Finding technology to shift carbon dioxide (CO₂), the most abundant anthropo- genic greenhouse gas, from being a climate change challenge to being a valuable commodity has long been a dream of many scientists and government officials.

To this end, a team of chemists say they have developed a way to economically convert atmospheric CO₂ directly into highly valued carbon nanofibres for industrial and consumer products.

“We have found a way to use atmospheric CO₂ to produce high-yield carbon nanofibres,” says George Washington University Department of Chemistry academic Professor Stuart Licht, who leads the research team. The team also includes postdoctoral fellow Jiawen Ren and graduate student Jessica Stuart.

He explains that nanofibres are used to make strong carbon composites, such as those used in the Boeing Dreamliner, as well as in high-end sports equipment, wind turbine blades and other products.

Previously, the researcher team made ferti- liser and cement without emitting CO₂. Currently, the researchers are seeking to shift CO₂ from being a global-warming problem to being a feedstock for the manufacture of in-demand carbon nanofibres.

Licht calls his approach “diamonds from the sky.” This refers to carbon being the material that diamonds are made of, and also hints at the high value of the products, such as the carbon nanofibres that can be made from atmospheric carbon and oxygen.

He says that, because of its efficiency, this low-energy process can be run using only a few volts of electricity, sunlight and a significant amount of CO₂.

Licht explains that, at its root, the system uses electrolytic syntheses to make the nanofibres. CO₂ is broken down in a high-temperature electrolytic bath of molten carbonates at 750 °C.

“Atmospheric air is added to an electrolytic cell. Once there, the CO₂ dissolves when subjected to the heat and direct current through electrodes of nickel and steel. The carbon nanofibres build up on the steel electrode, where they can be removed.”

He notes that, to power the syntheses, heat and electricity are produced through a hybrid and extremely efficient concentrating solar-energy system. Licht points out that the system focuses the sun’s rays on a photovoltaic solar cell to generate electricity and on a second system to generate heat and thermal energy, which raises the temperature of the electrolytic cell.

He further estimates electrical energy costs of this “solar thermal electrochemical process” to be around $1 000/t of carbon nanofibre product, which means the cost of running the system is hundreds of times less than the value of the product output.

“We calculate that, with a physical area less than 10% the size of the Sahara Desert, our process could remove enough CO₂ to decrease atmospheric levels to those of the preindustrial revolution within ten years,” Licht contends.

He emphasises that the system is currently experimental, and his biggest challenge will be to ramp up the process and gain experience to make consistently sized nanofibres.

“We are scaling up quickly and soon should be . . . making tens of grams of nanofibres an hour,” Licht states.