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Advanced space life support systems, especially systems that include growing plants to produce food, require the recovery of resources - primarily carbon dioxide and water - from various hydrocarbon wastes. Supercritical water oxidation (SCWO) of wastes is one of several possible techniques for oxidizing waste organics to recover the carbon dioxide and water. Supercritical water oxidation has the advantages of fast kinetics, complete oxidation, and the minimization of undesirable side products. However, the SCWO process requires further development before the process can be implemented in space life systems. One of the SCWO development needs is in the area of destruction of insoluble solids - such as inedible biomass or human wastes. Insoluble solids have to be introduced into a SCWO reactor as particles, and it can be expected that the particle size of the solids will affect the rate of reaction.

For Supercritical Water Oxidation (SCWO), particle size is a key factor effecting requirements for feed preparation, slurry concentration and pumping, rate of reaction, and reactor size. To address these issues, an experimental research program was undertaken to evaluate the effect of particle size on the reaction kinetics in SCWO of solid particulates (wheat straw and cellulose particles in this case). The experiments also included evaluation of the effects of temperature, pressure, and agitation. Some corrosion data were obtained. A two-step reaction mechanism was revealed. Empirically based mathematical relationships were developed that can be used for SCWO system design.

A variety of techniques, including supercritical water oxidation, fluidized bed combustion, and microwave incineration have been applied to the destruction of solid wastes produced in regenerative life support systems supporting long duration manned missions. Among potential problems which still deserve attention are the need for operation in a variety of gravitational environments, and the requirement for improved methods of presenting concentrated solids to the reactor. Significant improvements in these areas are made possible through employment of the magnetically assisted gasification process. In this paper, magnetic methods are described for manipulating the degree of consolidation or fluidization of granular ferromagnetic media, for application in a gravity independent three step solid waste destruction process.

A Microwave Powered Solid Waste Stabilization and Water Recovery Prototype system has been developed for the treatment of solid waste materials generated during extended manned space missions. The system recovers water initially contained within wastes and stabilizes the residue with respect to microbial growth. Dry waste may then be safely stored or passed on to the next waste treatment process. Using microwave power, water present in the solid waste is selectively and rapidly heated. Liquid phase water flashes to steam and superheats. Hot water and steam formed in the interior of waste particles create an environment that is lethal to bacteria, yeasts, molds, and viruses. Steam contacts exposed surfaces and provides an effective thermal kill of microbes, in a manner similar to that of an autoclave. Volatilized water vapor is recovered by condensation.