1 Anaerobic Digestion for Reduction and Stabilization of Organic Solid Waste During Space Missions: Systems Analysis Qiyong Xu and Tim Townsend Environmental Engineering &. Science University of Florida David Chynoweth, Patrick Haley, John Owens, and Elana Rich Agricultural and Biological. Engineering University of Florida Sabrina Maxwell Boeing Hong-Lim Choi Animal Science and Technology Seoul National University ABSTRACT High Solids Leachbed Anaerobic Digestion (HSLAD) is a biological waste treatment system that has been successfully demonstrated for solid waste treatment in terrestrial applications. The process involves a solid phase leachbed fermentation, employing leachate recycle between new and mature reactors for inoculation, wetting, and removal of volatile organic acids during startup. HSLAD also offers a potential option for treatment of biodegradable waste on long-duration space mission and for permanent planetary bases and would produce 1.5 kg of methane, 4.1 kg of carbon dioxide and 1.9 kg of compost daily from 7.5kg of biodegradable solid wastes generated daily from a crew of six. HSLAD can operate at low temperature and pressure and has the potential for being a net energy producer. A detailed analysis of this process was conducted to design the system size required for a space mission with a 6-person crew The mass, energy and water balance of the process and an equivalent system mass (ESM) analysis are presented. INTRODUCTION One of the prerequisites to a successful long duration space mission is the efficient and safe treatment of the waste produced by the crew. The waste stream not only can be deleterious to the crew because of the existence of pathogens or the concentration of toxic substances, but also includes many resources (water, nutrients, etc.) vital to the life support of the crew. So, the purpose of treating waste includes the reduction of waste mass, volume, odor, and toxic materials and the regeneration of inorganic nutrients. Because of the resupply constraints in long duration missions, waste treatment and recycle become a critical component to future long duration space missions. In general, solid waste treatment includes collection, size reduction, conversion, and post-treatment. Processing technologies can be further divided into pre- and post-processing (PPP), and physicochemical (PC) and biological primary processing [14]. PPP processes are used to separate and size reduction waste, reduce volume, prepare for primary processing system and further refine products. Some PC processes, including incineration, electrochemical oxidation, thermal destruction and pyrolysis can deal with most solid waste stream components and can accommodate very high feed rates, converting the wastes almost entirely to end products [1]. However, PC techniques often require significant power and heat rejection capabilities. Thus, as has been pointed out by numerous authors, PC is expected to be most suitable for intermediate durations (up to several years)[7], not for long duration