Design and operation of an anaerobic digester for waste management and fuel generation during long term lunar mission

• We use high-solids anaerobic digestion for long term space missions.
• The unmixed digester performed better than the agitated digester.
• Evaluate appropriate process design for anaerobically digesting lunar mission waste.
• Prototype digester was designed and sized for four-person crew for 1 year mission.

Waste treatment and management for manned long term exploratory missions to moon will be a challenge due to longer mission duration. The present study investigated appropriate digester technologies that could be used on the base. The effect of stirring, operation temperature, organic loading rate and reactor design on the methane production rate and methane yield was studied. For the same duration of digestion, the unmixed digester produced 20–50% more methane than mixed system. Two-stage design which separated the soluble components from the solids and treated them separately had more rapid kinetics than one stage system, producing the target methane potential in one-half the retention time than the one stage system. The two stage system degraded 6% more solids than the single stage system. The two stage design formed the basis of a prototype digester sized for a four-person crew during one year exploratory lunar mission.