The Economist wrote about new “air capture” machines which can be used to scrub carbon dioxide from air. A form of the technology is in use — submarines and spacecraft currently remove carbon dioxide from in-cabin air. Supports of air capture see it as a way to remove bulk amounts of carbon dioxide from the earth’s atmosphere; the CO2 captured could then be sold for industrial use, stored underground, or in turn used to generate energy. (See a related article by The Economist on the state of Carbon Capture and Sequestration pilot projects).
According to The Economist, a few different methods for air capture are being explored. “In each case air is brought into contact with a “sorbent” material, which binds chemically with the carbon dioxide. The efficiency of this process depends on the surface area of the sorbent, and an easy way to increase the surface area is to spray a liquid sorbent into the air as a fine mist. At PARC, researchers propose building towers several metres high through which the air would be wafted, coming into contact with a sorbent mist. Having absorbed CO2 from the air, the liquid would drain into a chamber where the gas would be extracted from the sorbent by a series of chemical reactions, or by applying an electric current, depending on the system’s design. The sorbent can then be recycled, and the CO2 compressed into liquid form for removal.”
Air capture machines are electrically powered, so they also raise the question: Can they capture more CO2 than they will generate through their own operation? This is particularly important if they are to be rolled-out at any mass scale. Global Research Technologies (GRT) estimates that the CO2 emissions for each machine would be just 5 percent of the CO2 captured over the life of the machine, so they could significantly reduce CO2 amounts beyond the amount they generate. The market cost of any industrial CO2 that could be collected by the machines could also eventually off-set the costs of the technology if the price of air-capture related technologies came down enough.
Air capture machines could also be used to create energy. CO2 pulled from the atmosphere could be combined with hydrogen, leading to the production of synthetic hydrocarbon fuels. While the costs remain prohibitively high for hydrocarbon fuels generated in this manner (4-5 USD per gallon), connecting air-capture systems with wind turbines could be a way to take advantage of the extra energy created by wind farms in off-peak hours. In this scenario, wind farms would run the air capture systems.
The Economist relates air capture technologies to previous scientific breakthroughs that had widespread impact. “In 1909 Fritz Haber, a German chemist, discovered a new way to combine nitrogen from the air with hydrogen to produce ammonia. Previously, this was known to be technically possible, but the process was hopelessly inefficient. Haber’s new process, subsequently scaled up by Carl Bosch, meant that ammonia could be produced in industrial quantities, for use in both agricultural fertiliser and explosives—with momentous historical consequences. Haber was awarded the Nobel prize in chemistry for producing “bread from the air”. Ammonia synthesised using the Haber-Bosch process underpinned the “green revolution” in the second half of the 20th century and its associated population boom; today it sustains one-third of the world’s population. A century later, might scientists tinkering with another apparently inefficient process be on the verge of another unexpected breakthrough?”