That standoff has refocused attention on methods for removing carbon from the atmosphere. Approaches that can remove carbon dioxide from the air and sequester it away (as trees do) remain mostly at an experimental stage. The biggest challenge in such approaches is that even though 400 ppm of carbon dioxide in the atmosphere poses a risk to the climate, it’s not sufficiently concentrated to make capturing it from the air economically appealing in most cases.
To remove just 400 tons of carbon dioxide from the atmosphere would require one million tons of air to be processed. This would generally entail moving the air, which requires energy and may entail more emissions.
Carbon Capture, Utilization, and Storage
Another approach is beginning to gain momentum. Y Combinator, a startup accelerator that has spawned several successful companies, has shifted its focus to solutions like carbon capture, utilization, and storage (CCUS). These approaches typically involve methods of capturing carbon dioxide from the flue gas of power plants, and either storing it or recycling it into products like fuels, chemicals, or plastics.
Of all the global sources of carbon dioxide emissions, power plants are the most attractive for CCUS. Unlike automobiles, which globally represent something like a billion individual sources of carbon dioxide, power plants represent large, concentrated sources of carbon dioxide emissions.
Cost-effective methods for scrubbing these emissions and preventing them from entering the atmosphere could substantially slow the rise of atmospheric carbon dioxide. The challenges in CCUS are to find approaches that are economically viable, and that manage to store or otherwise reuse the carbon dioxide in a way that reduces the overall carbon dioxide footprint.
The best technical approach for sequestering the carbon dioxide for extended periods would be to simply capture it and inject it into underground caverns. But this approach requires additional power inputs to compress and transport the carbon dioxide and isn’t necessarily economically viable. While technically possible, it could add significantly to the cost of the power produced since the carbon dioxide isn’t being economically utilized.
But economical approaches also need to sequester carbon dioxide. Two major uses of carbon dioxide are for carbonation in soft drinks, and for use in enhanced oil recovery. These are profitable uses of carbon dioxide, but neither of these outlets would lead to anything more than transient storage.