How bacteria can reclaim lost energy, nutrients, and clean water from wastewater

Frontiers

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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.  

ENDS 

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Journal

Frontiers in Science

DOI

10.3389/fsci.2026.1688727 

Method of Research

Systematic review

Subject of Research

Not applicable

Article Title

Waste to value: microbial electrochemical technologies for sustainable water, material and energy cycles

Article Publication Date

24-Feb-2026

COI Statement

The authors declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The Frontiers in Science Editorial Office assisted in the conceptualization of Figures 7, 9 in this article. The reviewer JD declared a past collaboration with the author EH to the handling editor. The authors UW, FJ, SAP, and AER declared that they were an editorial board member of Frontiers at the time of submission. This had no impact on the peer review process and the final decision.

 

Fast-paced lives demand faster vision: ecology shapes how “quickly” animals see time

Trinity College Dublin

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Dr Clinton Haarlem in Trinity College Dublin

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Credit: Trinity College Dublin

Animals don’t just see the world differently from one another, they experience time itself at dramatically different speeds. That is according to a new study that considered 237 species across the animal kingdom, and which revealed that how fast an animal lives and moves strongly predicts how quickly it can visually process the world around it.

In research published in leading international journal Nature – Ecology & Evolution, scientists from Trinity College Dublin and the University of Galway show that species with fast-paced ecologies, such as flying animals and “pursuit predators”, which chase fast, manoeuvrable prey, have much faster visual perception than slow-moving or sedentary species. 

“From a dragonfly tracking prey in mid-air to a starfish grazing slowly across the seabed, animals live in very different perceptual worlds,” said lead author Dr Clinton Haarlem, from Trinity’s School of Natural Sciences and Trinity College Institute of Neuroscience. “Our results show that these differences are not random. Instead, they are closely linked to how animals move, hunt, and interact with their environments.”

The findings provide the strongest evidence to date that ecology and evolution shape the tempo of perception across life on Earth.

Measuring the speed of sight

The researchers analysed data from 237 species from a wide range of groups, including insects, birds, mammals, and fish. To measure how quickly animals can process visual information, they used a standard metric called “critical flicker fusion (CFF)”, which is the fastest rate at which a flickering light can be perceived as distinct rather than continuous.

Higher CFF values indicate faster visual processing. While humans typically perceive flicker up to around 60 Hz, some insects and birds can detect changes at more than 200 flashes per second, effectively experiencing a slower-moving world.

The team then tested how CFF relates to ecological traits such as locomotion, foraging strategy, body size, and light environment.

Among the key results were:

• Flying species have the fastest visual perception, with CFF values roughly twice as high as non-flying animals.
• Pursuit predators have significantly higher temporal resolution than species feeding on stationary or slow-moving food
• Light environment matters: species active in bright conditions generally have faster vision than those living in darkness or deep water
• In aquatic environments, smaller, more manoeuvrable species tend to see faster than larger ones

“These results support a long-standing idea known as Autrum’s hypothesis, which in simple terms states that sensory systems evolve to match an animal’s way of life,” said co-author Dr Kevin Healy, from the University of Galway. “What’s new is that we demonstrate this pattern across the entire animal kingdom, not just within small groups of species.”

Why perception speed matters

Fast visual processing allows animals to react to rapid changes, which is crucial for flight, hunting, and avoiding predators – but that comes at a cost. Rapid neural processing requires more energy, meaning high-speed vision is only favoured when it provides a clear ecological advantage.

The findings also raise concerns about the impacts of artificial lighting and flicker in human-modified environments.

“These findings suggest species with fast visual systems may be especially vulnerable to flickering artificial lights,” said Dr Haarlem. “This could affect their hunting success, navigation, and impact predator–prey interactions, particularly in birds and aquatic predators.”

By linking ecology, evolution, and perception, the study ultimately highlights how animals inhabit fundamentally different sensory realities even when they share the same habitat.

“Understanding how animals perceive time helps us understand how they behave, evolve, and respond to environmental change,” said Dr Haarlem. “It reminds us that the world we experience is just one version of many.”

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Journal

Nature Ecology & Evolution

DOI

10.1038/s41559-026-02994-7 

Global warming and heat stress risk close in on the Tour de France

An analysis of 50 years of climate data shows that the race has so far avoided the most extreme conditions, although the risk is steadily increasing

Barcelona Institute for Global Health (ISGlobal)

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The progressive rise in temperatures poses a growing threat to the staging of summer sporting events in Europe and, more specifically, to the Tour de France, due to the increasing risk of heat stress for athletes. This is one of the conclusions of a study published in Scientific Reports, which analysed climate data associated with more than 50 editions of the French race. The research was led by the French National Research Institute for Sustainable Development (IRD) within the European project TipESM, in collaboration with institutions such as the London School of Hygiene & Tropical Medicine (LSHTM) and the Barcelona Institute for Global Health (ISGlobal), a centre supported by the ”la Caixa” Foundation.

The aim of the newly published study was to assess under which heat stress risk levels the Tour de France has taken place at different locations and dates between 1974 and 2023. The results show that, at the times and places where the race is held, heat stress risk has increased steadily over the years, with the most recent decade accumulating the highest number of extreme heat episodes. Despite this trend, the Tour has so far managed to avoid conditions of maximum health risk, in some cases by only a matter of days or tenths of a degree.

 

An ‘extremely fortunate’ race

“In our analysis, we observe that the city of Paris, for example, has crossed the high-risk threshold for heat on five occasions in July, four of them since 2014. Other cities have experienced many days of extreme heat in July, but thankfully not on the date of a Tour de France stage,” explains Ivana Cvijanovic, researcher at IRD and first author of the study.

“In a way, we can say that it is an extremely fortunate race, but with record-breaking heatwaves becoming more frequent, it is only a matter of time before the Tour encounters extreme heat stress day that will test existing safety protocols,” she adds.

 

Regions at higher risk

The researchers found that episodes of dangerous heat levels have been most common around Toulouse, Pau and Bordeaux in southwestern France, and around Nîmes and Perpignan in the southeast. They also warn that locations such as Paris and Lyon are increasingly crossing the high-risk heat threshold, becoming new heat stress hotspots. “Extra caution should be exercised when planning stages in these regions,” says Desislava Petrova, researcher at ISGlobal.

By contrast, classic mountain stage locations such as the Col du Tourmalet and Alpe d’Huez have historically remained within low to moderate heat stress risk thresholds, with no recorded episodes of extreme heat risk to date.

Regarding the time of day, the analysis shows that morning hours remain the safest part of the day, while high heat stress levels can persist until late in the afternoon.

These patterns highlight the need to adapt schedules, routes and safety protocols in order to reduce risks for both cyclists and event staff and spectators.

 

Heat, a growing risk for all sports

In this study, the researchers use the Tour de France to illustrate the broader challenge that rising temperatures driven by climate change pose to the organisation of summer sporting events, particularly in elite sport.

Heat not only affects athletic performance but can also pose a serious risk to athletes’ health. For this reason, the Union Cycliste Internationale (UCI), like FIFA and other international sports federations, has implemented safety protocols that assess heat risk and trigger protective measures, such as hydration or cooling breaks in football. However, each federation defines its own risk thresholds, and no universal standard currently exists across sports.

 

The need for physiological data to refine risk assessment

 “Science still has many unanswered questions about how the human body responds to heat, and even more so in the case of elite athletes, who face sustained physical exertion while also having physical conditioning and training levels well above those of the general population,” says James Begg, researcher at Galson Sciences. “To investigate sport-specific vulnerabilities, we would need access to anonymised physiological data that would allow us to go beyond heat indices alone.”

 

Methodology

Many heat safety protocols used by international sports federations are based on a heat index known as the Wet Bulb Globe Temperature (WBGT), which combines several meteorological variables — including air temperature, relative humidity, solar radiation and wind — to estimate heat-related health risk.

To conduct the study, the research team retrieved historical meteorological records for 12 locations frequently visited by the Tour de France, as well as for all July dates corresponding to the different editions of the race. Using these data, they calculated WBGT values and analysed the occasions on which the high-risk category in the UCI protocol (above 28 °C WBGT) was reached.

Table 1. The highest Wet Bulb Globe Temperature (WBGT) values recorded at 1500 h from 1974 to 2023: Race dates vs. All days in July

	Highest WBGT Values
Location	TdF race dates	All days in July
Paris	26.8 °C in 2002	28.8 °C in 2019
Nimes	27.9 °C in 2019	30 °C in 2020
Bordeaux	28.7 °C in 1995	30.1 °C in 2019
Toulouse	27.5 °C in 2003	29.7 °C in 2020
Col du Tourmalet	23 °C in 2006	25.9 °C in 2019
Alpe d’Huez	20.1 °C in 1992	22.7 °C in 2015
Pau	27.8 °C in 1995	28.8 °C in 2019
Nice	22.7 °C in 1975	27.6 °C in 2018
Grenoble	22.5 °C in 2014	26.4 °C in 2018

 

Reference

Cvijanovic I, Begg JD, Mistry MN, Petrova D, Brimicombe C, Sultan B. The future of European outdoor summer sports through the lens of 50 years of the Tour de France. Scientific Reports. 2026 (in press).

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Journal

Scientific Reports

DOI

10.1038/s41598-025-30129-8 

Method of Research

Observational study