Recycling urine to promote social change
A nitrification reactor in the Newlands Mashu field laboratory in Durban, South Africa © Kai Udert – Eawag
Rich in vital nutrients for agriculture, urine could go from being a waste product to a transformative and financially valuable raw material that could even help promote sanitation.
Once you get over the “yuck-factor,” you wonder why we let so much urine go to waste. Urine is rich in nitrogen, phosphorus, and potassium – crucial components in agricultural fertilizers. It is free and plentiful and yet rarely recycled. For the past 5 years, a team of researchers and town authorities has been developing a urine-recycling scheme in a South African municipality with the goal to transform urine into fertilizer and promote access to sanitation. EPFL scientists are involved in assessing the health safety aspect of the project and in particular the inactivation of pathogens in the processing steps. They published their findings in the journal Environmental Science: Water Research & Technology this month.
Currently, the scheme is being tested on a pilot level at eThekwini Water & Sanitation, which is the water utility of the municipality in Durban, South Africa. This is done as part of the VUNA project – short for “Valorization of Urine Nutrients in Africa” –, which was launched, by Eawag and eThekwini Water and Sanitation. Every week, municipal workers collect urine from some of the 90’000 urine-diverting dry toilets already installed in the region in a push to improve local access to sanitation. By making waste a tradable commodity, the project leaders hope to satisfy a number of aims in one fell swoop: recovering nutrients from urine to produce valuable fertilizer, promoting the use of installed dry toilets, and offsetting at least part of the initial investment made.
In the research that led up to the publication, Heather Bischel, from ENAC’s Environmental Chemistry Laboratory and the publication’s first author, investigated whether the fertilizer production process itself was enough to inactivate pathogens contained in urine. “Urine is often thought to be sterile, but because it is collected using urine-diverting dry toilets it can be contaminated by pathogens from feces, such as bacteria and viruses,” she says. Any initiative that seeks to scale up urine collection for fertilizer production must ensure that the process is safe for the workers handling it.
There are many ways to covert urine into liquid fertilizer. Here, the researchers focused on a process called “nitrification”, during which the odorous ammonia contained in urine is converted into the less volatile nitrate. Using bacteria and bacteria-infecting viruses called bacteriophages instead of the actual pathogens found in urine, Bischel and her co-authors showed that some of the microorganisms survived the nitrification process. They argue that a second, more expensive step would be required to fully neutralize them: distilling the nitrified urine.
In upcoming work, the ENAC researchers will try to determine which pathogens are commonly detected in urine in eThekwini, and they will perform a full risk-assessment of the urine collection, distribution, and processing steps.
More information about the project can be found at www.vuna.ch
This work is funded by the US National Science Foundation International Research Fellowship Program, the Swiss National Science Foundation, and the Bill and Melinda Gates Foundation and was carried out as part of the research project VUNA - Promoting sanitation and nutrient recovery through urine separation.