A waterless dry toilet, which generally costs about $2,000, collects human urine and feces and requires emptying by humans on a regular basis. Advocates claim the resulting matter can then be composted and used as fertilizer for food crops...

Warnberg's website explains that the dry toilets need to be emptied at 6- to 12-month intervals, "depending on loading," and his design includes the use of earthworms to "provide mixing and aeration."