As far as greenhouse gases go, methane is the quiet villain that could stealthily drag us ever deeper into the climate crisis. In our atmosphere, it is at least 25 times more effective at trapping heat than carbon dioxide.
It’s also not that efficient – through burning, less than half of the energy in the natural gas can be converted into electrical power.
In an effort to squeeze more electrons from every puff of methane, researchers in the Netherlands have explored a rather unconventional form of power station – one you’d need a microscope to see.
“This could be very useful for the energy sector”, says Radboud University microbiologist Cornelia Welte.
“In the current biogas installations, methane is produced by microorganisms and subsequently burnt, which drives a turbine, thus generating power. Less than half of the biogas is converted into power, and this is the maximum achievable capacity. We want to evaluate whether we can do better using microorganisms.”
The focus of their investigation is a type of archaea – bacteria-like microbes known for their extraordinary talents of surviving under strange and harsh conditions, including being able to break down methane in environments deprived of oxygen.
This specific type, known as anaerobic methanotrophic (ANME) archaea, manage this metabolic trick by offloading electrons in a chain of electrochemical reactions, employing some kind of metal or metalloid outside of their cells or even donating them to other species in their environment.
First described in 2006, the ANME genus Methanoperedens was found to oxidize methane with a little help from nitrates, making them right at home in the wet bogs of the Netherland’s fertilizer-soaked agricultural culverts.
Attempts to pull electrons from this process in microbial fuel cells have resulted in tiny voltages being produced, without any clear confirmation on exactly which processes might be behind the conversion.
If these archaea are to ever show promise as methane-gobbling power cells, they’d really need to churn out a current in a clear, unambiguous fashion.
To make matters harder, Methanoperedens isn’t a microbe that lends itself to easy cultivation.
So Welte and her fellow researchers gathered a sample of microbes they knew to be dominated by this methane-slurping archaea, and grew them in an oxygen-lacking environment where methane was the only electron donor.
Near this colony they also placed a metal anode set at zero voltage, effectively creating an electrochemical cell primed to generate a current.
“We create a kind of battery with two terminals, where one of these is a biological terminal and the other one is a chemical terminal,” says microbiologist Heleen Ouboter, also from Radboud University.
“We grow the bacteria on one of the electrodes, to which the bacteria donate electrons resulting from the conversion of methane.”
After analyzing the conversion of methane to carbon dioxide and measuring fluctuating currents that spiked as high as 274 milliamps per square centimeter, the team deduced a little over a third of the current could be attributed directly to the breaking down of methane.
As far as efficiency goes, 31 percent of the energy in the methane had transformed into electrical power, making it somewhat comparable with some power stations.
Tinkering more with the process could see to the creation of highly efficient living batteries that run on biogas, wringing more spark from every bit of gas and reducing the need for piping methane over long distances. And that’s important because some methane power plants barely manage efficiencies of around 30 percent.
But optimistically, we ought to find ways to wean ourselves from our addiction to all fossil fuels.
Technological applications aside, though, learning more about the various ways this insidious greenhouse gas breaks down in our environment can’t be a bad thing.
This research was published in Frontiers in Microbiology.