Researchers develop lipid biodiesel feedstock from electrocatalysis of CO2
Researchers at the University of Missouri, Washington University in St. Louis and Texas A&M University have used electrocatalysis of carbon dioxide to create “electro-biodiesel” that they say is 45 times more efficient and uses 45 times less land than soybean-based biodiesel production.
Results of their work are published online in Joule Oct. 31, 2024.
“This novel idea can be applied to the circular economy to manufacture emission-negative fuels, chemicals, materials and food ingredients at a much higher efficiency than photosynthesis and with fewer carbon emissions than petrochemicals,” said Joshua Yuan, a professor at Washington University, who began the work at Texas A&M University with Susie Dai, a professor at the University of Missouri.
“We have systemically addressed the challenges in electro-biomanufacturing by identifying the metabolic and biochemical limits of diatomic carbon use and have overcome these limits,” Yuan said.
The team used electrocatalysis, a type of chemical reaction initiated by electron transfers to and from reactants on surfaces of catalysts, to convert carbon dioxide into biocompatible intermediates, such as acetate and ethanol.
The intermediates were then converted by microbes into lipids, or fatty acids, and ultimately became biodiesel feedstock, Yuan said.
The novel microbial and catalyst process developed by Yuan, Dai and their teams allowed their electro-biodiesel to reach 4.5 percent solar-to-molecule efficiency for converting carbon dioxide to lipid, which they say is considerably more efficient than biodiesel.
Nature photosynthesis in land plants is normally below 1 percent, where less than 1 percent of sunlight energy is converted to plant biomass by converting CO2 to diverse molecules for plant growth, Yuan explained.
“The amount of energy diverted to the biodiesel precursor, lipid, is even lower as lipid has high energy intensity,” he said. “On the contrary, the electro-biodiesel process can convert 4.5 percent of solar energy to lipids when a solar panel is used to produce electricity to drive electrocatalysis, which is much higher than the natural photosynthetic process.”
To prompt the electrocatalysis, the team designed a new zinc- and copper-based catalyst that produces diatomic carbon intermediates that could be converted into lipids with an engineered strain of the Rhodococcus jostiii (RHA1) bacterium, known to produce high lipid content.
This strain also boosted the metabolic potential of ethanol, which could help to prompt conversion of acetate, an intermediate, to the fatty acid.
After developing the novel process, the team analyzed the impact of the process on climate change and found encouraging results.
By using renewable resources for the electrocatalysis, the electro-biodiesel process could reduce 1.57 grams of carbon dioxide per gram of electro-biodiesel produced with the byproducts of biomass, ethylene and others, giving it the potential for negative emissions.
In contrast, the conventional diesel fractionation step alone from petroleum produces 0.52 grams of carbon dioxide per gram, and the total emission for diesel is over 4 grams of carbon dioxide per gram.
Despite less carbon emission, conventional biodiesel production methods also have challenges to achieve negative emission.
“This research proves the concept for a broad platform for highly efficient conversion of renewable energy into chemicals, fuels and materials to address the fundamental limits of human civilization,” Yuan said. “This process could relieve the biodiesel feedstock shortage and transform broad, renewable fuel, chemical and material manufacturing by achieving independence from fossil fuel in the sectors that are fossil-fuel dependent, such as long-range heavy-duty vehicles and aircraft.”
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