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Carbon Capture and Sequestration

Published on October 28, 2021

Gridling’s Perspective: This series explores nascent smart city technologies changing the future of infrastructure.

By Alex Nittel

Going forward, preventing carbon from getting into the air and removing it from the air will be crucial for climate change mitigation.

To avert catastrophic temperature increase due to global warming, something big needs to change. This century, we need to reduce CO2 emissions as well as the concentration of carbon in the atmosphere. One method of doing this is to capture CO2 at point sources, such as natural gas fired power plants, and then inject the CO2 into rock formations deep underground, where it will be permanently sequestered.


Sounds novel? Maybe not. You may be surprised to find out that industry has substantial experience with injecting CO2 deep underground. Since the 1970’s, oil companies have been doing something called Enhanced Oil Recovery, or EOR. In EOR, CO2 is captured from fossil fuel processing and point sources, such as powerplants, and then injected into rock formations near oil wells.[1] The CO2 forces nearby, inaccessible, oil into the well, where it can be pumped out. But if more CO2 goes into the ground than comes out in the oil, the oil becomes carbon neutral, or possibly even a net carbon sink.


Being carbon neutral, with respect to oil is great – things are no worse than when they started pumping the oil. But to meet climate change mitigation goals, we need to go one step further: we need to remove CO2 from the atmosphere. Fortunately, there are some cutting-edge companies tackling this challenge. An emerging technology in this field is Direct Air Capture, or DAC. DAC plants remove CO2 from ambient air, making it available for a variety of uses. One is to inject it into rock formations deep underground, where it will stay. It can also be used for EOR.


There are a bunch of creative uses for this carbon. Through a series of proprietary chemical processes, DAC plants can take CO2 from the atmosphere, and, using renewable energy, electrolyze water into oxygen and hydrogen. These constituent parts can be reacted into synthetic hydrocarbons.

These synthetic hydrocarbons can be used for a number of different purposes. For one, they can make something called ‘electrofuels’ which can be used as a ‘drop-in’ replacement for fossil fuels. This makes particular sense for aviation fuel, which is hard to decarbonize. The same goes for other long-distance transportation fuels, such as those used in maritime and trucking applications.[2] The transition to electric vehicles continues and ambitious goals abound, but before widespread adoption occurs, the existing gasoline and diesel infrastructure can be made sustainable with ‘drop-in’ electrofuels. This is especially important as some barriers to electric vehicles have yet to be resolved, such as lithium mining, which can be environmentally harmful.

Synthetic hydrocarbons can also be used to make various commodities. There is widespread support for phasing out fossil fuels, but going forward, chemical products made with processed fossil fuels, such as plastics, will still be in demand. Synthetic hydrocarbons can be engineered to create materials, like plastics. The byproducts of DAC have applications that include steelmaking, in which the captured carbon is added to iron. Additionally, one popular use for captured carbon is to use it in the cement making process. Cement, augmented with captured carbon, has been shown to be stronger than regular cement.[3]


One might wonder if all this is necessary. Why not just plant trees to take CO2 out of the atmosphere? The truth is that, on a per unit area, DAC plants are much more space efficient than trees.[4] Occidental Petroleum’s “Permian Basin CO2 storage infrastructure has the capacity to store about 150 billion tons of CO2 safely and permanently underground; that’s the equivalent of 300 trillion trees.”[5] Trees can still play a role with “Biomass Energy with Carbon Capture,” or BECCS. According to the United Nations Economic Commission for Europe, “In BECCS, CO2 is taken out of the atmosphere by vegetation, then recovered from the combustion products when the biomass is burnt. In DACCS [Direct Air Capture and Carbon Sequestration], CO2 is captured directly from the air. In both cases, the captured CO2 is compressed and then injected into porous rock layers a kilometre or more under- ground, beneath impermeable rocks that will keep it in place for tens of thousands to millions of years.”[6] In addition, “BECCS and DACCS can in effect capture CO2 from the air from any fuel source anywhere in the world. BECCS is expected to be cheaper, at maybe $50-200/tCO2 removed and stored, while DACCS might be roughly twice the cost. But DACCS is able to remove large amounts of CO2 from the atmosphere without the demands on natural systems required by growing biomass.”[7]


The two biggest players in DAC are Climeworks and Carbon Engineering.[8] Both have built pilot plants, which they hope will showcase DAC technology and encourage investment from private industry and governments. Already, there are other pilot projects emerging, including some that transport captured CO2 by ship to depleted oil fields, where it can be injected for permanent sequestration.[9] All this is predicated on there being cheap and abundant clean energy. DAC plants need to run on renewable energy; otherwise, running on fossil fueled energy they would not be reducing the amount of CO2 in the atmosphere.


There’s one more piece to the puzzle, though. Financial incentives to sequester carbon are needed for carbon capture tech to reach scale, as cost remains a barrier. Ideally, this would be accomplished via a price on carbon, through a carbon tax or a cap and trade system. The aforementioned options are politically controversial and divisive, thus making carbon capture more likely to be incentivized through alternative means. Tax credits, such as the 45Q credit, are one option.[10] Another is regulation encouraging carbon capture which could be enacted under the Clean Air Act.[11] In California there is the Low Carbon Fuel Standard; this could be a model for the rest of the country.[12]


With carbon capture technologies, such as DAC, becoming more and more mature, it is reasonable to be cautiously optimistic that mitigating the worst effects of climate change is within reach.

Alex Nittel has been providing research support for Gridling Global since 2018.

[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]

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