One of the biggest problems with wind energy is that it is unreliable. Wind blows when it wants to and not when we need the electricity that can be made from it. This means you need overcapacity in other energy productions plants to make up for the short-fall and that is expensive. could a team of microbiologists from Stanford and Pennsylvania State universities have a solution?
The team is raising microbes that have the amazing ability to convert electricity to methane gas. If the lab experiments can be replicated on an industrial scale then the problem of storing the power generated by wind turbines for later use could be solved.
It is almost impossible to store electricity at the scale needed to be able to supply the national network so electricity generated by wind turbines at times of low demand is not of much use. If it’s possible to convert it to methane gas then it can easily be stored and used later. [pullquote]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 steps.[/pullquote]
The scientists’ goal is to create large microbial factories made up of these methanogens that will transform clean electricity from solar, wind or nuclear power into renewable and pure methane gas and other valuable chemical compounds for industry.
“Most 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.
“The whole microbial process is carbon neutral,” he explained. “All of the CO2 released during combustion is derived from the atmosphere, and all of the electrical energy comes from renewables or nuclear power, which are also CO2-free.“
“Right 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.“
Under natural circumstances the methangens live in an oxygen free environment that uses carbon dioxide for its energy source. To produce the energy they will use an electron from hydrogen in the environment.
In the bio-reactors envisaged by the research team the microbes will be fed electrons produced by renewable energy sources such as wind or solar to replace the electrons from hydrogen. that was the electricity can by converted into pure methane gas.
It’s not just a great way to store the energy for later use. The team believes that if they are successful we could be fueling our aircraft and ships with clean renewable energy. Producing a battery-powered passenger plane is not really viable but flying on liquid methane would be technically straightforward to do.
When 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.
“Microbial 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 steps.”
For this new technology to become commercially viable, a number of fundamental challenges must be addressed.
“While 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.“
In 2009, Logan’s lab 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.
The 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.
“The microbes were about 80 percent efficient in converting electricity to methane,” Logan said.
The 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.
“Microbial 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.“