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Since the mid 1980s, NASA has developed advanced waste management technologies that collect and process waste. These technologies include incineration, hydrothermal oxidation, pyrolysis, electrochemical oxidation, activated carbon production, brine dewatering, slurry bioreactor oxidation, composting, NOx control, compaction, and waste collection. Some of these technologies recover resources such as water, oxygen, nitrogen, carbon dioxide, carbon, fuels, and nutrients. Other technologies such as the Waste Collection System (WCS - the commode) collect waste for storage or processing. The need for waste processing varies greatly depending upon the mission scenario. This paper reviews the waste management technology development activities conducted by NASA since the mid 1980s and explores the drivers that determine the application of these technologies to future missions.

Pyrolysis processing of solid waste in space will inevitably lead to carbon formation as a primary pyrolysis product. The amount of carbon depends on the composition of the starting materials and the pyrolysis conditions (temperature, heating rate, residence time, pressure). Many paper and plastic materials produce almost no carbon residue upon pyrolysis, while most plant biomass materials or human wastes will yield up to 20-40 weight percent on a dry, as-received basis. In cases where carbon production is significant, it can be stored for later use to produce CO2 for plant growth. Alternatively it can be partly gasified by an oxidizing gas (e.g., CO2, H2O, O2) in order to produce activated carbon. Activated carbons have a unique capability of strongly absorbing a great variety of species, ranging from SO2 and NOx, trace organics, mercury, and other heavy metals.

Pyrolysis is a very versatile waste processing technology which can be tailored to produce a variety of solid liquid and/or gaseous products. The main disadvantages of pyrolysis processing are: (1) the product stream is more complex than for many of the alternative treatments; (2) the product gases cannot be vented directly into the cabin without further treatment because of the high CO concentrations. One possible solution is to combine a pyrolysis step with catalytic oxidation (combustion) of the effluent gases. This integration takes advantage of the best features of each process, which is insensitivity to product mix, no O2 consumption, and batch processing, in the case of pyrolysis, and simplicity of the product effluent stream in the case of oxidation. In addition, this hybrid process has the potential to result in a significant reduction in Equivalent System Mass (ESM) and system complexity.

NASA Ames Research Center and Lawrence Berkeley National lab have completed a three-year joint NRA research project on the use of waste biomass to make a gaseous contaminant removal system. The objective of the research was to produce activated carbon from life support wastes and to use the activated carbon to adsorb and remove incineration flue gas contaminants such as NOx. Inedible biomass waste from food production was the primary waste considered for conversion to activated carbon. Previous research at NASA Ames has demonstrated the adsorption of both NOx and SO2 on activated carbon made from biomass and the subsequent conversion of adsorbed NOx to nitrogen and SO2 to sulfur. This paper presents the results testing the whole process system consisting of making, using, and regenerating activated carbon with relevant feed from an actual incinerator. Factors regarding carbon preparation, adsorption and regeneration are addressed.

In this paper we have developed a unique approach to providing the elements required for crop production in a steady-state condition, which is essential for Space habitats. The approach takes into consideration human elemental requirements and crop requirements for healthy growth and develops a method for the calculation of the rates of nutrient uptake for the different elements for different crops. The uptake rates can be used to calculate the rate of nutrient supply required in the hydroponic solution. This approach ensures that crops produced will not have excessive levels of elements that may be harmful to humans. It also provides an opportunity to optimize the processes of crop production and waste processing through highly controlled feed rates.

This paper presents the results from a joint research initiative between NASA Ames Research Center and Lawrence Berkeley National lab. The objective of the research is to produce activated carbon from life support wastes and to use the activated carbon to adsorb and chemically reduce the NOx and SO2 contained in incinerator flue gas. Inedible biomass waste from food production is the primary waste considered for conversion to activated carbon. Results to date show adsorption of both NOx and SO2 in activated carbon made from biomass. Conversion of adsorbed NOx to nitrogen has also been observed.

Terraforming of Mars is the long-term goal of colonization of Mars. However, this process is likely to be a very slow process and conservative estimates involving a synergetic, technocentric approach suggest that it may take around 10,000 years before the planet can be parallel to that of Earth and where humans can live in open systems (Fogg, 1995). Hence, for the foreseeable future, any missions will require habitation within small confined habitats with high biomass to atmospheric mass ratios, thereby requiring that all wastes be recycled. Processing of the wastes will ensure predictability and reliability of the ecosystem and reduce resupply logistics. Solid wastes, though smaller in volume and mass than the liquid wastes, contain more than 90% of the essential elements required by humans and plants.