Microbial fuel cells: A clean energy and waste solution for Nepal’s future

In many towns and villages across Nepal, waste piles up in rivers, streets or fields. What if that same waste could be used to light a bulb or change your phone?

At first, it just looks like garbage. Vegetable peels, leftover food, and animal waste are often seen lying around near homes, farms, and marketplaces. Most people think it is useless and pay no attention to it. But what if that waste could actually help produce electricity?

Every day, Nepal creates a large amount of biodegradable waste, and most of it is left unused. This is where microbial fuel cells (MFCs) can help. They are a simple technology that uses bacteria to break down waste and turn it into electricity.

This energy can be used to light homes, power small bulbs, or even charge a mobile phone. If used properly in rural areas, MFCs could help reduce power cuts, improve daily life, and give real value to the waste we usually throw away.

What are microbial fuel cells?

Microbial Fuel Cells (MFCs) are bio electrochemical systems that use microorganisms to directly convert chemical energy in the form of organic matter into electrical energy. 

A microbial fuel cell (MFC) is a bioelectrochemical system that drives a current by using bacteria and mimics the action of a chemical fuel cell. They generate electricity with the assistance of bacteria and microorganisms of the environment. This process of electricity generation occurs under anaerobic conditions, using the metabolic processes of the microbes.

They were first conceptualised in the early 20th century, with M C Potter, who demonstrated electricity generation by E. coli in 1911 in the United Kingdom. However, significant development began in the 1980s and 2000s, as interest among the scientists grew in sustainable energy and wastewater treatment using electrogenic bacteria.

The development of microbial fuel cells has contributed to cleaner energy production and efficient wastewater treatment, reducing environmental pollution and greenhouse gas emissions. By converting organic waste into electricity, MFCs offer a sustainable solution for energy and environmental challenges. They are unique as they simultaneously clean waste and generate electricity, offering a sustainable approach to energy and environmental challenges.

Microorganismas used in MFCs are namely: Geobacter sulfurreducens (Geobacter), Shewanella oneidensis (Shewanella), Pseudomonas aeruginosa (Pseudomonas), Rhodoferax ferrireducens (Rhodoferax), Escherichia coli (E. coli), Desulfuromonas acetoxidans (Desulfuromonas), Clostridium butyricum (Clostridium), Bacillus subtilis (Bacillus), Enterobacter cloacae (Enterobacter), Acinetobacter calcoaceticus (Acinetobacter), Klebsiella pneumoniae (Klebsiella), Lactobacillus plantarum (Lactobacillus), Saccharomyces cerevisiae (Yeast), Aeromonas hydrophila (Aeromonas) and Paenibacillus polymyxa (Paenibacillus).

Construction of microbial fuel cell

Source:https://upload.wikimedia.org/wikipedia/commons/d/de/Microbial_Fuel_Cell.png

A microbial fuel cell consists of 2 half cells. They are an anode half-cell and a cathode half-cell. These two half-cells are usually separated by a special layer called a proton exchange membrane (PEM), which allows only certain particles like protons to pass through and restricts oxygen from passing through it.

In the anode half-cell, there is no oxygen, and it contains bacteria and a liquid with organic matter like sugar, wastewater, or food waste. The bacteria feed on this organic matter and release electrons and protons as they break it down. A solid material called the anode (usually made of carbon) is placed in this chamber. The bacteria attach to the anode and transfer the electrons they produce to it. These electrons then travel from the anode through an external circuit to the cathode chamber. This flow of electrons through the wire creates electricity.

The cathode half-cell usually contains oxygen, either from the air or dissolved in water. It also has a cathode electrode (made of carbon or metal). As the electrons arrive at the cathode, the protons (which passed through the PEM) and oxygen from the air combine with these electrons to form water. In some simple designs, the cathode is exposed directly to air, so there’s no need to fill the second chamber with liquid.

In short, a microbial fuel cell is built with two parts, an anode and a cathode, separated by a membrane. Bacteria at the anode break down waste and release electrons, which flow through a wire to make electricity. This simple setup helps produce clean energy while also reducing waste and organic matter in the surroundings.

Biological mechanisms of electrogens

Electrogens are a type of bacteria that can produce electricity as they break down organic materials like glucose or waste. During this process, they release electrons and protons. Unlike normal bacteria that use these electrons internally, electrogens transfer them outside their cells to a surface called an anode.

This can happen directly through tiny structures called nanowires or with the help of chemical compounds that carry the electrons. The electrons then flow through a wire to a cathode, creating an electric current. This unique ability of electrogens makes them useful in microbial fuel cells, where they help convert waste into clean energy.

Types of waste that can be used in MFCs

Microbial Fuel Cells (MFCs) can utilize a wide range of organic wastes, making them a versatile and sustainable technology for both energy generation and waste management. The bacteria within MFCs break down organic compounds found in materials such as domestic and industrial wastewater, agricultural residues, and food waste to produce electricity.

Sources like sewage sludge, animal manure, and cellulose-rich materials including paper and plant biomass are particularly valuable because they contain high levels of biodegradable matter that support bacterial growth and electron production. This flexibility allows MFCs to be integrated into various sectors, from households to industries and farms, turning different waste streams into useful energy.

In countries like Nepal, where organic waste from agriculture and food industries is abundant, MFCs could serve as an effective dual-purpose solution reducing environmental pollution while producing renewable power. By transforming everyday waste into energy, MFCs demonstrate how biological processes can help create a more circular and sustainable economy.

How to improve efficiency of MFCs?

MFCs can become more powerful, reliable, and affordable so that they can be used in homes, industries, and remote areas for clean energy and waste treatment. The following factors play an important role in order to increase the efficiency and effectiveness of MFCs:

1. Anode modification: Since electrogens get attached to the anode surface, it is important to select anode materials with excellent performance. For excellent performance of the anode, materials like carbon paper, carbon cloth, graphite rod, graphite fibre brush and reticulated vitreous carbon can be used. Also, to obtain high performance, anode noble metals like Au, Pt and Pd and transition metals like Mn, Mo and Ru can be used. Anode material helps determine anode potential, thereby maintaining stability of biofilm, shortening the start-up time for MFCs and helping in long-term operation of MFCs. Specifically, polyaniline (PANI), polypyrrole (PPy), and polyneutral red film help to improve conductivity, improve biofilm production, and increase surface area, leading to better output of MFCs. Researchers have found that stainless steel mesh modified with graphene, a member of the carbon family, provides a large specific surface area and greater attachment of microorganisms to the anode surface, which increases the power generation performance of MFCs.

2. Choosing strong electrogenic bacteria: Geothrix sulfurreducens and Shewanella oneidensis, having their own electron shuttles, are considered beneficial because they directly transfer electrons to electricity. Due to the electron transfer ability, Geothrix and Shewanella are considered potential electrogens for MFCs. They have the capacity to respire with the help of solid extracellular electron acceptors, which enables them to conduct electrons across the cell envelope, thereby increasing the efficiency of MFCs.

3. Increasing biosurfactant production through genetic modification: This approach of increasing efficiency of MFCs was developed by Zheng et al. (2015). The effectiveness of MFCs can be enhanced with the aid of biosurfactant. This biosurfactant increases the production of the rhlA gene, responsible for rhamnolipid production from Pseudomonas aeruginosa, a genetically modified electrogen. The electron transport across the membrane increases when the membrane permeability increases. A study finds that this genetically modified electric bacteria, Pseudomonas aeruginosa, increased the efficiency of MFCs up to 2.5 times more than that with the parent strain.

4. Reducing internal resistance: Reducing internal resistance in MFCs is a crucial factor for improving output voltage and power efficiency. Using highly conductive materials like carbon cloth, carbon paper or graphite felt can lower the ohmic resistance. It is also important to shorten the distance between the anode and cathode. The membrane that separates the anode and cathode should be made up of Nafion that has low ionic resistance. It has been found that using oxygen reduction catalysts like MnO₂and Pt helps to reduce the activation resistance. Likewise, coupled MFCs (MFC design where anode and cathode compartments are physically connected that allows direct interaction) are more effective in reducing internal resistance than the uncoupled MFCs. Coupled MFCs reduce internal resistance by enhancing ion transport, improving electrode contact and minimising distance between electrodes.

How are developing countries piloting MFCs?

In India, researchers at the Indian Institute of Technology (IIT) Delhi have developed microbial fuel cells that use wastewater from dairy farms to generate electricity. The organic matter in the dairy wastewater acts as fuel for the bacteria in the MFC, which breaks it down to produce power while also treating the wastewater. This project helps rural dairy farms manage their waste more sustainably and provides a small-scale electricity source for farm operations.

In China, a team at Zhejiang University created MFCs that use rice straw, an abundant agricultural waste, as the organic substrate. The rice straw is first broken down by microbes, and the electrons released during this process generate electricity. This approach offers a way to reduce pollution from burning crop residues and produce clean energy for rural communities.

In South Africa, a pilot project near Cape Town uses domestic sewage wastewater in MFC systems to both clean the water and generate electricity. The bacteria in the MFC consume the organic waste in the sewage, reducing harmful pollutants, while the electrons produced are captured as electrical energy to power small devices in the local community.

These examples highlight how specific types of waste are being used in MFCs in developing countries to solve energy and environmental problems.

Why do MFCs matter for Nepal?

Microbial Fuel Cells (MFCs) offer Nepal a sustainable and weather-resilient alternative to its hydro-dependent energy system. By converting organic waste into electricity, MFCs can help stabilize energy supply during dry seasons and reduce dependence on imported fossil fuels.

This technology also addresses waste management challenges by turning agricultural residues and household organic waste into a valuable energy source. For rural and off-grid communities, MFCs can serve as a decentralized and eco-friendly power option, aligning well with Nepal’s vision for clean and inclusive energy development.

However, realizing the full potential of MFCs will require overcoming several hurdles, including high installation costs, technical limitations, and inadequate policy support. To move forward, Nepal must prioritize research and innovation in local universities, train technical professionals, and initiate pilot projects using affordable, locally available materials. Strong government backing and public awareness will be essential to scale up this technology.

If properly implemented, MFCs could play a transformative role in achieving Nepal’s energy sustainability goals while promoting greener waste management practices.

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