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Effective carbon sequestration methods and how we can deploy them to save ourselves

Image credit: Will Elder, NPS

Darko Savic
Darko Savic Sep 01, 2020
What are currently the most promising methods of pulling carbon out of the air? How can we deploy/finance them en masse?

There is a growing consensus among experts that to avoid catastrophe, we must put all our efforts into reducing CO2 emissions. Even so, that might not be enough anymore. If we are to limit atmospheric warming to a level below which irreversible changes become inevitable we'll need to actively remove CO2 from the air, and fast too.

There are basically two variables we could work on adjusting:
  1. the amount of heat energy that is reaching the earth from the sun
  2. the quantity of greenhouse gasses in the atmosphere to trapt that heat

Here we talk about the 2nd variable - the current cutting edge carbon sequestration technology.

How can we deploy the best solutions in significant enough numbers to save life on our planet before things run out of hand?


Creative contributions

Carbon sequestration using E.coli as a biological carbon capture device

Subash Chapagain
Subash Chapagain Oct 19, 2020
Among the major technologies present today for carbon sequestration are the physical and chemical processes. An alternative approach to use the ability of living organisms to perform this reaction biologically has been tried and tested, at least experimentally. In very promising research, a group of scientists at Dundee University have developed an ingenious process to use the gut inhabiting E.coli bacterium to work as a very efficient carbon capture device. So, here is how the biological carbon-capturing works:

E.coli is a bacterium that has the ability to grow in the complete absence of oxygen. For its oxygen-free living, E.coli expresses a special metal-containing enzyme called formate hydrogen lyase (FHL). FHL enzyme normally oxidizes formic acid to carbon dioxide, and couples this reaction directly for reducing protons (basically Hydrogen atoms) to form molecular hydrogen (H2 as we know it). What the group in this study did was that they unlocked the reverse reaction of FHL. It has been reported that FHL can function as a highly efficient hydrogen-dependent carbon dioxide reductase ( an enzyme that reduces) when gaseous CO2 and H2 are placed under high pressure (up to 10 atmospheric pressure). When live, intact whole cells of E.coli were used, the pressurized system was found able to convert 100% of gaseous CO2 to formic acid. More than 500 millimolar (mM) formate was observed to accumulate in a solution. Using this reverse reaction has the promise of exploiting the model E.coli system as an exciting and effective carbon capture technology. The reaction happens in a short period of time, a few hours, and can take place in ambient temperatures.

If the system could be fully optimized and developed further to model a ‘microbial cell factory’ that could mop up carbon dioxide from different industries, it could be one of the modern breakthroughs in microbial technology with a large impact. What is even more commendable is the fact that the end product, formic acid also has many industrial uses. It can be used to prepare preservatives and antibacterial agents in livestock feed. It can also be used as a coagulant in the production of rubber and its salt form as a de-icer for airport runways.

[1]Roger, M., Brown, F., Gabrielli, W., & Sargent, F. (2018). Efficient Hydrogen-Dependent Carbon Dioxide Reduction by Escherichia coli. Current Biology, 28(1), 140-145.e2. https://doi.org/10.1016/j.cub.2017.11.050

Artificial Photosynthesis devices

Subash Chapagain
Subash Chapagain Dec 02, 2020
In a very recent paper published in Nature Energy, scientists from the University of Cambridge have reported a prototypical device for artificial photosynthesis that takes CO2, water and sunlight as its ingredients and produces formic acid as the end product that can be stored as fuel. Formic acid thus produced can be directly used as an energy source or be converted into hydrogen which is another clean energy fuel.

Picture from the paper : the artificial Z-scheme used for photosynthesis described for this device

Mimicking the natural Z-scheme of photosynthesis, the researchers have built a photocatalyst sheet that performs photosynthetic CO2 reduction reaction (CO2RR) to form formate (HCOO-), using water as the electron donor. The monolithic device is composed of specially synthesized semiconductor powders that enable electron interactions and oxidation reactions to occur when the sunlight hits the sheet in water, cobalt-based catalyst helping the system. The device as of now is limited in size (20 square centimetres), but the scientists behind its invention are positive about its scalability.

Key features of this device:
  • high selectivity for formate (97±3%)
  • high stability during the light reaction without sacrificial reagents
  • easy to scale up, possibly cost-effective
  • no unwanted byproducts, eliminating the burden of waste removal

[1]Wang, Q., Warnan, J., Rodríguez-Jiménez, S. et al. Molecularly engineered photocatalyst sheet for scalable solar formate production from carbon dioxide and water. Nat Energy 5, 703–710 (2020). https://doi.org/10.1038/s41560-020-0678-6

Elon Musk's 100M prize to tackle this problem

Darko Savic
Darko Savic Mar 17, 2021
Elon Musk is pledging 100M for the best new solution to the problem of CO2 buildup in the atmosphere. The objective of the prize is to inspire and help scale efficient solutions to collectively achieve the 10 gigatons per year carbon removal target by 2050.

Team registration opens on Earth Day, April 22nd, 2021. The competition will last for 4 years until April 22nd, 2025.

To win the competition, teams must demonstrate a rigorous, validated scale model of their carbon removal solution, and further must demonstrate to a team of judges the ability of their solution to economically scale to gigaton levels.

Teams can submit entries across natural, engineer, and hybrid solutions. Judges in the competition will evaluate the teams based upon four basic criteria:

  • A working carbon removal prototype that can be rigorously validated and capable of removing at least 1 ton per day.
  • The team’s ability to demonstrate to the judges that their solution can economically scale to the gigaton level.
  • The main metric for this competition is fully considered cost per ton, inclusive of whatever considerations are necessary for environmental benefit, permanence, any value-added products; and
  • The final criteria is the length of time that the removed carbon is locked up for. A minimum goal of 100 years is desired.


Povilas S
Povilas Sa month ago
That's big news. Best way to move things forward

Using cyanobacterium to sequester carbon dioxide

Subash Chapagain
Subash Chapagain Oct 24, 2020
Cyanobacteria are a group of bacteria that are photosynthetic. They grow in very large colonies and they are among the oldest known fossils. They are one of the largest groups of bacteria on earth, and since they are photo-autotrophic, they can be used to sequester carbon dioxide, some promising studies have shown.

In the present experimental study, an alkaline capture and conversion system for high atmospheric CO2 transfer rates and robust biomass productivity was used. To overcome the problem of excessive energy costs and evaporation (owing to the lower availability of CO2 in the air i.e. 400 ppm), growth media with high pH and alkalinity was used. Such a highly alkaline media is able to dissolve a large amount of carbon dioxide as bicarbonate, facilitating the biomass generation by the cyanobacteria. A consortium of cyanobacteria was used, from the microbial mats collected from alkaline soda lakes in British Colombia, Canada. These mats in nature contain abundant cyanobacteria that grow at a pH of 10.1 to 10.3. The alkaliphilic cyanobacterial consortium was able to grow at high pH (up to 11,3) and the biomass was comparable to other reported microalgal biomass cultures. The high pH environment enabled the effective regeneration of the growth medium by direct CO2 capture from air .

In another separate study, it was seen that a cyanobacterial consortium of L. limneticus and L. subtilis was able to sequestrate CO2 using Na2CO3 as an inorganic carbon source. Almost 71% sequestration rate was observed, 15% CO2 being the most optimal concentration .

[1]Ataeian, M., Liu, Y., Canon-Rubio, K. A., Nightingale, M., Strous, M., & Vadlamani, A. (2019). Direct capture and conversion of CO2 from air by growing a cyanobacterial consortium at pH up to 11.2. Biotechnology and bioengineering, 116(7), 1604–1611. https://doi.org/10.1002/bit.26974

[2]Avnish Nitin Mistry, Ganta Upendar, Sunita Singh, Jitamanyu Chakrabarty, Gautam Bandyopadhyay, Kartik Chandra Ghanta & Susmita Dutta (2020) Sequestration of CO2 using microorganisms and evaluation of their potential to synthesize biomolecules, Separation Science and Technology, 55:2, 332-345, DOI: 10.1080/01496395.2019.1577453

Direct Air Capture and Sequestration (DACS)

Subash Chapagain
Subash Chapagain Sep 07, 2020
Though many physicochemical technologies are being tried and tested to sequester the floating carbon (in the form of oxides, mostly carbon-dioxide), Direct Air Capture and Sequestration technology seems like the most efficient and promising one. In DAC, synthetic sorbents are used to capture the atmospheric CO2 directly. This is a chemical process, and the sorbents used are in the form of amines, alkali/alkaline earth metal oxides, polymers, and similar molecules that can interact with the CO2 in the air and capture it. The process directly removes the atmospheric CO2 by using scrubbers and produces concentrated CO2 as the end product, which will be sequestered or used for other purposes in the future. The scrubbing process makes use of either adsorption (surface attachment) or absorption (matrix-entrapment) or both, or specialized membranes. Though this process might seem similar to another sequestration technique called Carbon Capture and Sequestration (CCS), DAC differs from CCS in that the point source of CO2 extraction is atmospheric air rather than concentrated point sources like coal-fired power plants, chemical plants, etc. As of 2020, this technology has been pioneered into a pilot-scale operation by Carbon Engineering, a Canada based environmental technology company. As they claim, the technology is industrially scalable and affordable. On top of that, the technology is deemed to capture CO2 from the air in a closed "chemical loop" that makes it possible for the same capture chemicals to be reused over and over. The closed-loop process is non-volatile, ensuring a minimal amount of wastage. This video shows how the technology works. Read this paper to see the fundamental scientific and engineering details of the technology.

Pulling carbon from the air and injecting it into underground rocks

Darko Savic
Darko Savic Oct 19, 2020
In southwestern Iceland, there are direct air capture machines that pull CO2 directly from the air and inject it into underground stones, where the gas can be stored for millennia.

Climework's Orca will take carbon dioxide removal to the next level: it combines direct air capture technology with the underground storage of carbon dioxide on a large scale. It can capture 4.000.000 kg of carbon dioxide per year. Way to go!

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General comments

Darko Savic
Darko Savica month ago
Here is a recent overview of the topic, explaining 7 carbon sequestration methods https://youtu.be/2J05vC3umE0
Darko Savic
Darko Savic3 months ago
Here's a recent new overview of humanity's drive to reduce carbon dioxide https://youtu.be/DGoOmUIYVSo
Darko Savic
Darko Savic3 months ago
Elon Musk is pledging a 100 million prize for best carbon capture technology https://twitter.com/elonmusk/status/1352392678177034242?s=20
Darko Savic
Darko Savic7 months ago
In this youtube video https://youtu.be/GfRo8_RfefA Joe Scott talks about a few viable options that are being worked on.