Biofuel Cells

As our society progresses, our population will continue to grow and technology use will continue to increase. More people and technology will force us to use more and more energy. The issue is that most of our energy, approximately 85%, comes from fossil fuel, coal, oil, natural gas, etc. has limited reserves and won’t last forever. Furthermore, the carbon emission created from these energy sources is one of the most significant contributors to climate change. As a result, sustainable energy that doesn’t leave a carbon footprint needs to be incorporated into our energy sources. Most people know solar power, which uses power from the sun, wind turbines, which use the energy from winds to generate energy, and electrically powered engines. A much less known source of energy that holds a lot of promise is microbiological fuel cells, better known as biofuel cells.

To understand how biofuel cells work, it's important to understand this type of energy. Most of the energy in our society is used to create electricity. Electricity is the flow of electric power, often in the form of electrons. Large power plants burn coal or gasoline to create steam to spin turbines at high speeds using the pressure of the gas. The turbines have magnets attached to them to repel electron wires and push them along to create a flow of electrons, thus producing electricity. Though this method is highly effective at producing electricity, the steam byproduct of gas created from the coal and oil generates billions of metric tons of carbon dioxide each year, and the reserves and oil and coal are limited on Earth.

Biofuel cells are promising as they can create the flow of electrons without burning fuels or coal. Biofuel cells work very similarly to batteries in that they utilize anodes and cathodes. An organic compound is attached to an anode, which is an electrode that oxidizes the organic material. For instance, if we used sugar as the organic compound, which is 𝐶6𝐻12𝑂6, we could oxidize it using water to obtain 𝐶𝑂2 , 24 𝐻+ atoms, and 24 electrons. The 𝐻+ would go into the solution of water because it is aqueous, therefore not being a part of the anode anymore. There is then a wire that connects the anode to the cathode, which is in the same solution as the water. The cathode does the opposite of the anode in that it reduces, or adds electrons, to a compound. If we continue with the sugar example, in this case, we could use oxygen from the air, the 𝐻+ ions in the solution, and the electrons to create a reaction that creates water. In that process, the electrons flowing through the wire to be a part of the reduction reaction will create electricity.

If some things aren’t adding up to you, that makes sense. You may be asking why the electrons can’t also just enter the solution and go directly to the cathode as the hydrogen ions did. That is because between the anode and cathode lies a semipermeable membrane. This is a barrier that allows certain molecules to pass through it while not allowing others. In our example, the hydrogen atoms can flow toward the cathode through the solution, but since the electrons cannot pass through a semipermeable membrane, they must travel through the wire.

Another question might be how is this any better than batteries. Well, unlike batteries which cannot be used after their chemicals have been depleted, biofuel cells work as long as the waste is replenished and can be added to anytime. Additionally, we haven’t discussed much as to what exact substances can be used to power biofuel cells. The amazing thing is that we can use waste. Thus, not only do biofuel cells not harm the environment, but they also aid in minimizing the waste we use. Substances like E. Coli, for example, can be used as biofuel cells. Furthermore, cells like these have been shown to output a much higher capacity of energy. A study performed by Frank Davis and Séamus P.J.Higson in 2006 found that 50 Liters, around the average size of a fuel tank in a car, that utilizes E. Coli and concentrated carbohydrates can fuel a car for almost 1000 km, or around 600 miles, far surpassing any battery powered car while utilizing waste as fuel.

The applications for biofuel cells don’t stop there. For instance, they are perfect for powering medical devices that are implanted in people. Instead of using batteries that need to be replaced or attached to a wire, medical devices can be powered using organic compounds like glucose in our bodies. Another application is to decrease water waste. As discussed, waste can be used as a fuel cell to create power. Using water waste would not only generate electricity in an environmentally friendly way, but it would also remove waste found in water masses.

You may be asking yourself why we aren’t using biofuel cells in our current world. The catch is that much of what has been said is the theoretical uses of these fuel cells, and our advancements up to this point haven’t made biofuel cells applicable at this point in time. The power output of most biofuel cells is extremely low compared to batteries. This is because there is no direct way to completely oxidize compounds. Enzymes can be used to fully complete oxidation processes like these, however. For instance, methanol can be completely oxidized using just 2 enzymes, however, even then, the process is relatively slow and, according to the same study done by Frank Davis and Séamus P.J.Higson in 2006, found that 2 microwatts per square centimeter were produced compared to the average lithium battery that generates 30 microwatts per square centimeter.

Biofuel cells have a long way to go in terms of increasing the power output of their electrical current to be used. However, research has been promising and progress has definitely been made to increase the power production of biofuel cells. The application that is nearest in sight is using biofuel cells to power medical devices, and the only holdback right now is that the enzymes needed to oxidize the fuel cells have life spans of only a few weeks, whereas they need to last years for them to be more useful than batteries. Genetic engineering of enzymes might be needed to increase their lifespan that much. One thing for sure is that scientists are committed to finding and putting these fuel cells to use, and the progress so far provides real hope for the future of sustainable energy.