A pair of engineers from the Massachusetts Institute of Technology (MIT) have developed a “revolutionary” new technique of pulling carbon dioxide (CO2) from the air (or a gas stream) and turning it into usable carbon.
In a research paper published in the journal Energy and Environmental Science titled “Faradaic electro-swing reactive adsorption for CO2 capture”, Sahag Voskian and T. Alan Hatton detail a “compact electrochemical device for CO2 capture” that is cheaper, more efficient, and more versatile than existing methods.
Speaking to MIT News, Voskian called it a "revolutionary" process that could take place under ambient conditions, work with concentrations of CO2 ranging from that of the gas flues from a power plant to the amount present in the air, and that can be scaled up simply by adding electrodes to the design.
The device is essentially a battery with a stack of electrodes coated with polyanthraquinone, through which gases containing CO2 can be passed. The coating allows the capture of carbon dioxide at any level of concentration, be it from the air or from flue gas streams of the kind found in power plants, using a process known as Electro-Swing Adsorption. This capture takes place during the charging cycle of the battery, while the discharge cycle creates a stream of pure CO2—which can be utilised in commercial applications like the carbonation of drinks or the enrichment of crops in greenhouses.
One of the problems with existing Carbon Capture and Sequestration (CCS) technologies is that they often perform poorly in terms of energy efficiency and practicality when to pulling CO2 from mixtures where it exists in low concentrations (like the air).
Significantly, the MIT engineers say their method would work at the 400 particles per million (ppm) level of CO2 currently found in earth’s atmosphere as well as at concentrations as low as 0.6 per cent.
The paper says their battery is good for over 7,000 cycles of charging and discharging (with scope to scale this up as the research continues) and that it can be easily applied into existing processes in a plug-and-play fashion thanks to its and-play design.
Voskian, who is a postdoc at MIT, shared an animation of the process on Vimeo which you can watch below.
Voskian and Hatton (the Ralph Lanau Professor of Chemical Engineering) plan to make a commercial venture out of their method. The research, supported by an MIT Energy Initiative Seed Fund, is set to make its way to a company started by the two engineers, named Verdox, with plans for a pilot-scale plant within two years.
Such systems still require energy to pull off—Voskian says this method uses about one gigajoule of energy per tonne of carbon dioxide. “Compared to other existing carbon capture technologies, this system is quite energy efficient, using about one gigajoule of energy per ton of carbon dioxide captured, consistently. Other existing methods have energy consumption which vary between 1 to 10 gigajoules per ton, depending on the inlet carbon dioxide concentration.”
The viability of such techniques to make an impact on global warming as an outcome of CO2 emissions will depend on the types of energy sources used to fuel them.
According to Canada’s federal government department on natural resource's online tool to calculate energy efficiency, one gigajoule is equivalent to 277.8 kilowatt hours (kWh), which is the amount of energy present in 0.17 barrels of oil—enough to boil 1,000 pots of coffee.
For perspective, in 2017, the United States alone produced 5.14 billion metric tons of CO2 emissions. CCS technology cannot hope to match the entire carbon output of the world—something that Greta Thunberg pointed out in the short film Nature Now, arguing instead for natural climate solutions such as afforestation.
However, the paper claims that the costs of sequestering CO2 with this technique would be low, hovering between $50-100 per ton of carbon. This spells hope that such techniques could find commercial viability, increasing their application and hopefully improving the efficiency of existing CO2 emitters.
A 2018 McKinsey report identified multiple avenues where CCS technologies could be used to fulfil the growing technological and commercial applications of carbon dioxide—from the creation of fuels to the enrichment of concrete. The report highlighted the high cost of carbon sequestration ($80 per ton, at the time), predicting that this would halve in the coming years.
According to the recently released report, “Carbon Capture and Sequestration - Global Market Outlook (2017-2026)”, the market for carbon capture technologies will be worth $16.09 billion by 2026.
