As the sun dips below the horizon and darkness descends over Durban, a small corner of the city is illuminated by the glow of “uricity”, a novel source of green electricity developed by a team of English university researchers.
Also known as Pee Power, this is biological electricity tapped from human urine.
So far, only small volumes of uricity are being generated at the Durban prototype plant, but it’s enough to light up a communal ablution block for several hours each night in a dense shack settlement of nearly 2 500 people.
The Pee Power mini plant, developed at the University of the West of England (UWE Bristol), forms part of a wider global project to reinvent toilets, reduce water pollution and transform notions about human “waste” by turning it into more valuable products such as fuel and fertiliser.
Over recent decades, Durban has become something of a test bed for several research collaborations for water-saving in sanitation by the eThekwini Municipality, the Bill & Melinda Gates Foundation, the South African Water Research Commission, the University of KwaZulu-Natal and several overseas universities.
Putting waste to work
Quite apart from producing electricity, the developers of the UWE Pee Power technology also hope it can one day help to purify some of the vast volumes of chemically and biologically polluted wastewater that pour daily into rivers across the world.
The Durban plant somewhat resembles a bank of normal lead-acid batteries, each with anodes and cathodes. But in fact, this is a microbial fuel cell, says Ioannis Ieropoulos, director of the Bristol BioEnergy Centre and creator of the technology.
“A microbial fuel cell is a device which produces electricity from the natural process of biodegradation,” Ieropoulos explained in an interview. “Bacteria inside the device consume organic matter [as food] and electricity is produced as a by-product of their anaerobic respiration.
“Although microbial fuel cells seem similar to batteries – what with a negative terminal and a positive terminal, and electrons flowing from the former to the latter – the main difference is that these fuel cells will never run out for as long as fuel (ie waste) is provided.”
The plant, installed in a shack settlement in the Greenwood Park area of Durban last year, has been operating for about nine months – hooked up to the back end of a communal toilet block to collect a steady stream of urine from male urinal stands.
Ieropoulos says the original idea for microbial fuel cells dates back to a discovery in 1910 by Michael Cressé Potter, a professor of botanology at Durham University, in a paper he published which described how electricity could be produced using cell cultures of bacteria and sugar.
“The origins of ‘biological electricity’ go back even further to the 18th century in Luigi Galvani’s work on frog legs and the movement of tissue and muscle with electricity,” says Ieropoulos, who launched a more advanced microbial fuel cell project for his PhD thesis at UWE Bristol in 2002.
Flowing from his research project and subsequent development work, the university announced plans in November 2018 to start scaling up the technology to generate commercial volumes of uricity.
Funded by the Bill & Melinda Gates Foundation, the UK’s Engineering and Physical Sciences Research Council (EPSRC) and the EU, the Pee Power technology has been successfully trialled at the Glastonbury Festival and at two schools in Kenya and Uganda with limited access to mains electricity.
“The long-term objective is to generate large amounts of electricity,” says Ieropoulos, “At the moment the fuel cells are limited by lab-scale prototype designs but their true potential can only be revealed with scaled-up mass manufacturing.”
One of the aims of the Durban project is to reduce the size of previous prototype plants that were trialled in East Africa and Glastonbury, to increase the power output and also improve the peripheral electronics hardware for better interfacing with applications such as LED lights, smart e-ink displays, mobile phones or microprocessors.
Toilet power in the future
Beyond the current small-scale use in informal settlements or remote areas, Ieropoulos sees potential for much wider and larger-scale application in the future.
“Our approach for optimisation has been to downsize individual fuel cells and then multiply them in modules and stacks … We are envisaging a future where microbial fuel cells are deployed widely in both the developing and developed worlds, offering the benefit of free electricity and a way of cleaning wastewater before it reaches the environment.
“Microbial fuel cells do not just run on urine – urine is just one example of a fuel that can be converted to electricity. But, as previous and ongoing work has demonstrated, anything organic that can flow into a fuel cell can be broken down by the microbes and converted into electricity.”
As a result, microbial fuel cells could be expanded to produce electricity from major wastewater treatment works, with the spent effluent collected as a by-product to produce commercial fertilisers.
Ordinary home owners could also integrate the fuel cells into their back garden or compost heaps, for off-grid wastewater treatment and electricity generation.
This also ties in with local research initiatives led by Chris Buckley, co-head of the Pollution Research Group at the University of KwaZulu-Natal.
For several years, Buckley’s group has been working with the eThekwini Municipality and the Water Research Commission to examine the feasibility of extracting commercial fertilisers from large wastewater treatment works; separating urine and faeces through the development of urine-diversion toilets and by redesigning toilet pedestals to reduce the volume of water that is wasted from flushing.
As part of the Bill & Melinda Gates Foundation “Reinvent the Toilet Challenge”, Buckley’s Pollution Research Group is currently testing 19 new toilet pedestal designs, including an advanced urine-diversion toilet pedestal designed by the Austrian-based EOOS Design Studios.
“Bear in mind that about 35% of the water used in most households gets flushed down the loo. With modern technology and re-engineering, it is possible to redesign toilet pedestals to use as little as 1.5 litres to flush away faeces – compared to the 10 litres used in some of the older chain-pull toilet cisterns,” said Buckley.
“In a water-scarce country like South Africa we need to keep squeezing down the volume of water that is wasted on toilet flushing.”