Electro-biodiesel: Scientists make fuel from CO2 that’s 45x more efficient

Vehicles powered by diesel contribute significantly to carbon emissions, making the journey toward decarbonization a tough road.

According to data from the U.S. Energy Information Administration, in 2022, diesel fuel accounted for approximately 25% of the total carbon dioxide emissions from transportation in the U.S. and around 10% of the overall carbon dioxide emissions related to energy.

To address this issue, Joshua Yuan from the Department of Energy, Environmental, and Chemical Engineering at Washington University, along with Susie Dai, a MizzouForward Professor of Chemical and Biomedical Engineering at the University of Missouri, have developed a method using electrocatalysis to convert carbon dioxide into electro-biodiesel.

This new process is 45 times more efficient and requires 45 times less land than traditional soybean-based biodiesel production.

The results of their work are published online in Joule.

Electro-biodiesel

“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 Yuan, who began the work with Dai at Texas A&M University.

“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.”

The team used electrocatalysis, a 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.

Microbes then converted the intermediates into lipids, or fatty acids, and ultimately became biodiesel feedstock, said Yuan, also director of the National Science Foundation-funded Carbon Utilization Redesign for Biomanufacturing-Empowered Decarbonization (CURB) Engineering Research Center (ERC).

The novel microbial and catalyst process developed by Yuan, Dai, and their teams allowed their electro-biodiesel to reach 4.5% solar-to-molecule efficiency for converting carbon dioxide to lipid, which is considerably more efficient than biodiesel.

Yuan explained that natural photosynthesis in land plants is normally below 1%, where less than 1% of sunlight energy is converted to biomass by converting CO2 into diverse molecules for plant growth.

CO2 to fuel

“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% of solar energy to lipids when a solar panel produces electricity to drive electrocatalysis, 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 prompt the conversion of acetate, an intermediate, to fatty acid.

After developing the novel process, the team analyzed its impact on climate change and found encouraging results.

By using renewable resources for electrocatalysis, the electro-biodiesel process could reduce 1.57 grams of carbon dioxide per gram of electro-biodiesel produced with the by-products of biomass, ethylene, and others, giving it the potential for negative emissions.

In contrast, conventional diesel production from petroleum produces 0.52 grams of carbon dioxide per gram, and biodiesel production methods produce 2.5 grams to 9.9 grams of carbon dioxide per gram of lipids produced.

“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.”