Turning Carbon Dioxide Into Renewable Diesel Fuel With Electricity & Microbes – CleanTechnica

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Instead of spewing carbon into the atmosphere where it contributes to overheating the planet we all live on, many scientists and startups want to turn it into valuable chemicals and fuel, not bury it deep underground or hide it in the pantry with our cupcakes. Researchers at Washington University in St. Louis report a new method that combines electricity and bacteria to turn carbon dioxide into fatty acids, which can ultimately be converted into renewable diesel fuel for vehicles.

The process was reported in the journal Joule on October 31, 2024. The scientists claim their new process is 45 times more efficient and requires less than 3% as much land as is needed to produce biodiesel from soybeans. “We have proven that electro-biodiesel route is much more efficient than conventional biodiesel, in particular, if you count the energy from sunlight,” says Joshua Yuan, professor of energy, environmental & chemical engineering at Washington University in St. Louis. Other members of the team included Kainan Chen, Peng Zhang, Yayun Chen, Chengcheng Fei, Jiali Yu1,  Jiahong Zhou, Yuanhao Liang, Weiwei Li, Sisi Xiang, and Susie Dai.

In the summary to their work, the researchers write,

“Efficient and sustainable energy production is essential for climate change mitigation, yet current approaches like biofuels or electro-fuels have limitations in efficiency and product profile. We advanced a new electro-biodiesel route via integrating electro-catalysis and bio-conversion to produce lipids from carbon dioxide for biodiesel. We first revealed bioenergetic and metabolic limits in C2+ intermediate utilization through simulations and metabolomics, guiding the synthetic biology design to achieve reductant balance, more ATP production, efficient lipid conversion, and higher lipid yield.

“Furthermore, we discovered specific ratios of ethanol and acetate to achieve co-substrate synergy, empowering bimetallic catalyst design to improve bioconversion efficiency. The microbial and catalyst co-design achieved a solar energy to molecule conversion efficiency of 4.5 percent for carbon dioxide to lipid conversion. Electro-biodiesel leverages the high efficiency of electrocatalysis and longer-carbon-chain products from microbial lipid synthesis, overcoming the limitations for both electrocatalysis and bioconversion.

“Electro-biodiesel achieved 45 times less land usage than soybean biodiesel, competitive economics, and substantial carbon emission reduction.Petrochemical diesel fuel accounted for a quarter of the total carbon dioxide emissions from transportation in the U.S. in 2022, according to the US Energy Information Administration. One solution to reducing the carbon emissions from diesel powered vehicles is to swap conventional diesel with biodiesel, which in the US is mainly made from soybean oil.”

The Power & Peril Of Diesel Engines

We all know diesel engines power most of the heavy duty trucks that haul our freight, deliver our children to school, pick up our trash, fight our fires, and bring cement to construction sites. Without them, our economy would grind to a halt. But we also know that in addition to carbon dioxide, they spew a toxic stew of nitrogen oxides and fine particulates that cause serious health issues in humans. Fine particulates are so small they pass directly into our bloodstream in the lungs. Then they get transported throughout the body and accumulate in our hearts, brains, livers, kidneys, and our other organs. Substituting biodiesel for conventional diesel fuel can reduce or eliminate many of those harmful effects.

And here’s the thing — heavy trucks and airplanes are deucedly difficult to decarbonize. Both require enormous amounts of power for long periods of time — something the batteries of today are simply not capable of supplying. Perhaps someday in the future they will be up to the task, but in the meantime the world needs to find solutions to diesel pollution until such time as battery technology is ready to supplant the tried and true diesel engine. As much as biofuels are not the complete answer to lowering carbon emissions from the transportation sector, they are an important step in the right direction. The ability to do make them without taking a massive amount of crop land away from food production is really good news.

In a  blog post, Anthropocene Magazine says that the traditional way of making biofuels relies on photosynthesis to grow the crops which convert sunlight and carbon dioxide into plant biomass. That process has an efficiency of less than 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 electro-catalysis, 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 electro-catalysis and bio-conversion can achieve highly efficient conversion of renewable energy, including solar energy, to bio-products, in a way much faster than natural photosynthesis,” Yuan said. “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 carbon dioxide into the chemicals, fuels, and materials we need. This will allow us to bypass the current petrochemical industry and achieve carbon circular economy.”

Biofuels Are Still Fuels

Sharp-eyed readers will note that biofuels are still fuels. They create carbon dioxide when burned in an internal combustion engine. And yet, one of the principal benefits of the new process discovered by these researchers is that it creates far fewer carbon emissions in the production phase than ordinary biodiesel. So while some carbon dioxide is created when it is burned, the total life cycle carbon dioxide created is significantly lower than it is for biodiesel made the conventional way. 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 regular biodiesel production results in 2.5 to 10 grams of carbon dioxide per gram, the researchers say.

The other major benefit of this new process is that it not only can recirculate some of the carbon dioxide created back into more biodiesel, it can do it in a way that uses a fraction of the arable land needed to make biofuels from crops like soybeans or corn. That means more land available for growing crops to feed people instead of for fuels, which is a very good thing.