Every year, each of us produces some 500 litres of urine and 50 kilograms of faeces a year, enough to fertilise plants that would produce more than 200 kilograms of cereals. Scale that up and the world's population excretes 70 million tonnes of nutrients annually. Applied to fields, this could replace almost 40 per cent of the 176 million tonnes of nutrients in chemical fertilisers used by the world's farmers in 2011.
In Bangalore, the so-called "honey-suckers" hoover up the city's sewage from a million septic tanks and pit latrines and head for farms outside the city, where their loads are in demand to fertilise vegetables and coconut and banana trees. The fact is that human sewage is packed with nitrogen, phosphorus and potassium compounds, the three main nutrients plants need to grow - helpfully in roughly the correct proportions.
Provided there are sufficient controls for hygiene, health and safety concerns can been dealt with. And on the up side, there are significant economic benefits. In one experiment, after just 13 weeks, corn cobs were about 15 times bigger than they would have been without being fertilised by urine. Besides this, a single truck driver can service a population of 20,000 people, and generate an income of $50,000 a year, twice the price of a new truck.
Source: New Scientist. Full article here.
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