Urine is a resource.
Photo: © India Water Portal/Flickr.com

How to exploit urinals for cheap fertiliser

Recycling urine collected at public toilets is a cheap and simple way to produce fertiliser, according to the developer of a waterless urinal at Indian Technology Institute.

Human urine contains three nutrients – phosphorus, nitrogen and potassium – that are essential for plant growth, says Vijayaraghavan Chariar, a researcher at the Indian Institute of Technology, New Delhi. Every individual produces four to five kilogrammes of these nutrients in their urine annually, explains Chariar, with this valuable material lost through what he calls modern "flush and forget" sanitation systems that often end up polluting waterways.

"Urine is a resource," Chariar says. "If it can be separated in restrooms whenever possible – definitely in public institutions and other public places – then we can easily recycle it. But it takes more energy and effort to recover these nutrients once the urine is mixed up with other matter in sewage systems."

According to the scientist, waterless urinals already exist, but current designs often require the frequent replacement of odour-preventing cartridges, making maintenance a prohibitive cost, despite potential savings through lower water use. "What we have come up with are urinals for the developing world," he says. "These are products that use no chemicals. Nothing would need to be replaced for three years, if not longer."

Since the urinals were put on sale in May 2013 through Ekam Eco Solutions, the company Chariar founded to market his innovation, about 4,000 units have been installed in India. His prefabricated Waterless Public Urinal Kiosks store urine in tanks and use a patented cartridge to stop the smelly gases escaping. This eliminates the need for fresh water to flush away the urine, he explains. According to the company's website, the cartridge uses a ball valve to trap the gasses, whereas other models use membranes or liquid sealants that gradually degrade and need replacing. For "high-volume" urinals in public places, each urinal can save 155,000 litres of fresh water a year, he adds.


Chariar laments that so far there has been little interest in using the design's potential to harvest urine, with nearly all of the urine being disposed of through traditional sewage systems. He puts this down partly to politicians thinking that the cost of transporting urine would be prohibitive. Yet he notes that simply adding magnesium chloride to urine and adjusting its acidity will lead to a phosphate mineral called struvite forming. This can be filtered out from the bulk liquid, and it would be much lighter, easier and cheaper to transport to rural areas, Chariar says.



Ekam Eco Solutions works in the domains of Sustainable Sanitation, Value-added Bamboo Products and Sustainable Livelihoods. 

In the domain of Sustainable Sanitation, the objective of Ekam Eco Solutions is to design, develop and disseminate safe, sustainable and culturally appropriate sanitation solutions so that communities experience better health and abundance of pure water bodies is restored. Access to safe and sustainable sanitation for every denizen of the planet is one of the Millennium Development Goals (MDGs). Ekam’s approach to sanitation recognises the opportunity to provide waterless urinals, source-separation toilets and nutrient recovery reactors with the additional feature of making every effort to break the pathogen cycle and close the nutrient cycle.




More information:

Website Ekam Eco Solutions

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