that convert electricity into methane gas could become an important source of
renewable energy, according to scientists from Stanford and Pennsylvania State
at both campuses are raising colonies of microorganisms, called methanogens,
which have the remarkable ability to turn electrical energy into pure methane—the
key ingredient in natural gas. The scientists’ goal is to create large
microbial factories that will transform clean electricity from solar, wind, or
nuclear power into renewable methane fuel and other valuable chemical compounds
of today’s methane is derived from natural gas, a fossil fuel,” said Alfred
Spormann, a professor of chemical engineering and of civil and
environmental engineering at Stanford. “And many important organic
molecules used in industry are made from petroleum. Our microbial approach
would eliminate the need for using these fossil resources.”
methane itself is a formidable greenhouse gas, 20 times more potent than carbon
dioxide, the microbial methane would be safely captured and stored, thus
minimizing leakage into the atmosphere, Spormann said.
whole microbial process is carbon neutral,” he explained. “All of the
carbon dioxide released during combustion is derived from the atmosphere, and
all of the electrical energy comes from renewables or nuclear power, which are
also carbon dioxide-free.”
microbes, he added, could help solve one of the biggest challenges for
large-scale renewable energy: What to do with surplus electricity generated by
photovoltaic power stations and wind farms.
now there is no good way to store electricity,” Spormann said.
“However, we know that some methanogens can produce methane directly from
an electrical current. In other words, they metabolize electrical energy into
chemical energy in the form of methane, which can be stored. Understanding how
this metabolic process works is the focus of our research. If we can engineer
methanogens to produce methane at scale, it will be a game changer.”
Burning natural gas accelerates global warming by releasing carbon dioxide
that’s been trapped underground for millennia. The Stanford and Penn State team
is taking a “greener” approach to methane production. Instead of
drilling rigs and pumps, the scientists envision large bioreactors filled with
methanogens—single-cell organisms that resemble bacteria but belong to a
genetically distinct group of microbes called archaea.
human standards, a methanogen’s lifestyle is extreme. It cannot grow in the
presence of oxygen. Instead, it regularly dines on atmospheric carbon
dioxideand electrons borrowed from hydrogen gas. The byproduct of this
microbial meal is pure methane, which methanogens excrete into the atmosphere.
researchers plan to use this methane to fuel airplanes, ships, and vehicles. In
the ideal scenario, cultures of methanogens would be fed a constant supply of
electrons generated from emissions-free power sources, such as solar cells,
wind turbines, and nuclear reactors. The microbes would use these clean
electrons to metabolize carbon dioxide into methane, which can then be
stockpiled and distributed via existing natural gas facilities and pipelines
the microbial methane is burnt as fuel, carbon dioxide would be recycled back
into the atmosphere where it originated from—unlike conventional natural gas
combustion, which contributes to global warming.
methane is much more ecofriendly than ethanol and other biofuels,”
Spormann said. “Corn ethanol, for example, requires acres of cropland, as
well as fertilizers, pesticides, irrigation, and fermentation. Methanogens are
much more efficient, because they metabolize methane in just a few quick
For this new technology to become commercially viable, a number of fundamental
challenges must be addressed.
conceptually simple, there are significant hurdles to overcome before
electricity-to-methane technology can be deployed at a large scale,” said Bruce
Logan, a professor of civil and environmental engineering at Penn
State. “That’s because the underlying science of how these organisms
convert electrons into chemical energy is poorly understood.”
2009, Logan’s laboratory was the first to demonstrate that a
methanogen strain known as Methanobacterium palustre could convert an
electrical current directly into methane. For the experiment, Logan and his
Penn State colleagues built a reverse battery with positive and negative
electrodes placed in a beaker of nutrient-enriched water.
researchers spread a biofilm mixture of M. palustre and other microbial
species onto the cathode. When an electrical current was applied, the M.
palustre began churning out methane gas.
microbes were about 80 percent efficient in converting electricity to
methane,” Logan said.
rate of methane production remained high as long as the mixed microbial
community was intact. But when a previously isolated strain of pure M.
palustre was placed on the cathode alone, the rate plummeted, suggesting
that methanogens separated from other microbial species are less efficient than
those living in a natural community.
communities are complex,” Spormann added. “For example,
oxygen-consuming bacteria can help stabilize the community by preventing the
build-up of oxygen gas, which methanogens cannot tolerate. Other microbes
compete with methanogens for electrons. We want to identify the composition of
different communities and see how they evolve together over time.”
To accomplish that goal, Spormann has been feeding electricity to laboratory
cultures consisting of mixed strains of archaea and bacteria. This microbial
zoo includes bacterial species that compete with methanogens for carbon
dioxide, which the bacteria use to make acetate—an important
ingredient in vinegar, textiles and a variety of industrial chemicals.
might be organisms that are perfect for making acetate or methane but haven’t
been identified yet,” Spormann said. “We need to tap into the
unknown, novel organisms that are out there.”
State, Logan’s lab is designing and testing advanced cathode
technologies that will encourage the growth of methanogens and maximize
methane production. The Penn State team is also studying new materials for
electrodes, including a carbon-mesh fabric that could eliminate the need for
platinum and other precious metal catalysts.
of these materials have only been studied in bacterial systems but not in
communities with methanogens or other archaea,” Logan said. “Our
ultimate goal is to create a cost-effective system that reliably and robustly
produces methane from clean electrical energy. It’s high-risk, high-reward research,
but new approaches are needed for energy storage and for making useful organic
molecules without fossil fuels.”
Source: Stanford University