Microbes Make Methane from Waste Wind Power 0

Brita Belli | Mon Aug 20 2012

We’ve long depended on coal-fired and natural gas power plants to convert chemical fuel into electricity. Now, scientists have found a way to convert electricity into a fuel using excess power from renewables like wind and solar.

Scientists from Stanford and Pennsylvania State universities have discovered a process to convert electricity into methane—the main constituent of natural gas— using microbes. The fuel is carbon neutral and can use the excess electricity from renewable sources.

“In a sense, it’s the Holy Grail,” says Alfred Spormann, a professor of chemical, civil and environmental engineering at Stanford who is leading this research. “There is a microbiological way to convert electrical energy into chemical fuel. And methane is the most simple fuel that exists and where we have a fairly good infrastructure.”

In a sense, it’s the Holy Grail

While methane holds potential as a fuel source, it is also a potent greenhouse gas. It is released en masse from landfills, factory farms and natural gas spills and has more than 20 times the heat-trapping potential of carbon dioxide. But this microbial methane is different, Spormann says.

“The carbon for the methane comes from atmospheric CO2. So the methane that is produced by the microbial electrosynthesis is essentially carbon neutral and so will all other commodity chemicals that can be produced that way,” he says.

The electricity comes from clean energy like wind and solar and the process utilizes electricity that would otherwise be lost. With outdated transmission systems, wind farms and solar photovoltaic power plants often produce more electricity than can be used or stored. In the Pacific Northwest, wind farms were taken offline this past spring because of an increase in hydroelectric power from dams due to springtime snow melt and an outdated grid that couldn’t distribute the additional power.

This microbial technology could turn that excess electricity into useable fuel.

Here’s how the process works: As electricity flows through the cathode, the microbes pick up the electrons and metabolize them, releasing methane as a byproduct. Bruce Logan, a professor of civil and environmental engineering at Penn State, was the first to demonstrate the process in a lab, using a methanogen called Methanobacterium palustre. The microbes were spread on a cathode that was then submerged in nutrient-rich water. When an electrical current was applied, the microbes began producing methane at an 80 percent efficiency rate.

We could have prototypes in three years

But while researchers have successfully converted electricity to methane in the lab, Spormann says there are still gaps in their understanding before they can take this technology to a larger scale. “We have no idea how the enzymes are controlled,” he says. “You need to see what makes this process stable. We don’t understand the ecology of the microorganisms in these electrons to make this process stable and scalable.”

The researchers are working to identify the best candidates for conversion, by studying community mixtures of microbes, bacteria and archaea (other single-celled microorganisms). And Logan is working on advancing cathode technology to increase methane production and making electrodes from more cost-effective materials then the precious metals currently used.

Eventually, they foresee large-scale application of the technology, with microbe cultures across the country churning out methane that can be stored, channeled to various locations using existing natural gas pipelines, and used to fuel everything from airplanes to cars.

Spormann says he anticipates a working prototype within a few years. “Some prototypes we probably could have in three years,” he says. “Then the next question is to scale this up and we have to see what challenges come, but that’s been a great interface between electric chemistry and microbiology and chemical engineering.”

Top image: Moon Rise behind the San Gorgonio Wind Farm. Courtesy Flickr user Caveman Chuck Coker