MIT Makes Better Industrial Carbon Capture Technology But It is 100 Times More Costly Than Trees

MIT had made a solid-state faradaic electro-swing reactive adsorption system comprising an electrochemical cell that exploits the reductive addition of CO2 to quinones for carbon capture. The reported device is compact and flexible, obviates the need for ancillary equipment, and eliminates the parasitic energy losses by using electrochemically activated redox carriers. An electrochemical cell with a polyanthraquinone–carbon nanotube composite negative electrode captures CO2 upon charging via the carboxylation of reduced quinones, and releases CO2 upon discharge. The cell architecture maximizes the surface area exposed to gas, allowing for ease of stacking of the cells in a parallel passage contactor bed.

Above is a diagram of the new system, air entering from top right passes to one of two chambers (the gray rectangular structures) containing battery electrodes that attract the carbon dioxide. Then the airflow is switched to the other chamber, while the accumulated carbon dioxide in the first chamber is flushed into a separate storage tank (at right). These alternating flows allow for continuous operation of the two-step process.

Image courtesy of the researchers

An initial techno-economic analysis shows that the MIT solid state carbon capture systems can be economically feasible with costs ranging from $50–$100 per tonne CO2 depending on the feed concentrations and applications under consideration. This would theoretically be two to four times cheaper than other industrial carbon capture systems.

The lowest cost carbon capture systems are still trees, kelp and other biological methods. Biological carbon capture tends to price out at less than $1 per tonne of CO2.

This new way of removing carbon dioxide from a stream of air could provide a significant tool in the battle against climate change. The new system can work on the gas at virtually any concentration level, even down to the roughly 400 parts per million currently found in the atmosphere. Compared to other existing carbon capture technologies, this system is quite energy efficient, using about one gigajoule of energy per ton of carbon dioxide captured, consistently. Other existing methods have energy consumption which vary between 1 to 10 gigajoules per ton, depending on the inlet carbon dioxide concentration, Voskian says.

Most methods of removing carbon dioxide from a stream of gas require higher concentrations, such as those found in the flue emissions from fossil fuel-based power plants. A few variations have been developed that can work with the low concentrations found in air, but the new method is significantly less energy-intensive and expensive, the researchers say.

The cell is made of two cathode electrode substrates coated with a CO2-binding quinone–carbon nanotube (Q–CNT) composite sandwiching an anode electrode substrate coated with a ferrocene–CNT (Fc–CNT) composite, with separator membranes between the electrodes. This cell architecture is employed to maximize the CO2-binding surface area of the cell exposed to gas flow in a parallel passage adsorbent contactor design where stacks of these cells form parallel gas channels. The Fc–CNT electrode serves as an electron source and sink for the reduction and oxidation, respectively, of the Q–CNT electrodes to regulate the uptake and release of the CO2. Wetting of porous non-woven carbon fiber mats used as the electrode substrates by a room temperature ionic liquid (RTIL) electrolyte enables effective ionic currents to pass through the electrolyte on activation and deactivation of the electrodes, and permits the diffusion of CO2 into the electrolyte-wetted cathodes during capture.

MIT researchers demonstrated the capture of CO2 both in a sealed chamber and in an adsorption bed from inlet streams of CO2 concentrations as low as 0.6% (6000 ppm) and up to 10%, at a constant CO2 capacity with a faradaic efficiency of over 90%, and a work of 40–90 kJ per mole of CO2 captured, with great durability of electrochemical cells showing less than 30% loss of capacity after 7000 cylces.

15 thoughts on “MIT Makes Better Industrial Carbon Capture Technology But It is 100 Times More Costly Than Trees”

  1. The 2nd link points to the paper, which in the Conclusions section states the same sentence that was quoted by Brian: “… can be economically feasible with costs ranging from $50–$100 per tonne CO2 …”.

    I read that as “can be economically feasible, and will cost $50–$100 per tonne CO2″. But it can also be interpreted as “can be economically feasible if it will cost $50–$100 per tonne CO2″. So depends on how you want to interpret.

    They say that the analysis is not reported, so we can’t tell which interpretation is correct. edit: However, the required cost for economic feasibility doesn’t depend on the CO2 capture technology, so assuming they were analyzing this particular technology, I think the first interpretation is more likely.

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  2. Don’t know, but the article does specify 1G-joule per ton of CO2, which would come in around $30-$40 per ton for the electricity used and producing about 250kg of CO2 if the electricity is made with coal power. Presumably they could use non-fossil-fuel generated power…

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  3. Here is a better explanation of what took place, the CO2 used is more complex from an unspecified source and the wells of a geothermal plant if I understand right. The results still seem promising.

    “During the original CarbFix injection, water was pumped from well HN-01, and co-injected with CO2 into well HN-02. This occurred in two phases: first, starting in late January 2012, 175 t of pure CO2 was injected together with the water17. This phase ran continuously until 9 March 2012; the second phase was from mid-June to early August 2012, in which 73 t of a gas mixture containing 75 mol% CO2, 24 mol% H2S and 1 mol% H2 was injected. The plume of injected material was monitored at the closest monitoring well HN-04, 500 m from HN-02 at depth. Changes in DIC, pH and tracer concentration were observed starting within 2 weeks of injection. Tracer injection suggests that ~95 ± 3% of the injected carbon was mineralised within 2 years5,8. The rapid conversion of the dissolved CO2 to carbonate minerals is likely due to the novel method of dissolved CO2 injection, the rapid dissolution rate of basalt, providing the necessary cations, such as Ca, Mg or Fe, the mixing of the injected water with alkaline groundwaters and the dissolution of pre-existing carbonates at the onset of CO2 injection5. Analysis of solids recovered from the monitoring well and pumps shows the precipitation of calcite, but no aragonite precipitation5.

    https://www.nature.com/articles/s41467-019-1

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  4. The article you link to indicates that the CO2 comes from the geothermal water. But I’m prepared to believe that the writer was just illiterate which seems to be a common problem with journalists.

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  5. Maybe I don’t understand you right , they are talking here about CO2 emissions from conventional thermal plants like coal. The choice of the word wells is misleading

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  6. Wait, if you are reinjecting geothermal fluids back into the reservoir after extraction and turbine spinning, why would you need to separate and then reintegrate the CO2 into the returning fluid? Wouldn’t the uncaptured CO2 in the steam sent through the turbine still be present in the collected water after the steam condenser?

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  7. Umm, where is the price estimate (of $50-100 per tonne) given? A quick look through the linked material turned up those numbers, but as the cost the process needed to have, in order to be economic. Not the price it has now, or could have. Where do I look for that?

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  8. The only application I can see at these prices is that US Navy scheme of using nuclear power to make synthetic fuel at sea so they can keep their jets in the air during a war.

    In that case you aren’t competing with trees or kelp or concentrated coal station exhaust, you are competing with loading fuel in San Diego and sending it, by ship, through a hostile ocean (assuming there is a war on) to the actual battle zone of say the Bay of Biscay (assuming the war is against France) and then transferring it from ship to ship under combat conditions. That adds a lot of zeros to the price that on-site, nuclear powered synthesis can avoid.

    Every other application has access to large scale, cheap, land based, alternatives to grabbing your CO2 out of the air.

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  9. The future of Carbon capture is CarbFix, pretty sure that more variations are coming, maybe instead of pumping the carbonated water down a 3000 ft wells, mining the the basalt or maybe other types of rock as well, completing the reaction on the surface and doing something useful with the mineralized CO2, like building the Great underwater ocean melting blocking Antarctic wall!

    “As the power plant pumps up the volcanic water to run the turbines that provide heat and electricity to Reykjavik, the scientists capture the CO2 emitted from the plant’s steam and liquifies it into condensate. Then, they dissolve it in large amounts of water. This process, as CarbFix project director Edda Sif Aradottir points out in a press statement, is basically how you make soda water.

    The water is then piped to nearby wells, where the scientists inject it into the basalt rock 3,300 feet under the ground. When the water hits the rock, it fills its cavities and begins solidifying, thanks to the chemical reaction when CO2 interacts with calcium, magnesium, and iron—all present in the basalt.
    Before long, that injected CO2 becomes mineralized and safely stays underground forever. (Well, hopefully; the last eruption at the volcano under Hellisheidi happened 1,000 years ago.)”

    https://www.popularmechanics.com/science/green-tech/a27410266/iceland-fighting-climate-change-carbon-storage/

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  10. > costs ranging from $50–$100 per tonne CO2 depending on the feed concentrations and applications under consideration.

    For comparison, bulk methane from fossil sources sells for ~150 $/ton, and that’s considered cheap.

    I still expect that methane from CO2 capture should be more expensive (methane from atmospheric CO2 > methane from concentrated CO2 streams > bulk methane). I guess a big part of synthetic methane’s cost would be the energy cost for making hydrogen (presumably from water). It looks like CO2 capture will be a smaller part of the cost than I previously thought.

    > Biological carbon capture tends to price out at less than $1 per tonne of CO2.

    This is also important, and I expect biomethane cost to fit between methane from concentrated CO2 streams and bulk methane from fossil sources. Even if biocapture is closer to 30 $/ton as NewtonPulsifer says, that’s still cheaper.

    Finally, I’m skeptical of the price and scalability of their CNT-based electrodes. But the CNTs only serve as a porous structural support with good conductivity, so they may find cheaper alternatives. Some sort of nanostructured nickel maybe?

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