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Another CO2 Sequestration Proposal

March 7, 2017

Over the past few months there has been a steady stream of announcements intended to show that CO2 could be sequestered, thereby eliminating the threat of climate change from using fossil fuels.

Clexit For a Brighter Future addressed announcements that had been made prior to its publication, but a new method for using CO2 in enhanced oil recovery (EOR) was announced after the publication of Clexit, and this article addresses this latest effort to claim that CO2 can be sequestered.

Net Power LLC announced an “energy revolution” and its Allam cycle, that, “creates low-cost, clean energy.”

However, as explained below, the announcement overstates the potential for sequestering CO2.

Briefly, the Allam cycle burns natural gas and pure oxygen in a gas turbine, and then uses the CO2 that’s produced in the combustion reaction as the working fluid, under high temperatures and pressure, to drive the turbine, with spent, excess liquid CO2 diverted from the system and used for EOR to sequester CO2.

Diagram from Net Power LLC Website

Diagram from Net Power LLC Website

If successful, the Allam cycle would produce low cost CO2 for use in EOR, and eliminate NOx emissions due to not using air, which is mostly nitrogen, in the combustion cycle.

It would not, however, result in resolving the problem of sequestering CO2 in underground geologic formations, primarily because the amount that can be sequestered using EOR is a tiny portion of the total CO2 produced by coal-fired and traditional natural gas power plants.

Currently, as explained in Clexit, the cost of adding equipment to existing coal-fired and natural gas power plants to capture CO2 is prohibitively expensive.

While the Allam cycle produces CO2, in effect capturing it, nearly all existing power plants would have to be replaced with Allam cycle units to eliminate CO2 emissions form power generation.

As established in Clexit:

  • It would require around 440,000 MW of new Allam units to replace the current installed capacity of coal-fired and NG power plants that must be closed to cut CO2 emissions 80% in the US.
  • If each Allam unit is rated 300 MW, it will require building around 1,500 units to replace the existing power plants that must be shutdown. Total cost is at least $480 billion, not counting the cost of pipelines.
  • It doesn’t eliminate CO2 from gasoline usage, which would require building additional power plants if electric vehicles are used to replace gasoline-powered cars.

While the problem of capturing CO2 can be accomplished at very high cost with Allam units, perhaps better than with established CO2 capture methods, the CO2 not used for EOR must still be sequestered in underground geologic formations which, as explained in Clexit, cannot be done with any assurance the CO2 won’t leak into the atmosphere, thereby negating the purpose of sequestration.

A 2012 study by L. Stephen Melzer, Carbon Dioxide Enhanced Oil Recovery (CO2 EOR), established that approximately 3% of total CO2 emissions from power plants is being used for EOR. According to a NETL.DOE, 2012 report, usage of CO2 in EOR amounted to 1.45% of total CO2 emissions from power plants, with the potential for an additional 0.5% CO2 usage.

Given that the Allam method results in a potentially lower cost for CO2, and that most EOR is currently restricted to the Permian basin, there is a possibility that the amount of CO2 used for EOR could increase.

Even if CO2 usage doubled, EOR would only use 6% of all CO2 emissions from power plants, so that 94% would still have to be sequestered in underground geologic formations with no assurance it would remain sequestered for thousands of years.

As in all other cases described in Clexit, the hype surrounding the announcement by Net Power LLC about the Allam cycle, grossly overstates the potential for achieving CO2 sequestration.

In summary:

The Allam cycle, assuming it works as proposed, has the benefit of producing low cost CO2 for EOR, and for generating electricity at low cost without NOx emissions.

The Allam cycle does not resolve:

  1. The high cost of carbon capture, or
  2. Permanently sequestering millions of tons of CO2 in underground formations every year, with any assurance the CO2 will not leak into the atmosphere.

* * * * * *

Clexit For a Brighter Future establishes why the United States should withdraw from the UNFCCC treaty, a treaty most Americans don’t know was ratified by the Senate.

Link to Amazon

This article should be considered a part of this book.

A coupon in Clexit allows the purchaser to also buy Nothing to Fear for $8.00. Clip the coupon and follow the mailing instructions to take advantage of this offer.

Clexit cover

Clexit cover

* * * * * *


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13 Comments leave one →
  1. March 7, 2017 10:18 am

    Just as a matter of curiosity is the cost of producing pure oxygen included in the cost of co2 capture?
    Then in general, Do these people any connection with reality or are they trying to destroy civilisation? I know which one I’d bet on.
    Thanks for the info Donn.
    Steve Guess

    • March 7, 2017 10:29 am

      The cost issue needs to be clarified. Their announcement said the cost of electricity would be comparable to the cost of electricity from traditional natural gas combined cycle power plants, but it’s not clear whether this cost included the facility for distilling Oxygen from the air.

      • March 7, 2017 1:54 pm

        That cost has got to be fairly substantial at the volume required for a power plant. And is probably hidden like the associated costs with wind power.

  2. mjangwin permalink
    March 7, 2017 11:09 am

    I am always suspicious of sequestering carbon dioxide. There’s a lake in Africa that naturally sequesters it (along with other gases). The lake also is subject to sudden release of gases, causing many deaths. Nowadays, they have vents in the bottom of the lake to allow CO2 to move into the atmosphere gradually. They are trying to avoid having CO2 build up to levels where its release is dangerous.

    • March 7, 2017 3:11 pm

      Yes, true. Pipeline leaks could pose a threat, since CO2 is heavier than air and can pool in depressions.

  3. Paul Redfer permalink
    March 23, 2017 12:19 am

    I just heard from a retired scientist at Argonne that CO2 could be stored where shale gas was. How much do you think think this will cost?

    • March 24, 2017 3:35 pm

      I have no idea. However, I doubt CO2 can be sequestered for thousands of years in fracked shale formations.
      Please send me the information so I can look at it.


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