A study by Mark Z. Jacobson, professor of civil and environmental engineering at Stanford University, suggests that carbon capture technologies are inefficient and increase air pollution. His open-access paper is published in the journal Energy and Environmental Science.

All sorts of scenarios have been developed under the assumption that carbon capture actually reduces substantial amounts of carbon. However, this research finds that it reduces only a small fraction of carbon emissions, and it usually increases air pollution. Even if you have 100 percent capture from the capture equipment, it is still worse, from a social cost perspective, than replacing a coal or gas plant with a wind farm because carbon capture never reduces air pollution and always has a capture equipment cost. Wind replacing fossil fuels always reduces air pollution and never has a capture equipment cost.

—Mark Jacobson

Jacobson, who is also a senior fellow at the Stanford Woods Institute for the Environment, examined public data from a coal with carbon capture and use (CCU) plant and a synthetic direct air carbon capture and use (SDACCU) plant for the equipment’s ability, alone, to reduce CO₂. In both plants, natural gas turbines power the equipment.

He calculated the net CO₂ reduction and total cost of the carbon capture process in each case, accounting for the electricity needed to run the carbon capture equipment, the combustion and upstream emissions resulting from that electricity, and, in the case of the coal plant, its upstream emissions.

(Upstream emissions are emissions, including from leaks and combustion, from mining and transporting a fuel such as coal or natural gas.)

This research also looked at the social cost of carbon capture—including air pollution, potential health problems, economic costs and overall contributions to climate change—and concluded that those are always similar to or higher than operating a fossil fuel plant without carbon capture and higher than not capturing carbon from the air at all.

Jacobson examined several scenarios to determine the actual and possible efficiencies of these two kinds of plants, including what would happen if the carbon capture technologies were run with renewable electricity rather than natural gas, and if the same amount of renewable electricity required to run the equipment were instead used to replace coal plant electricity.

While the standard estimate for the efficiency of carbon capture technologies is 85-90%, neither of these plants met that expectation. Even without accounting for upstream emissions, the equipment associated with the coal plant was only 55.4% efficient over 6 months, on average.

With the upstream emissions included, Jacobson found that, on average over 20 years, the equipment captured only 10-11% of the total carbon dioxide equivalent emissions that it and the coal plant contributed.

The air capture plant was also only 10-11% efficient, on average over 20 years, once Jacobson took into consideration its upstream emissions and the uncaptured and upstream emissions that came from operating the plant on natural gas.

Due to the high energy needs of carbon capture equipment, Jacobson concluded that the social cost of coal with carbon capture powered by natural gas was about 24% higher, over 20 years, than the coal without carbon capture.

If the natural gas at that same plant were replaced with wind power, the social cost would still exceed that of doing nothing. Only when wind replaced coal itself did social costs decrease.

For both types of plants this suggests that, even if carbon capture equipment is able to capture 100% of the carbon it is designed to offset, the cost of manufacturing and running the equipment plus the cost of the air pollution it continues to allow or increases makes it less efficient than using those same resources to create renewable energy plants replacing coal or gas directly.

Not only does carbon capture hardly work at existing plants, but there’s no way it can actually improve to be better than replacing coal or gas with wind or solar directly. The latter will always be better, no matter what, in terms of the social cost. You can’t just ignore health costs or climate costs.

There is a lot of reliance on carbon capture in theoretical modeling, and by focusing on that as even a possibility, that diverts resources away from real solutions. It gives people hope that you can keep fossil fuel power plants alive. It delays action. In fact, carbon capture and direct air capture are always opportunity costs.

—Mark Jacobson

Resources

• Mark Z. Jacobson (2019) “The Health and Climate Impacts of Carbon Capture and Direct Air Capture” Energy Environ. Sci. doi: 10.1039/C9EE02709B