For example, in an overview article on December 4, 2017, "Humanity’s fight against climate change is failing. One technology can change that," Rathi notes that before starting a year of research and writing on the topic, he was skeptical of carbon capture and storage could be cost-effective. However, he also notes that this technology may both be necessary and possible.
On the issue of necessity, Rathi writes: "The foremost authority on the matter, the Intergovernmental Panel on Climate Change, has modeled hundreds of possible futures to find economically optimal paths to achieving these goals, which require the world to bring emissions down to zero by around 2060. In virtually every IPCC model, carbon capture is absolutely essential—no matter what else we do to mitigate climate change." (Rathi and David Yanovsky offer an interactive game to drive home this point here.)
On the issue of possibility, the evidence is scattered, and still more at the proof-of-concept stage than at a full-fledged and ongoing industry. But some of these fledgling projects are intriguing. For example, Rathi discusses an operation in Iceland (discussed in more detail in an earlier article) which issues geothermal heat to capture carbon dioxide and inject it underground in a location where it combines with minerals to form solid rock--an operation which is an overall net subtraction of carbon from the atmosphere. Rathi notes:
"Since 2014, the plant has been extracting heat from underground, capturing the carbon dioxide released in the process, mixing it with water, and injecting it back down beneath the earth, about 700 meters (2,300 ft) deep. The carbon dioxide in the water reacts with the minerals at that depth to form rock, where it stays trapped. ... In other words, Hellisheidi is now a zero-emissions plant that turns a greenhouse gas to stone. ... Critics laughed at those pursuing a moonshot in “direct-air capture” only a decade ago. Now Climeworks is one of three startups—along with Carbon Engineering in Canada and Global Thermostat in the US—to have shown the technology is feasible. The Hellisheidi carbon-sucking machine is the second Climeworks has installed in 2017. If it continues to find the money, the startup hopes its installations will capture as much as 1% of annual global emissions by 2025, sequestering about 400 million metric tons of carbon dioxide per year."In another article, Rathi discusses a plant which generates electricity from natural gas near Houston, in "A radical startup has invented the world’s first zero-emissions fossil-fuel power plant" (December 5, 2017). The process involves using "supercritical" carbon dioxide, under high termperatures and pressures. He writes:
"In the end, the Allam cycle is only slightly more efficient than typical combined-cycle systems. But it has the major added benefit of capturing all potential carbon dioxide emissions essentially for free. ... Beyond the greenhouse-gas effect, carbon dioxide has some fascinating properties. At high pressure and temperature, for instance, it enters a state of matter where it’s neither a gas nor a liquid but has properties of both. It’s called a “supercritical fluid.” If you’ve ever had decaf coffee, you’ve likely been an unwitting customer of supercritical carbon dioxide, which is often used to extract caffeine from coffee beans with minimal changes to the taste."China, which leads the countries of the world in carbon emissions, has been experimenting with carbon capture and storage, without yet making a strong commitment to the technology, as Rathi explains here (and a 2015 report from the Asia Development Bank discusses here).
There are a variety of new projects and possible innovations either to capture carbon from emissions at lower cost, or to turn carbon dioxide into solids like soda ash, and other approaches. Carbon capture and storage isn't yet a proven large-scale technology, but it's a promising one.
For some previous posts on this topic, with links to various reports and articles, see:
- "Carbon Capture and Storage: An Update" (December 24, 2013)
- "Carbon Capture and Storage: No Stone Unturned" (July 7, 2016)
