Instead of spewing planet-warming carbon dioxide emissions into the atmosphere, many scientists and startups want to turn the greenhouse gas into valuable chemicals and fuels.

Researchers now report a new method that combines electricity and bacteria to turn carbon dioxide into fatty acids, which can ultimately be converted into biodiesel for vehicles. The process, reported in the journal Joule, is 45 times more efficient and takes about 45^th of the land needed to produce biodiesel from soybeans.

Petrochemical diesel fuel accounted for a quarter of the total carbon dioxide emissions from transportation in the U.S. in 2022, according to the U.S. Energy Information Administration. One solution to reducing the carbon emissions from diesel-powered vehicles is to swap conventional diesel with biodiesel, which in the U.S. is mainly made from soybean oil.

Making biofuels of course relies on photosynthesis which converts sunlight and carbon dioxide into plant biomass with an efficiency under 1%. The new method, meanwhile, converts 4.5% of solar energy to the fatty acids when the process is driven by electricity from a solar panel.

The research team used a process called electrocatalysis, which relies on a catalyst to speed up chemical reactions. They designed a new zinc- and copper-based catalyst that converts carbon dioxide into intermediate compounds. Then they use an engineered bacterium to convert those compounds into fatty acids for biodiesel production.

“Combining electrocatalysis and bioconversion can achieve highly efficient conversion of renewable energy, including solar energy, to bioproducts, in a way much faster than natural photosynthesis,” Yuan says. “Practically speaking, we can envision a future of electrifying chemical and fuel industries, where low cost renewable or fusion electrons will drive the conversion of CO2 into the chemicals, fuels, and materials we need. This will allow us to bypass the current petrochemical industry and achieve carbon circular economy.”

For each gram of biodiesel produced, the process reduces 1.57 grams of carbon dioxide, resulting in negative emissions. By contrast, conventional petro-diesel production gives 0.52 grams of carbon dioxide per gram, and biodiesel production results in 2.5 – 10 grams of carbon dioxide per gram.

Source: Kainan Chen et al, Electro-biodiesel empowered by co-design of microorganism and electrocatalysis, Joule, 2024.

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