Background on Biofuel Cells

Biosensors and Bioelectronics, Volume 22, issue 7 (February 15, 2007), p. 1224-1235

With all the hype about biofuel cells and their huge potential in the future, I wanted to dig deeper and understand more about it.  In this scientific review article, they talk about the history, the recent advances, and its multiple applications as of 2006.  Biofuel cells are based on the concept that if an electrical action can induce a biological reaction, then the vice versa must be true.

It seems there are several different classes of biofuel cells.

1. Using organic waste(such as corn husk) to generate secondary fuel (such as hydrogen or ethanol)

Pro: consumes waste and gives electrical power.   Con: not a direct generation of power

2. Using  micro-organisms or enzymes to convert chemical fuel into electricity

      There are two electrodes in a solution in the fuel cell. When a fuel is introduced into the cell, it is oxidized at the anode.  The released electrons are then used to reduce O2 at the cathode. Use of enzymes help the process of glucose reduction to CO2.  Enzymes have great efficiency but they don’t help in the transfer of the released electrons to the electrode. Microbes are better than enzymes in oxidizing many biofuels and is less susceptible to poisoning. The drawback is that it’s hard to export the generated electrons out of the microbes for use in the fuel cell.  But these can be overcome with mediators.

      3. Hybrid cells that combine photochemistry and biological systems

        Some micro-organisms can capture light as part of their respiration process and convert this into electrical energy.

        Conventional fuel cells use hydrogen or methanol, but they introduce storage and transport problems as they are gases.  Therefore, exploring these classes of biofuel cells in depth can solve these problems.  Some  of its possible applications could be in transportation, implantable devices in living systems, wastewater treatment, and in robots.  One calculation showed that 1 litre (0.264 gallon) of concentrated carbohydrates could power a car for 25-30km (15-19mi), which means that a 50L(13gal)  tank can generate power for 1000km (621mi).


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