Human urine and faeces as a fertilizer

By Ian Caldwell and Arno Rosemarin, Stockholm Environment Institute

Global prices for chemical fertilizer have risen dramatically over the last year, contributing to food price increases of 40 per cent according to the FAO Index. The surge in fertilizer prices has also made the practising of conventional agriculture increasingly difficult, especially for smallholder farmers in developing countries.

As a result of the rapid upward movement of prices there has been a growing interest in alternative sources of fertilisers involving recycling and reuse. One readily available replacement or supplement to conventional fertilizers, that has yet to be considered, is human urine and composted faeces.

Through the use of urine-diverting dry toilets, or ecosan toilet, urine and faeces can be collected separately and the end-products can be reused as complete fertilizers. This is a stable local source for households which have their own ecosan toilet. The urine and composted faeces can also be sold, creating local markets for fertilizer.

Humans produce roughly 500 litres of urine and 50 litres of faeces per person per year. These contain about 4 kg of nitrogen, 0.5 kg of phosphorous and 1 kg of potassium, the three basic elements for plant growth. The exact amount varies from region to region depending on food intake. Seventy per cent of the nutrients excreted by humans are in the urine fraction.

In Mauritania, which has a population of about 3 million, the excreta from the entire population is worth annually about EUR 25 million for the equivalent amount of chemical fertilizer. In addition, by producing fertilizer using ecological sanitation approaches, there are considerable savings on transportation, and human health and the environment are protected through proper containment, which is normally not the case for conventional sanitation in poor communities.

The use of urine and composted faeces for agricultural production is a key method of practising sustainable agriculture, improving local food security, and promoting better nutrition through increased food production.

 The potential for a market in urine – sold by the jerry can! (Photo: CREPA, Burkina Faso)

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