Monday, March 17, 2008

Hopefully Clearing Up Some Misconceptions about CO2 Capture & Sequestration

I wrote the post below last week as a comment on "Clinton on Carbon Sequestration," and since it ended up being rather extensive, I decided to repeat it as its own post. If Sgt. Pepper's misconceptions regarding CO2 capture and sequestration are common, then I hope my comments are informative.

The third paragraph of this post that describes issues with carbon sequestration does not appear to be fully informed about the technology, and may be very misleading as written. First off, carbon sequestration is the act of permanent CO2 storage, separate from the capture of CO2 at an emissions source and its transport to a storage site. Sequestration is NOT an energy intensive process. Most of the energy used in a CO2 capture and sequestration (CCS) system is from the energy required to capture and compress the gas, which typically takes place at the emissions source. CO2 capture technology is primarily intended for power plants (most likely coal facilities), though there are some niche industrial applications such as cement and steel production. No one is proposing to capture CO2 at a mine mouth.

Referring back to the distinction between capture and sequestration, sequestration can hardly be considered in the “theoretical stage.” Injecting and storage CO2 underground has direct analogues in the oil and natural gas industries, and we already inject CO2 underground in Texas for enhanced oil recovery. Several pilot scale CO2 sequestration projects have been completed or are underway in Norway, Canada, and Texas (courtesy of UT’s Bureau of Economic Geology). The word “theoretical” implies a technology has, at best, reached the laboratory experimental stage. Several components of CO2 sequestration technology can be considered commercial, and others have reached pilot scale and are now being developed for commercial scale.

The remaining technological issues with sequestration mostly concern monitoring the gas over long time periods once it’s underground. No one wants CO2 to leak back into the atmosphere or into drinking water aquifers and such, and these challenges are unique to CO2 sequestration. Creating effective regulations for CO2 storage is as big of a barrier to the technology as any remaining technical issues, which is why Clinton praised the WY legislature for its leadership in this regard.

Certain capture technologies can be considered theoretical, or lab/bench scale, but others have reached pilot scale, are being planned for large scale demonstration, and have commercially proven analogies. Chemical absorption of CO2 has been performed in the natural gas processing and ammonia production industries for decades, and UT is among several institutions working hard to scale up this technology for use at coal power plants.

What Clinton is referring to regarding Wyoming is that the state should have a demonstration scale (over a million tons of CO2 per year) storage site there, presumably receiving CO2 from one of the state’s 7 large coal fired power plants (over 100MW) and sequestering the gas in one of its previously identified geologic storage sites. Storing CO2 near the emissions source makes obvious sense to cut down on transport costs, which are mostly capital costs (steel for pipelines,etc.)

And finally, everyone in this class should be well aware that CO2 capture and sequestration will not be “our answer” to global warming, because no single technology will be the answer. It will take several approaches to mitigate the effects of climate change, and CCS will be a vital piece of the puzzle if we continue to use coal for electricity.

I hope these comments clear up some misconceptions about CCS technology. I’d be happy to provide more references, but NETL and the Technical Summary IPCC Special Report on CCS are great places to start.

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