Updated: May 19, 2020
Fuel cells have grown to take an increasingly central place in the green power supply scene. Indeed, the idea that we can produce energy from naturally occurring hydrogen, creating virtually no pollution as the only by-product of the reaction is water, is of particular interest to many environmentally aware businesses. However, while the idea appeared in 1838, fuel cells don’t seem to be commercially available for large-scale production just yet. This begs the question is fuel cell technology genuinely revolutionary or is the principle just a scientific fad? To answer this question, we must first understand what a fuel cell is and how it works. A fuel cell is a device producing electricity as a result of a chemical reaction between hydrogen atoms and an anode which strips them of their electrons. The answer results in free electrons being transported through wires and positively charged hydrogen ions being transported through the electrolyte. The transport of negatively charged electrons through the wires produces direct current. At the exhaust, the ionised hydrogen combines with the oxygen present in the air and the electrons thus creating water. The fuel cell will, therefore, produce electricity as long as it is supplied with oxygen and hydrogen. In other words, a fuel cell is a battery that produces electricity with hydrogen and oxygen without creating any pollution. So why is such a great technology limited to supplying power to small remote scientific instruments or vessel power production at most? What barriers prevent it from genuinely up-scaling? The United States Department of Energy is currently focusing its R&D on three critical barriers to up-scaling: cost, performance and durability. Indeed, to achieve a higher output of power, the reaction that takes place between oxygen and hydrogen needs to be accelerated at the cathode. That’s why platinum compounds are used as catalysts to the response. Platinum being extremely costly, the up-scaling process would require such an investment that a fuel cell large enough to produce power on a national scale, or even a city-wide scale would not be profitable. Further, the electrodes degrade over-time affecting the performance of energy production of the fuel cell. The durability target being between 40 000 hours and 50 000 hours, a lot of R&D work is needed to achieve these targets. To meet these objectives, different designs have been theorised and tested, each with its strong points and weaknesses, varying from purity requirements of the fuel to running temperatures and cost-effectiveness. However, one type of fuel cell would go even further than the production of electricity without pollution. Indeed, Bioelectrochemical systems (BES) would produce valuable products such as energy or costly chemicals (e.g. hydrogen) not only without producing harmful by-products but also by treating man-made waste-water. They use the same principle as electrochemical fuel cells described earlier, however, in BES, specialised organisms (typically bacteria) are used to break down organic compounds at the anode under anaerobic (without oxygen) conditions. The energy produced is a by-product of the breakdown process. The European Commission Science for Environment Policy recognises this technology as a potential answer to the growing demand in energy and waste-water production in Europe in the coming years. A pilot plant was realised in 2012 in the UK where a 100-litre reactor managed to produce 1 litre of pure hydrogen per day on average. The reactor was designed in such a way that the combination of the energy present in the waste-water and additional input to the plant resulted in the production of pure hydrogen. The product mentioned above translates a 70% energy efficiency combining the input of energy to the reactor and the waste-water energy, however, with an improved design, the plant should be able to recover 100% of that energy, therefore attaining a break-even point of “free” treatment. However, it is to be mentioned that this prototype plant built with the cheapest material available had an energy cost of processing which was lower than a conventional waste-water treatment plant and removed comparable amounts of organic matter. Fuel cells are, therefore, a true potential breakthrough in their real-world application. They are a likely answer to two growing global concerns: waste-water treatment and energy production. However, the technology is too advanced for its time as the engineering required to upscale it and guarantee cheap, reliable and performant fuel cells is lacking. It is predicted though that it could close the gap in the next five to ten years allowing most countries to respond to their energy needs in the greenest way possible: by eliminating their… eliminations.