In 2002, the Bristol BioEnergy Centre’s team lead by Dr. Ieropoulos started working on “urine-tricity” or “pee power”. The project has developed since then, it is supported by several organisations, including the Bill and Melinda Gates Foundation, and it is in collaboration with the international NGO, Oxfam. The aim of « pee power » is to generate electricity thanks to a human waste, specifically urine.
Urine-tricity relies on a microbial fuel cell (MFC), which is an energy converter that drives an electric current by using bacterias. « The microbial fuel cells work by employing live microbes which feed on urine for their growth and maintenance » (Dr. Ieropoulos). So when urine flows through MFC, the microbes consume it for their own metabolism and then, they reject electrons that are converted into energy. The MFC is a tube, made with non-pollutants materials, with an electrode on the inside (negative side, called anode) and one on the outside (positive side, called cathode). There are live microbes inside the MFC : in the anode part, the microbes feed on the organic carbon components of the urine and then reject electrons onto the positive electrode (cathode) through their respiratory pathway : the reaction is completed, it leads to the production of electricity.
« This technology is as green as it gets, as we do not need to utilise fossil fuels and we are effectively using a waste product that will be in plentiful supply » (Dr. Ieropoulos). Indeed, people around the world produce around 6.4 trillion litres of urine per year ( The Economist) : urine is an unlimited resource and not only it is a waste used as a renewable energy, it also avoids water treatment costs due to urine. According to Eawag (the Swiss Federal Institute of Aquatic Science and Technology), urine makes up 1% of the total volume of waste water but it accounts for 50 to 80% of the nutrient content : therefore, there is a cost to removing these threatning contents. Furthermore, as coal and fossil fuels continue to increase greenhouse gases emissions, scientists are searching more renewable and sustainable ways to provide electricity : pee power could be one of them.
The concept of urine-tricity has been tested in several places. It was first employed at the University of the West of England. Then it has been used at the british festival of Glastonbury since 2015, mostly to charge mobile phones and for internal lightning, but in 2017, urine-tricity was used for something bigger : to power display boards at the festival. The urine comes out of the cubicles through a pipe and it goes straight to boxes where are stored the MFC : then the electricity is used to light up the toilets and power the information boards. In september 2017, pee power was introduced to the Sesame Girls School in Kisoro, Uganda. The electricity generated by the urine is used to enlighten the path to the toilets as well as the exterior of the bathroom building.
There are several aims to urine-tricity. First, it is a sustainable way to provide electricity, thanks to a renewable resource. Since that resource is urine, it is also a way to reduce waste by actually using it in an efficient way. But it also has a safety goal : in developping countries, as well as in refugee camps, most of the toilets are not lightened therefore it favors assaults at night. Using urine to enlighten the toilets is a way to provide electricity and safety, at a relatively low cost. Indeed, when urine-tricity was installed at the University of the West of England, the cost to set it up was around 600£ (= around 800$). However, if it was installed in a village of 2,500 inhabitants, the president of the International Society for Microbial Electrochemistry and Technology, Korneel Rabaey, says it would cost between 5,000 and 10,000$. While this cost is more important than solar panels for instance, this system would last much longer « because these organisms inside are self-renewing. As long as you feed it waste water, the bacteria is happy » (K. Rabaey). Therefore, this technology could provide electricity at a relatively low cost, while doing it in a sustainable way. At the same time it could be good for the economy : the cost is not that high if we take into account the fact that this technology would last a long time, and this technology avoids certain costs, such as treating water infected with urine.
By Alissia Leclerc