Composting toilets a misnomer: Excessive ammonia from urine inhibits microbial activity yet is insufficient in sanitizing the end-product

► End-product from sixteen public composting toilets was analyzed. ► Maturity and sanitation were mutually exclusive goals. ► Inhibitor effects of NH3 dominated over TS%, temperature, or material age. ► Free [NH3] above 386 mg/kg NH3-N appears to inhibit nitrification. ► Despite naturally high [NH3], levels were inadequate to reliable eliminate Escherichia coli.