New CO2-to-fuel process could make carbon capture more economical
Researchers from the University of Toronto Faculty of Applied Science & Engineering have developed a new electrochemical path that can transform CO2 into fuels and plastics. This new technology could drastically improve the way we capture and recycle carbon from the air.
“Today, it is technically possible to capture CO2 from air and, through a number of steps, convert it to commercial products,” said lead researcher Professor Ted Sargent. “The challenge is that it takes a lot of energy to do so, which raises the cost and lowers the incentive. Our strategy increases the overall energy efficiency by avoiding some of the more energy-intensive losses.”
Companies have been experimenting with direct-air carbon capture in recent history. One such company captures its CO2 by forcing air through a liquid alkaline solution wherein the CO2 dissolves and forms a substance called carbonate. Then, to complete the recycling process, the carbonate is then turned back into CO2 gas where it can then be used as the base for fuels and plastics after being mixed with other chemicals.
However, the researchers at the University of Toronto have devised a new recycling plan that utilizes an electrolyzer, a device that uses electricity to produce a chemical reaction, and has already been used to separate hydrogen from water.
“We used a bipolar membrane, a new electrolyzer design that is great at generating protons,” said co-lead author Geonhui Lee of the study’s paper, published in ACS Energy Letters. “These protons were exactly what we needed to convert the carbonate back into CO2 gas.”
The electrolyzer used in this experiment contains a silver-based catalyst that converts the produced CO2 into a gas mixture called syngas, which can be easily turned into a wide variety of other products like jet fuel and various plastics.
“This is the first known process that can go all the way from carbonate to syngas in a single step,” Sargent said. He notes that electrolyzers can be used to convert CO2 into other chemical building blocks, but never into carbonate.
“Once the CO2 turns into carbonate, it becomes inaccessible to traditional electrolyzers,” said co-lead author postdoctoral fellow Y. Chris Li. “That’s part of the reason why they have low yields and low efficiencies. Our system is unique in that it achieves 100% carbon utilization: no carbon is wasted. It also generates syngas as a single product at the outlet, minimizing the cost of product purification.”
The carbonate-to-syngas conversion was successful 35% of the time. More work will be needed to stabilize and scale up the process, but their current findings show a viable alternative to the current process of direct-air carbon capture.
“It goes a long way toward answering the question of whether it will ever be possible to use air-captured CO2 in a commercially compelling way,” Sargent concluded. “This is a key step toward closing the carbon loop.”
Image Credit: Marit Mitchell