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