Global study of 48 cities finds nature sanitizes 41.7 million tons of human waste a year

Researchers found that nature provides at least 18% of sanitation services in 48 cities worldwide, according to researchers in the United Kingdom and India. The study estimates that more than 2 million cubic meters of the cities' human waste is processed each year without engineered infrastructure. This includes pit latrine waste that gradually filters through the soil -- a natural process that cleans it before it reaches groundwater.