Scientists Develop Biodiesel Using Electrocatalysis and Bioconversion
Diesel-powered vehicles significantly contribute to carbon emissions, making it difficult to achieve decarbonization. According to the U.S. Energy Information Administration, in 2022, diesel fuel accounted for nearly 25% of all carbon dioxide emissions from U.S. transportation and roughly 10% of emissions tied to energy use.
Researchers Joshua Yuan, who holds the Lucy & Stanley Lopata Professorship and leads the Department of Energy, Environmental & Chemical Engineering at the McKelvey School of Engineering, and Susie Dai, a MizzouForward Professor of Chemical and Biomedical Engineering at the University of Missouri, along with their colleagues at Texas A&M University, have successfully utilized electrocatalysis to turn carbon dioxide into an electro-biodiesel that is 45 times more effective and requires 45 times less land compared to traditional soybean-based biodiesel production. Their findings were published in the journal Joule on October 31.
“This innovative concept can contribute to a circular economy by producing emission-negative fuels, chemicals, materials, and food components much more efficiently than photosynthesis, while emitting less carbon than petrochemicals,” stated Yuan, who initiated this project with Dai at Texas A&M University. “We have systematically tackled issues in electro-biomanufacturing by pinpointing the metabolic and biochemical limits of using diatomic carbon and have successfully surpassed these limitations.”
The research team employed electrocatalysis—a chemical reaction triggered by electron exchanges on catalysts’ surfaces—to convert carbon dioxide into biocompatible substances, like acetate and ethanol. These intermediates were subsequently converted into lipids, or fatty acids, by microbes, leading to the creation of biodiesel feedstock, according to Yuan, the director of the National Science Foundation-funded Carbon Utilization Redesign for Biomanufacturing-Empowered Decarbonization (CURB) Engineering Research Center (ERC).
The innovative process combining microbes and catalysts allowed their electro-biodiesel to achieve a solar-to-molecule efficiency of 4.5% in converting carbon dioxide to lipids, which is significantly superior to traditional biodiesel production. Typically, natural photosynthesis in terrestrial plants yields less than 1% efficiency, where less than 1% of solar energy is transformed into biomass via the conversion of CO2 into various molecules for plant growth, explained Yuan.
“The energy dedicated to creating the biodiesel precursor, lipid, is generally even less because lipids are highly energy-dense,” he noted. “In contrast, our electro-biodiesel method can convert 4.5% of solar energy into lipids when powered by solar electricity to facilitate electrocatalysis, which is considerably more efficient than natural photosynthesis.”
To enhance electrocatalysis, the team crafted a novel catalyst composed of zinc and copper that generates diatomic carbon intermediates, which can be transformed into lipids using a specially engineered strain of the bacterium Rhodococcus jostiii (RHA1), renowned for its capability to produce high lipid content. This bacterium also improved the metabolic processing of ethanol, facilitating the conversion of acetate—an intermediate—into fatty acids.
Upon establishing this new technique, the researchers assessed its potential climate impact, discovering promising outcomes. By utilizing renewable resources in the electrocatalysis process, they identified that electro-biodiesel production could result in a reduction of 1.57 grams of carbon dioxide for each gram of electro-biodiesel produced, alongside biomass by-products and ethylene, indicating a potential for negative emissions. In comparison, traditional diesel from petroleum results in 0.52 grams of carbon dioxide per gram, while biodiesel production typically generates between 2.5 grams and 9.9 grams of carbon dioxide for each gram of lipids produced.
“This research demonstrates a viable approach for efficiently converting renewable energy into chemicals, fuels, and materials, addressing the critical constraints faced by modern society,” Yuan remarked. “This technique could alleviate the shortage of biodiesel feedstock and revolutionize the production of renewable fuels, chemicals, and materials, allowing for reduced reliance on fossil fuels, especially in sectors heavily dependent on fossil energy, such as long-haul heavy-duty transportation and aviation.”
