Dr Ioannis Ieropoulos inside the Bioenergy laboratory at the BRL, holding a phone powered by a microbial fuel cell stack. (c) Bristol University

Engineers at Bristol University have developed a microbial fuel cell (MFC) that turns organic matter, in our case urine, into electricity. The fuel cell is equipped on a mobile charger, and its creators envision the device being implemented in various other applications that can recycle urine. Restaurants, bars and various other buildings that employ public toilets might collect the urine in special containers which could then be converted into useful energy.

The MFCs work by breaking down the urine through the specially-grown bacteria’s metabolic process. The bacteria produce electrons as they consume the matter and it this natural process that creates a small electrical charge to be stored in the MFC.

“No one has harnessed power from urine to do this so it’s an exciting discovery,” said Dr Ioannis Ieropoulos, an engineer at the Bristol Robotics Laboratory where the fuel cells were developed.

“The beauty of this fuel source is that we are not relying on the erratic nature of the wind or the sun; we are actually reusing waste to create energy. One product that we can be sure of an unending supply is our own urine.”

Now, I don’t mean to discredit Dr. Ieropoulos, however a few years ago I’ve written about a similar full cell that converts the chemical energy in urea (found in urine) into electricity through an electrochemical process that does not require combustion, with heat as the by-product. True however, that particular system was not based on bacteria.

The electrons are then stored into a capacitor, whose electrical charge can be released to power a device. In this case, the Bristol researchers simply plugged in a commercial Samsung phone charger and were able to charge up the handset. Don’t get too excited yet, though. Their set-up is still an experimental prototype and so far the hurdles far outweigh the benefits. For one, its the size of a car battery and the handheld they charged only lasted for roughly the time it took to make a call.

Even so, the researchers are confident they can miniaturize their MFCs, and considering each fuel cell only costs around £1 to produce such devices could provide a new, cheaper way of generating power.

“One [use] would be to put these into domestic situations or it could be used in remote regions of the developing world,” said Dr Ieropoulos.

“The fuel cells we have used to charge a mobile phone with hold around 50ml of urine but the smallest we have had working in the laboratory hold 1ml, so we can make them a lot smaller. Our aim is to have something that can be carried around easily.”

“The concept has been tested and it works – it’s now for us to develop and refine the process so that we can develop MFCs to fully charge a battery.”