The Why and How of Carbon Capture and Sequestration

Carbon capture and sequestration (CCS) is becoming newsworthy again as the EPA’s clean power proposal is being contested in the court system.

The Wall Street Journal ran an article this week on CCS, but covered less than half the story. This is typical of the media, but the Wall Street Journal should know better.

CCS is seen as a way to cut CO2 emissions 80% to prevent a climate catastrophe.

Two steps are involved in the CCS process. The first step was not covered by the Wall Street Journal.

  1. CO2 from the burning of coal or natural gas is captured during the burning process or from the waste stream after burning has taken place. Alternatively, it is heated to form a synthetic gas from which the CO2 can be extracted.
  2. Captured CO2 is then compressed into a liquid, transported by pipeline to a geologic formation where the liquid CO2 can be injected into the ground and to the geologic formation where the CO2 can be entrapped.

Capturing CO2

Experiments have been conducted for capturing CO2 before, during and after combustion.

Integrated gasification combined cycle (IGCC) power plants cook the coal to form a synthetic gas from which the CO2 can be extracted, allowing the remaining gases, mostly hydrogen, to be burned in a gas turbine to generate electricity.

The coal industry has touted this process as clean coal. Unfortunately, after three such units have been built in the United States, their cost has been shown to be exorbitant at over $6,000 per KW, or about what it costs to build a new nuclear power plant.

Experiments have been done for capturing CO2 while coal is burned in a coal-fired power plant.

Experiments have also been done to capture CO2 from the waste stream of both coal-fired and natural gas power plants.

These experiments have demonstrated that coal-fired power plants must be derated by approximately 30% due to the parasitic loads required for capturing and liquefying the CO2. This means a coal-fired power plant with a rating of 300 MW is converted into a power plant rated 210 MW. In other words, 30% of the electricity generated by the coal-fired power plant is used to capture and compress the CO2.

Natural gas power plants will need to be derated by more than 30% because the waste steam includes less CO2, making it more difficult to capture CO2.

The end result is that a new power plant needs to be built every time three power plants are equipped to capture CO2, to replace the electricity lost from capturing CO2.

One can conclude that it’s possible to capture CO2 from coal-fired and natural gas power plants, but that the cost will be very high.

Sequestration

The captured CO2 must be disposed of underground. This involves transporting the liquid CO2 under high pressures, approximately 2.000 psi, to where it can be disposed of underground. This also was not covered by the Wall Street Journal article.

Transporting CO2 will involve building a series of 24 inch, or larger, pipelines across the United States to transport the liquid CO2 from approximately 400 coal-fired power plants. Additional pipelines would be required for natural gas power plants. The Pacific National Laboratory published a paper concluding that between 11,000 and 23,000 miles of new pipelines would have to be built.

These maps show where pipelines might be located in the United States and Europe.

USA CO2 Pipelines
USA CO2 Pipelines

 

EU CO2 Pipelines 2050
EU CO2 Pipelines 2050

Once transported to where it might be sequestered, the CO2 must be injected under ground into an appropriate geologic formation.

Carbon Sequestration Atlas of the United States and Canada
Carbon Sequestration Atlas of the United States and Canada

An atlas has been compiled of potential sites for sequestering CO2. While there are a few examples of where CO2 has been sequestered, e.g., the Sleipner gas field in Norway, Salah in Algeria and in Alberta Canada, none have involved the quantities of CO2 that would have to be sequestered if there was a serious effort to use CCS.

Currently, the largest underground sequestration operation is the Sleipner gas field where one million metric tons of CO2 are injected annually into the saline aquifer under the North Sea.

This compares with 1,800,000,000 metric tons, or 1,800 times the amount sequestered in the Sleipner gas field. This is the amount of CO2 that would have to be sequestered every year if 80% of the CO2 from U.S. power plants were to be captured and sequestered.

Not only is the quantity staggering, but there is no certainty that the CO2 would remain underground for the thousands of years needed to prevent a climate catastrophe, if the CO2 hypothesis is correct.

Other unresolved issues include:

  • Ownership of geologic formations
  • Legal liability if CO2 escapes or causes harm
  • Whether injecting liquid CO2 underground would cause earthquakes

The massive costs associated with CCS, and the uncertainty that the CO2 would remain sequestered underground for centuries leads to the conclusion that CCS is unrealistic.

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