Bioelectricity is the electricity produced by electrochemically active bacteria as a result of their metabolic activities; harnessing bioelectricity is a clean way to obtain energy.
The climate crisis is a hot topic, as Greta Thunberg and weekly extreme weather events keep reminding us. The world’s population is rising, and with it, the demands of the people. Earth’s dire situation is a daily topic around the globe. The common consensus is that greed and fossil fuel consumption are the driving factors.
The need of the hour is cleaner, more sustainable ways of producing the energy we require. I mean, sure, alternative approaches are on the up-swing, such as solar, wind, hydroelectric, and geothermal energy, but these have their limitations, in that they are site-specific. A hydroelectric dam needs fast-moving water, solar panels need strong sunlight and windmills need flat, open land.
What if there was a site-independent way to generate electricity? Similar to how coal is burned to produce electricity, could we use our waste to create electricity? If so, how? Just put electricity-producing bacteria on the job!
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What is bioelectricity?
Bioelectricity is the electricity produced by living organisms such as bacteria, algae or fungi. When given a tasty food source—anything from wasted food to wood—to feed on, and they will produce small amounts of electricity as a result of their metabolic activities.
The term bioelectricity isn’t new. It was first used in the 1780s by Luigi Galvani, when he electrocuted a poor frog with lightning to see if its muscles would twitch, which they did. Since then, biologists have been fascinated by how life creates and puts electricity to use. You can read the full fascinating story behind that here.
Recently though, bioelectricity has been employed more often to describe the electricity that smaller life forms like bacteria produce, and that we can put to productive use.
We can generate this energy for ourselves by putting the bacteria in batteries. The biochemical reactions that generate bioelectricity occur in a particular setup within the battery containing two electrodes, organic matter (the substrate) and the microorganisms. This set up is called a Microbial Fuel Cell (MFC).
What are MFCs?
An MFC is a kind of fuel cell, similar to the one used to power Arnold Schwarzenegger in Terminator 3.
An MFC functions similar to a conventional battery. They both have a positive section with a positive electrode (anode) and a negative section with a negative electrode (cathode). Electrons generated in the positive section are picked up at the anode, and their journey across to the cathode generates the electric current.
The difference between an MFC and a fuel cell is that fuel cells produce electricity via a chemical reaction, whereas an MFC produces electricity via a biological process.
The bacteria are present in the anode (positive). When healthily supplied with food, they will release electrons, which are picked up by the anode. Now, there are more electrons at the anode than at the cathode, so the electrons will zip towards the cathode. The oxygen, protons and electrons react at the cathode (negative). This flow of protons and electrons creates a potential difference between the two electrodes, leading to the generation of bioelectricity.
What kind of microorganisms are used in MFCs?
The scientific name for the bacteria is Electrochemically Active Microorganisms (EAMs). What this means is that they can convert chemical energy, the energy in food, to electrical energy, the energy from electrons in a battery. To get them to work their chemical-to-electric magic, they need an oxygen-free environment (anaerobic), since oxygen will keep snatching the electrons away.
Not all EAMs are good bacterial employees. Certain species are more suitable, as they produce proteins that enable easier electron transfer. Geobacter and Shewanella species of bacteria are commonly used in MFCs.
A strain of Shewanella – S. oneidensis MR-1 —is one of the most studied and widely analyzed EAMs. They can live in the presence or absence of oxygen, they are easy to grow, and they have a well-documented genome sequence.However, primarily, their ability to easily transfer electrons is why they are so desirable in MFCs.
Natural microbial communities in waste matter like wastewater or those found at the bottom of swampy water are also good at generating bioelectricity. We can simply tap into that natural function for our bioelectric needs.
Microalgae are other efficient microorganisms used for generating bioelectricity from wastewater.
What substrates can be utilized by the bacteria?
MFCs kill two birds with one stone—they generate electricity while they break down our waste. We produce a humongous amount of all kinds of waste, which sadly ends up being dumped into landfills or into the sea, or it is burnt, releasing massive plumes of harmful gases in the air. Around 7-15% of the world’s energy requirement can be met using biomass, and now we can put all that potential waste to good use.
Sewage, food waste, mud, animal waste, or any sort of organic waste are all excellent sources of nutrients and energy that microorganisms utilize to generate bioelectricity. This still leaves us with plastic waste, but there may even be bacteria that can solve that problem.
Is bioelectricity the future?
Production of bioelectricity by MFCs is a pollution-free process. Organic matter is broken down anaerobically by bacteria to generate bioelectricity. There is no burning, no toxic gas production, or hazardous waste generation. It is a green and sustainable method of energy production.
The biggest limitation however, is the low quanta of power generated. Currently, the average MFC supplies a voltage of just 0.5 V. To put that into perspective, one Duracell AA battery supplies a voltage of 1.5 V.
Despite the small quanta of energy produced, MFCs still have their uses. One study used MFCs to power small wireless sensors that monitor ecological sites. As MFCs don’t need to be recharged, there was no fear of the sensors failing due to depleted batteries.
Another drawback is that we can’t use them at low temperatures. In cold climates, the activity of bacteria falls, and their metabolic rate decreases. Until we figure out how to keep bacteria toasty, allowing them to maintain their energy efficiency, sorry Canada, you’re not getting in on this action.
Immense dedication by scientists is going into improving the efficiency of MFCs and implementing them on a large scale. An inspired researcher in the Indian state of Gujarat, Dr. Nasreen Munshi, set up her own mini bioelectricity plant, consisting solely of MFCs. She and her fellow researchers were able to continuously harness small amounts of electricity for a few weeks.
The main focus of researchers today is to set up bioelectricitys plant at wastewater treatment sites. Even if usable amounts of energy cannot be continuously generated, whatever bioelectricity is created can be stored in capacitors. Once the quantity of bioelectricty reaches a sufficient level, it can be discharged from the capacitor.
MFC’s use of bioelectricity is innovation at its best. As long as organic matter is present, and bacteria live on earth, MFCs could be a sustainable long-term source of energy. On paper, such MFCs are an ingenious solution that tackles both our energy and waste problem. Bacteria will jump for joy (if they could feel joy or jump) when feeding off our immense quantities of organic waste, and we will be incredibly happy taking their resultant energy in return.
Imagine in a couple of decades, people’s houses or buildings will have MFCs attached to them. Instead of dumping our waste into a dustbin, we might dump it into these tiny cells that will convert it to the electricity that powers our lights. In other words, no more taking out the garbage!