Imagine being able to use electricity to power your car — even if it's not an electric vehicle
Researchers at the UCLA have for the first time demonstrated a method for converting carbon dioxide into liquid fuel isobutanol using electricity. James Liao and his team report a method for storing electrical energy as chemical energy in higher alcohols, which can be used as liquid transportation fuels.
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| Electrochemical bioreactor which was developed by UCLA's researchers |
"The current way to store electricity is with lithium ion batteries, in which the density is low, but when you store it in liquid fuel, the density could actually be very high," Liao said.
Liao and his team genetically engineered a lithoautotrophic microorganism known as Ralstonia eutropha H16 to produce isobutanol and 3-methyl-1-butanol in an electro-bioreactor using carbon dioxide as the sole carbon source and electricity as the sole energy input.
Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. There are two parts to photosynthesis — a light reaction and a dark reaction. The light reaction converts light energy to chemical energy and must take place in the light. The dark reaction, which converts CO2 to sugar, doesn't directly need light to occur.
Scientists have been able to separate the light reaction from the dark reaction and instead of using biological photosynthesis, they are using solar panels to convert the sunlight to electrical energy, then to a chemical intermediate, and using that to power carbon dioxide fixation to produce the fuel.
Liao explained that this method could be more efficient than the biological system, because the plants used require large areas of agricultural land. However, because Liao's method does not require the light and dark reactions to take place together, solar panels, for example, can be built in the desert or on rooftops.
Theoretically, the hydrogen generated by solar electricity can drive CO2 conversion in lithoautotrophic microorganisms engineered to synthesize high-energy density liquid fuels. But the low solubility, low mass-transfer rate and the safety issues surrounding hydrogen limit the efficiency and scalability of such processes. Instead Liao's team found formic acid to be a favorable substitute and efficient energy carrier.
The electrochemical formate production and the biological CO2 fixation and higher alcohol synthesis now open up the possibility of electricity-driven bioconversion of CO2 to a variety of chemicals. In addition, the transformation of formate into liquid fuel will also play an important role in the biomass refinery process, according to Liao.
