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Experiments in Urine Reuse for Agriculture

WaterAid has been promoting ecological sanitation through composting toilets that separate faeces for compost and urine on vegetable gardens by diluting it with water

Re-using nutrients from urine would make a lot of sense, and there are several active research projects on that topic, many of which are just as energy-intensive and therefore expensive as traditional production methods. At WaterAid, we wanted to find solutions that would be typically affordable and make sense for farmers in sub-Saharan Africa.

Gold in Mozambique

In Mozambique, WaterAid has been promoting ecological sanitation for some time, through composting toilets that separate faeces for compost and urine. With composting toilets, urine is typically left to infiltrate in the ground and can create unpleasant smells, which is a common reason for not using them. But a recent project has been transforming behaviours in peri-urban Maputo to promote the direct reuse of urine on vegetable gardens by diluting it with water.

Solar heating experiments in the UK

One limitation mentioned by the project participant in the film is the low volume that can be used, limiting this application to relatively small gardens. We wondered if another way was possible, so we ran a competition in 2013 together with the Society of Public Health Engineers. The winners suggested a solar heating system that could pasteurise urine, evaporate water and allow urea to be extracted and reused as fertiliser. After a trip to Tanzania to test the feasibility, young engineer Paul Foulds worked hard to develop a prototype.

He managed to extract urea (despite solar heating being much less efficient in the UK), but ran into issues with keeping the urea dry. We therefore worked with students in Water and Environment at Cranfield University, who, after a few months of testing different setups and evaporation methods, managed to extract urea. The urea was in very small quantities, which seemingly indicated that this wouldn't be a commercially viable method. However, the students have some ideas that could help the process, which we could continue testing in the future.

Source: WaterAid

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