Composting toilets use the natural processes of decomposition and evaporation to recycle human waste. Waste entering the toilets is over 90% water, which is evaporated and carried back to the atmosphere through the vent system. ... Ensure that the finished compost is safe and easy to handle.

We are raised with the idea that toilets smell bad. However, due to constant negative pressure inside the unit, a Sun-Mar composting toilet never smells. Compost must be mismanaged significantly or venting installed incorrectly in order for it not to operate odor-free.

In a composting toilet feces and toilet paper compost with a "bulking agent" like sawdust cover the poop to create air gaps for aerobic bacteria to break down the material.