Manipulated bacteria could be a missing link in energy storage

One of the big problems of sustainable energy systems is how to store electricity generated by wind, sun and waves. At present, no existing technology allows for large-scale storage and energy recovery for sustainable energy at a low financial and environmental cost.

Electroactive microbes manufactured could be part of the solution. These microbes are able to borrow an electron from solar or wind electricity and use this energy to separate the carbon dioxide molecules from the air. The microbes can then use the carbon atoms to make biofuels, such as isobutanol or propanol, that could be burned in a generator or added to gasoline, for example.

"We believe that biology plays an important role in creating a sustainable energy infrastructure," said Buz Barstow, assistant professor of biological and environmental engineering at Cornell University. "Some roles will be supporting roles and others will be leading roles, we are trying to find all the places where biology can work."

Barstow is the lead author of "Storage of Electrical Energy with Modified Biological Systems", published in the Biological Engineering Journal.

The addition of electrical engineering elements (synthetic or non-biological) could make this approach even more productive and efficient than microbes alone. At the same time, having many options also creates too many technical choices. The study provides information to determine the best design as needed.

"We are proposing a new approach of combining biological and non-biological electrochemical engineering to create a new method of energy storage," said Farshid Salimijazi, a graduate student at Barstow Lab and lead author of the journal. .

Natural photosynthesis is already an example for storing solar energy on a large scale and turning it into biofuels in a closed carbon loop. It captures about six times more solar energy a year than any civilization uses simultaneously. But photosynthesis is really inefficient at harvesting sunlight, absorbing less than 1% of the energy that strikes the photosynthetic cells.

Electroactive microbes replaced biological light collection with photovoltaics. These microbes can absorb electricity in their metabolism and use this energy to convert CO2 into biofuels. This approach holds great promise for the production of biofuels with increased efficiency.

Electroactive microbes also allow the use of other types of renewable electricity, not just solar electricity, to fuel these conversions. In addition, some species of modified microbes can create bioplastics that can be buried, thus removing carbon dioxide (a greenhouse gas) from the air and sequestering it into the soil. Bacteria could be designed to reverse the process by converting a bioplastic or biofuel into electricity. These interactions can all occur at ambient temperature and pressure, which is important for efficiency.

The authors emphasize that non-biological methods of using electricity for carbon sequestration (assimilation of carbon from CO2 into organic compounds, such as biofuels) are beginning to approach and even exceed the capabilities of microbes. However, electrochemical technologies can not create the types of complex molecules needed for biofuels and polymers. Electroactive microbes designed could be designed to convert these simple molecules into much more complicated molecules.

Combinations of modified microbes and electrochemical systems could greatly exceed the efficiency of photosynthesis. For these reasons, a design that combines the two systems is the most promising solution for energy storage, according to the authors.

"From the calculations we have done, we think it's entirely possible," Salimijazi said.

The document includes performance data on biological and electrochemical designs for carbon fixation. The current study is "the first time anyone brings together in the same place all the data you need to compare, from one apple to another, the effectiveness of all these different ways of fixing carbon," he said. Barstow.

In the future, researchers plan to use the collected data to test all possible combinations of electrochemical and biological components and find the best combinations among so many choices.

Erika Parra, Director of MultiPHY Laboratories, Inc., is co-author of the document.