How Bacteria Can Reclaim Lost Energy, Nutrients, And Clean Water From Wastewater

Wastewater contains untapped resources that, if reclaimed, could power agriculture, global sanitation, and its own treatment to help us meet UN SDG goals, according to a review published today in Frontiers in Science.

Every year, we produce about 359 billion cubic meters of wastewater globally—enough to fill Lake Geneva four times over.

Half of global wastewater is discarded, with the rest expensively and inefficiently treated for re-use. Emerging microbially-powered tech could reclaim these resources from the drain, save money, and reduce environmental harms.

Wastewater is water that’s been used and carries organic matter and nutrients—from everyday sewage (toilets, showers, laundry), industrial/commercial water (rinsing, cooling, cleaning), and food-related streams (kitchens, restaurants, food processing).

“Globally, our wastewater contains over 800,000 GWh of chemical energy—equivalent to the annual output of 100 nuclear power plants. It’s also rich in nutrients used in agricultural fertilizers which, if reclaimed, could supply 11% of global demand for ammonia and about 7% for phosphate,” said lead author Prof Uwe Schröder at the University of Greifswald, Germany.

This new review by an international team of researchers explores how technologies using electricity-generating bacteria—like those already piloted at the UK’s Glastonbury Festival and in field trials in Uganda, Kenya, and South Africa—could help us reclaim resources currently being flushed away.

However, the researchers argue that deploying this on a larger scale will need a broad coalition of researchers, water providers, and policymakers, to overcome its challenges—which range from the over-regulation of circular economics to engineering obstacles.

A circular economy of energy and nutrients
The researchers discuss microbial electrochemical technologies (METs) as a more efficient way to treat wastewater, using microbes known as electrogenic bacteria.

While microbes are already used to treat wastewater through anaerobic digestion, this approach converts just 28% of chemical energy to electricity. METs could be integrated into, and improve, such systems.

These bacteria transfer electrons to their surroundings, creating an electrical current when they are connected to electrodes in a fuel cell. In laboratory settings, they can convert up to 35% of wastewater’s chemical energy into electricity. The authors say that, in principle, the power generated could even help run the water sector itself, which currently accounts for around 4% of global energy use.

The microbes can also help to extract nutrients from wastewater, cleaning it for further use. These critical fertilizer ingredients are typically produced in energy-intensive or unsustainable processes. Removing these compounds from wastewater would have the double benefit of reclaiming valuable resources and reducing pollution—as releasing nutrient-rich wastewater can cause algal blooms in waterways, which starves fish of oxygen.

“These are valuable chemicals that we cannot afford to throw away. After removal, the resulting water can be reused in many ways, like watering crops or industrial cooling. It could then be further treated to produce drinking water,” said co-author Dr Elizabeth Heidrich from Newcastle University, UK.

There may be many other niche applications, from recycling nutrients in hydroponic systems to powering self-sustaining sensors that detect pollution.

Sanitation for all
The researchers argue that, by enhancing both sanitation and resource recovery, METs present a compelling solution to address the UN’s sixth Sustainable Development Goal to ensure availability and sustainable management of water and sanitation for all.

METs have proved efficient in pilot trials, offering the opportunity to treat more water under a wider range of conditions. For example, a urine-powered MET called Pee Power® was trialed at the Glastonbury Festival in 2015, one of the world’s largest outdoor music festivals. It has since proved successful in longer-term field trials in Uganda, Kenya, and South Africa. The system converts wastewater to electricity, powering lighting around the toilets to reduce safety risks in areas without an electricity supply.

“The journey of METs over the last twenty years has moved us from understanding the 'microbial black box' to building modular, scalable systems capable of real-world impact. We are now at a stage where these technologies are technically feasible; the next step is ensuring they are economically competitive with traditional treatment methods. By strategically integrating METs into our existing infrastructure, we can transform global wastewater management into a self-sustaining engine for resource recovery,” said Dr Deepak Pant from the Flemish Institute for Technological Research (VITO), Belgium.

“Globally, about 3.5 billion people cannot access managed sanitation. Expanding wastewater treatment could help improve living conditions for many of the world’s poorest people, as well as preventing ecological damage. Microbial electrochemical technologies could be a local solution to turn harmful sewage into a valuable resource,” said co-author Prof Ioannis Ieropoulos from University of Southampton, who also serves as a director of MET-C which is commercializing the microbial fuel cell technology.

Overcoming obstacles
Despite their potential, these technologies face challenges to widespread adoption. Tight regulatory frameworks are often not suited for circular economies that repurpose waste. For example, in many countries, urine-derived fertilizer cannot be used for growing food or animal feed.

There are also engineering obstacles in ensuring that the MET materials maintain high performance when running continuously.

“While it would be a stretch to imagine powering our homes with wastewater, microbial electrochemical technologies could enhance existing water treatment processes. Rolling METs out widely would be especially beneficial for heavy loaded types of wastewater or in places where existing treatment is too expensive or doesn’t reach everyone,” said co-author Prof Falk Harnisch, from the Helmholtz Centre for Environmental Research, Germany.