Microbes could be the future of renewable energy, thanks to biobased fuel cells now being tested by the US military.
Electricity-generating microbes can sustainably power sensors and drones operating long periods underwater and underground.
More than any single application, however, microbial fuel cells can also change the way we think about climate technologies.
As climate volatility becomes the norm, these devices offer lessons on designing resilience into the very fabric of our technologies.
What are microbial fuel cells?
Biofuels are already an important pathway to decarbonise the global economy. Now, a new form of bioenergy is on the rise: microbe-generated electricity.
The tech takes advantage of a simple biological fact: microbial metabolisms generate more energy than the organism needs. Once we harvest this excess, we can turn it into usable electricity.
Microbial fuel cells have a similar structure to chemical batteries, with an anode formed from living microbes. Microbes in the anode gobble up microscopic morsels floating around in their environment. When they metabolise these, it generates excess electrons (in other words, excess energy) that move towards the cell cathode.
All this sounds like the workings of a typical battery, but there is a key difference. Batteries store energy while cells, like these microbial ones, actually generate it.
“The basic idea is that microbes move electrons around during their metabolic processes,” said Marcarelli. “In a microbial fuel cell, those processes transfer electrons from an anode to a cathode, creating an electrical current we can harness.”
These fuel cells offer key advantages over lithium batteries or petroleum energy. Most importantly, they generate energy directly from materials in their surroundings. This cuts the need for human interventions like recharging and refuelling – a critical feature where you want a device operating in remote locations for long periods of time.
Underwater reconnaissance
Microbial fuel cells are not speculative devices: they are already being successfully tested, including by the US military.
The US Defense Advanced Research Projects Agency (DARPA) and Michigan Tech researchers have successfully demonstrated microbial fuel cells prototypes off the coast of Texas. They managed to generate electricity at a depth of 9 metres below the waterline.
Why is the US government interested in this seemingly obscure energy technology? The answer lies with underwater unmanned vehicles, or UUVs.
UUVs are effectively underwater drones. Nimble and free of human crew, they offer unparalleled freedom of movement in the sea and through waterways. Unsurprisingly, UUVs hold uses in military reconnaissance, which explains DARPA’s involvement in the project.
Historically, the barrier to deploying UUVs for extended periods of time has been finding ways to power them without the vehicles needing to resurface and resupply – something that racks up operational costs.
By cutting the need to resurface for re-supply, UUVs could run autonomously across longer distances.
Filter feeding
The scientists working with DARPA encountered a technical barrier that comes with deploying microbes underwater.
The microbes only generate electricity consistently when they have enough to eat. Seawater contains a lot of microbe food, but often in diluted concentrations – too dilute for microbes to acquire consistently.
To solve this, the cell system that Michigan Tech built uses granulated activated carbon in their device. This filters incoming seawater, concentrating the microscopic biomass within and keeping the microbes in the anode well-fed.
At 225 kg, the microbial fuel cells tested on the project are hefty devices. Yet as we know from the history of chemical batteries, miniaturisation is the long-term trend we see in energy storage devices. It’s likely only a matter of time before technological advances shrink microbial fuel cells to a more manageable size.
Dirt is power
Military reconnaissance is just one area where microbial fuel cells could cut costs and optimise.
These devices also help environmental conservation. As they allow us to monitor otherwise inaccessible locations for extended periods, conservation specialists could use them to power in-situ sensors that collect long-term data.
Environmental sensing was the target application for Northwestern University’s microbial cell trials. Unlike the DARPA-led experiments, this research looked at how cells can draw on microscopic biomass found in soil.
Like seawater, soil tends to be rich in the tiny biomass particles that microbes feed on. This is what enables microbial fuel cells to operate underground.
Yet soil presents its own challenges. The researchers found that a key barrier to power generation underground is a relative lack of moisture and oxygen, which can kill the microbes. Without ready access to all the necessaries of life, there is a limit to how long the fuel cells can operate.
To overcome this, they experimented with different battery designs aimed at conserving moisture within the batteries. The top of the device is also continually exposed to the air above, ensuring a steady oxygen supply that keeps the microbes happy.
This ‘snorkel’ design meant that the fuel cells could operate not just underground but in water too. Their final prototype performed across a wide range of soil conditions, from moderately dry soil to fully submerged environments.
Precision agriculture
Microbial fuel cells have important applications for agriculture and food security, particularly in resource-constrained regions where every input counts.
These biobased cells can power soil sensors farmers can use to track field conditions in real time. This makes it a boon for precision agriculture – a type of farming that relies on data to cut waste and boost productivity.
Under precision agriculture, farmers collect data on field conditions. This information can inform decisions on how much water, fertiliser, and other inputs to put down, and when.
To practice precision agriculture effectively, farmers need up-to-the-minute data. The best way to get this is by placing remote sensors in their fields. These sensors can track soil moisture, nutrients, temperatures, and other variables that separate a bumper harvest from a meagre on.
Traditionally, finding sustainable ways to power soil and water sensors for long enough have been difficult. Cost-effective microbial fuel cells could solve this problem.
Autonomous sewage-cleaning
Microbial fuel cells work best when their organism can access plenty of food. Seawater and soil are perfect for this, both full of biomass particles.
Wastewater is a veritable buffet for microorganisms. The biological particles that make sewage so toxic for us make it an abundant source of energy for microbes. Lucky for us, this also means that microbial fuel cells are ideal for purifying sewage.
Stanford engineers have developed a low-cost, patented microbial fuel cell that eats wastewater while cleaning it at the same time.
The beauty of using microbial fuel cells to clear up wastewater like this is that the system powers itself. As microbes gobble up particle contaminants, they leave behind clean water that can be re-used. At the same time, the microbes are also generating the energy it needs to sustain themselves.
A microbial fuel cell that cleans wastewater is a perfect example of a biobased circular technology that can offer large-scale benefits at little cost. Deployed at municipal sewage works, it can enable us to recycle water sustainably. It can also be used to clear sewage spills in natural environments.
These advantages could be of use in developing countries in particular, where wastewater treatment systems are limited. The system could cut the electricity needs of treating wastewater – currently estimated at 3% of the total electrical load in developed nations.
A new kind of climate tech
So far, biobased energy has been confined to biogas and biofuels. With microbial electricity generation, synbio is intervening on the energy transition in a brand new way.
However, microbial fuel cells are more than just an energy transition technology. They should also affect a paradigm shift in how we think about, and design, climate adaption tech.
The 21st century will be the century of climate change, where hostile conditions are set to usher in a whole new economic context.
An increasingly volatile climate will limit our ability to access the technologies and resources our economies have traditionally relied on.
As competition for energy, water, fertiliser, and minerals intensifies, our reliance on complex petrochemical supply chains will become an increasing liability.
While we badly need renewables to phase out fossil energy, the mineral supply chains behind batteries and solar panels come with problems of their own – including huge amounts of ec-toxic waste.
Retaining old technological orthodoxies won’t work. To remain resilient, humanity will need to do more with less.
Where possible, this will mean developing and scaling low-input technologies that are light on their feet, needing not much more than the local resources to build and operate. These technologies should also be biodegradable without leaving toxic traces.
WIth its low-input, high-impact profile, microbial fuel cells are an important example of how biobased technologies can make limited resources go further.
Harnessing the living metabolism of simple biological organisms, researchers have built an energy generation system that requires few material throughputs.
Drawing mainly from its direct environment, these cells perform socially vital labour in diverse sectors – from maximising yields to recycling water. This will be the kind of tech that builds a new, more climate-resilient economy in the decades ahead.
The post The hum of microbial bioelectricity appeared first on World Bio Market Insights.
