Introducing VUNA – recovering nutrients from urine to promote sustainable sanitation
To extract as much value as we can from waste, we recently launched a pilot to recover nutrients from urine to create nitrogen-rich liquid fertilizer. Urine constitutes about half of the waste we collect and remove from slums, and we are trying to maximize its potential as a feedstock for our end-products. At the same time, expanding our line of end-products offers farmers a greater selection of sustainable, domestically produced agricultural inputs. Farmers like using liquid fertilizers because they are easy to apply and are efficiently absorbed by plants, thereby quickly delivering nutrients they need to grow.
To help set up our urine-conversion work, we have partnered with a range of experienced organizations, including EAWAG, a Swiss water research institute, and the Pollution Research Group, in the department of chemical engineering at the University of Kwa Zulu-Natal in Durban, South Africa. We are piloting a system called “VUNA” that Eawag developed for urine valorization. VUNA is an acronym for ‘Valorization of Urine Nutrients in Africa,’ and the word also means ‘harvest’ in isiZulu and Swahili. Using urine treatment and nutrient recovery reactors to nitrify and distill urine, the pilot’s main aim is to retrieve nutrients, particularly nitrogen and convert them to liquid fertilizer.
Consultant Khonzaphi Dube, a chemical engineer and specialist in urine treatment, helped our team design our urine treatment facility, acquire the necessary equipment for its launch, and kick-start our VUNA pilot.
“I have always been passionate about providing sanitation solutions for cities with limited options, and over the years, I have pursued urine treatment projects with a focus on measuring the chemical and physical properties of urine to inform the ideal design, equipment and process for urine treatment. These insights and data I have collated have helped in developing efficient urine treatment prototypes. I am excited to be part of the VUNA launch at Sanergy!” says Khonzaphi.
With assistance from our research and development team, Khonza was tasked with setting up and running the VUNA reactor, which, as it turns out, was not an easy job.
“Most of the equipment needed for the reactor is not locally available; these were procured from Durban and Zurich. In addition, to get the reactor working, we needed activated sludge – a solution containing nitrifying bacteria – which was not available in Nairobi. To meet this need, we devised our own method of culturing the nitrifying bacteria from the Evergrow compost for the reactor,” he says.
The VUNA reactor has been running for 5 months now. The trial will continue for a few more months, after which we will have the results necessary to scale production.
“We are also testing the reactor using effluent from our biogas digesters, and by the end of the year, if all goes well, we will obtain enough experimental data to be able to design an industrial-sized plant that will treat 5 cubic meters of urine and 3 cubic meters of digestate per day,” Khonza says.
This is the first time VUNA technology has been tested using biogas effluent; neither the technology in Switzerland or South Africa has been used to process this type of feedstock.
Ultimately, we look forward to making available a liquid fertilizer for Kenyan farmers. Congratulations to Khonza and our R&D team for a job well done this far!