NOx Emission during Operation of a Drying Toilet System in Air-Circulated Confinement Experiment

The Closed Ecology Experiment Facilities (CEEF), designed to simulate material circulation, is an artificial closed agricultural ecosystem with plants, humans, and animals. The drying toilet system “DRI-LET^®” had been installed in the habitation module as a human waste processor for material circulation by carbonizing. Carbonizing of human waste has advantages in life support systems because it can minimize the total volume and weight of human waste. However, this toilet system releases many gases during processing. In particular, NO₂ concentration in the habitation module increased up to 4 ppm when one person used the toilet system. In this paper, we report NO and NO₂ behavior in the habitation module during experiments and a method to reduce their concentrations by using NO and NO₂ adsorbent.