So I was doing some digging and found some old notes I had made while reading about Carbon Capture and Storage (CCS) techniques. These are schemes that seek to trap Carbon Dioxide (CO₂) and store it somewhere, usually underground, rather than emit it to the atmosphere. CCS is largely sold as a solution to reduce climate change, but it can also provide a source of CO₂ for end users like oil fields using enhanced oil recovery.

There are literally dozens of different schemes out there, and I wanted to compare the cost of each when it came to reducing carbon dioxide emissions. Trying to do an apples-to-apples comparison of is extremely difficult, but what I did was go through three sources:

•  IPCC, 2006. “Intergovernmental Panel on Climate Change (IPCC) Special Report on Carbon dioxide Capture and Storage Chapter 3: Capture of CO₂” Cambridge University Press, Cambridge, England.
•  EcoBusinessLinks, Feb. 14 2010. “Carbon Emissions Offset Directory – Price study of offsetting emissions of carbon.” http://www.ecobusinesslinks.com/carbon_offset_wind_credits_carbon_reduction.htm
•  MacKay, David. 2009. “Sustainable Energy – without the hot air.” UIT Cambridge Ltd., Cambridge, England. http://www.withouthotair.com/ (Relevant old post here)

…and then I tried to put everything in the form of $US per metric ton of CO2 release avoided. All prices are from 2000-2010, for the U.S. lower 48, and I did not make any adjustments for inflation or location. Prices are averaged over the lifetime of the plant or service, so something with high upfront costs but a long lifetime can have a lower cost than a cheap but short-lived solution. None of the prices include compression and storage, because that price varies very heavily based on how close the storage location is.

Note that the measure I selected, $/ton release avoided, is different than $/ton of CO2 captured. This is because some techniques increase power demands:

For example, suppose a power plant releases 1.0 mt/d CO2. A new CCS process will capture 90% of the carbon dioxide, but increases the energy consumption 50%, so now 1.5 mt/d CO2 is generated but 1.35 mt/d CO2 is captured, leaving 0.15 mt/d release. Therefore 1.0-0.15 = 0.85 mt/d CO2 release is avoided. If the CCS plant costs $10/d more than the original plant (averaged over the life of the plant), then costs will be 10/0.85 = $11.76/mt CO2 avoided.

By contrast, 10/1.35 = $7.41/mt CO2 captured. If there were a commercial market to sell CO2 into, then that cost might also be of interest.

So again, in this article I’m talking about $11.76/ton CO2 price.

Results

Because it’s more efficient to install CCS into new power plants than retrofit existing plants, the costs are different.

Estimated range of cost (2000s $US) per metric ton of CO2 release AVOIDED, by technology category

• New pulverized-coal power plants with CCS $29-51
• Coal plant retrofits $45-73
• New natural gas plant with CCS $37-74
• Integrated gasification combined cycle (IGCC) coal power plants $13-37
• Steam reforming $24-56
• Oxyfuel $78-88.
• CCS to other industries like oil, petrochemical, ethanol fermentation, pulp mills, ranges $10-116…big discrepancies
• Atmospheric CO2 distillation: perhaps $140 after much more R&D? Highly speculative
• Buying carbon offset credits $3-30

Check out how it compares to this graph of the CO2 price required to change behaviors.

 Conclusions

This data is a bit old, but we can draw some general conclusions:

• CCS on new plants is much more economical than for existing plants.
• Coal plants provide more bang-for-your-buck, which makes sense because coal generates more CO2 per unit of energy than natural gas.
• When trying to put CCS into miscellaneous industries other than power, there’s a huge range in the costs. Which makes perfect sense; presumably a huge mega-refinery is a better target than a small paper mill.
• Carbon offsets are cheaper than CCS for almost all scenarios. They are also more reliable, instant, and can be dropped at a whim, so they seem the best option. Which is a problem, because it suggests you’re better off “greenwashing” by buying a few credits and not changing your core business. That’s tempting, but it won’t provide any technological experience in the long run.