It is technically feasible to build machines to extract and store CO2 from power plant and industrial smokestacks. We could also build machines to capture CO2 directly from the atmosphere. As we’ll see, however, there is no currently available path for carbon capture that can scale to cut even a small amount of the current 50.8 billion tons of CO2 equivalent emissions necessary for a 2° C or less rise in global temperature.
REFORESTATION. Trees and plants capture CO2 in the atmosphere and use it to grow. Reforestation is a popular topic; even President Trump committed to planting a trillion trees earlier this year. However, we are actually losing millions of acres annually to deforestation, logging, crop shifts, urbanization, etc. Witness the fires in the Amazon and the terrible recent tragedy in Australia where 42 million acres burned. Scientists estimate that if we begin to plant more trees than we lose, we could reduce the carbon in the atmosphere by 25%, but we’d have to immediately start planting enough trees to cover an area the size of the entire United States. And we could never cut them down again.
DIRECT AIR CAPTURE. The atmosphere is now 0.04% CO2 (400 parts per million). Going from 0.02% to 0.04% in the last 100 years has had the outsized effect of trapping heat in the atmosphere that would normally have been released into space. We would have to build machines to chemically process a large percentage of atmospheric air to remove and then store the CO2. A current estimate is that 30,000 large scale carbon capture units would be required, but that would use 300 exajoules of power, about half of worldwide energy demand today. If we used fossil fuels to make that power, what’s the point?
CARBON CAPTURE AT INDUSTRIAL SOURCES. It is technically feasible for coal plants to scrub the CO2 out of their emissions and bury it deep underground, but it is prohibitively expensive and requires 30% of the energy load of the plant. Coal plants, which are mostly unprofitable already, don’t do it. There are eighteen major carbon capture and storage projects operating around the world, sequestering 40 million tons of CO2 per year (less than 0.1% of global emissions). However, most of the captured carbon is injected back into oil fields to make more fossil fuel. The Northern Lights project, a collaboration between Equinor, Total and Shell aims to sequester millions of tons of industrial liquified CO2 under the sea, but this project’s capacity is only 1.5 million tons of CO2 per year (less than 0.001% of global emissions).
Reforestation is vital both for the atmosphere and for plant and animal biodiversity. But economically viable carbon capture at industrial plants or directly from the atmosphere doesn’t exist and is not scalable. The only scalable path to meet our climate goals is to make almost all electricity with renewable sources like wind, hydro and solar and use that energy to power transportation and buildings. And without a price on carbon, there will never be a financial incentive for emitters to reduce carbon emissions until it is too late.