing in closed life-support systems was studied. It was shown that H2O2 can be obtained in these solutions by electrochemical reduction of oxygen in carbon black gas diffuse electrodes to concentrations of over 2 M with current efficiency 80%. The composition of the solution was found to affect the accumulation of H2O2 during the synthesis. The solutions can be concentrated further to 19 M H2O2. The results showed that the electrolytic method is promising for preparing H2O2 for closed life-support systems.

Development of human exometabolite deep mineralization method for closed ecosystems.

Methods of physicochemical further oxidation of hardly soluble sediment obtained from “wet combustion” of human exometabolites applied to space-purpose Bio Technological Life Support Systems (BTLLS) were studied. Most hardly dissoluble sediment containing Ca, P, Mg, and other essential plant nutrition elements were shown to dissolve in H2O2 and HNO3 aqueous media activated by alternating electric current. Dissolved additional mineral elements allowed (as demonstrated for lettuce) to increase the productivity of BTLLS phototrophic unit plants more than twice, which is comparable to their productivity on standard Knop solution with balanced chemical composition. Thus, dissolved mineral elements can be involved into BTLLS turnover process and increase its closure degree.

Physicochemical conversion of human exometabolites for the NaCl involvement into the mass exchange in closed life support systems.

The results of the original physicochemical method of NaCl recovery out of the mineralized human metabolites’ solution obtained after their oxidation in H2O2 aqueous solution under the influence of alternating electric current are presented. The technological stages of the newly developed method are described, and its efficiency at each stage is demonstrated. The possibility to efficiency isolate Na from the NaHCO3 solution by applying electrodialysis technology and temperature separation is demonstrated. The HCl synthesis from Cl2 and H2 released during electrolysis is stable, allowing its combining with electrodialysis aimed at NaCl production under the conditions of a closed life support system.