Clean Coal?

Coal powered utilities have a “solution” to global warming caused by carbon dioxide, and they call it “Clean Coal” and “Carbon Sequestration.”  To many environmentalists, clean coal is simply an oxymoron.

 Also known by its technical name, Integrated Gasification Combined Cycle or IGCC, this new type of electric generator heats coal in the presence of oxygen, producing carbon dioxide and hydrogen gas, and leaving a bunch of the nasty stuff found in coal (mercury, sulfur, etc.) which would be released into the air in ordinary coal combustion plants stays (mostly) put.  The hydrogen is separated off by absorbing the carbon dioxide with an amine solution (other methods are in the works, but this is the only one in use now), and the hydrogen is burnt in a modified turbine to produce electricity.

Compared to conventional pulverized coal plants, this is an elegant solution.  There is much less of a problem with the traditional pollutants associated with coal (mercury, particulates, etc.), the whole process is slightly more efficient than pulverized coal, producing slightly more electricity per ton of coal burned (and carbon dioxide produced), and there is the theoretical possibility of capturing the carbon dioxide and putting it somewhere where it won’t enter the atmosphere and heat our planet (i.e. “sequester” it.)

On the downside, in the three IGCC plants currently in existence, there has been no attempt to capture CO2, for the simple reason that we don’t have any place good to put it, and any attempt to do so would require a significant portion of the energy output of the plant (I’ve heard numbers ranging from 10% to 30%), meaning that a lot more coal would have to be burnt just to deal with the carbon dioxide emissions.

FutureGen proposed design renderingXcel Energy, is with grants from the federal govenrment and other partners, is planning a 300 to 350 MW IGCC plant in Colorado, which will be the first in  the United States, as well as the first anywhere in the world to attempt carbon sequestration (most likely by taking some of the carbon dioxide and injecting it down old oil wells, a practicepioneered at the Wyburn oil field in Canada.  Some other methods of sequestering carbon dioxide, such as injecting it in brine formations, have shown the potential to form acid, leading to worries that the acid will breach the geologic formation, leading the carbon dioxide to escape.

In addition, according to an interesting article Can Coal be Clean? in the Nov 30 Economist, IGCC plants are also much higher maintenance than the old pulverized coal plants.  So is it any surprise that among the 150 new coal plants now being planned, only one or two are IGCC, and of those, only FutureGen is actually planning to test all the technologies that the utilities are holding up as the “solution” to carbon dioxide emissions, while the rest are just more business as usual.

Should we hold out much hope for IGCC with carbon sequestration?  Maybe in 30 years, after all the kinks have been worked out.  Carbon sequestration today is at a similar level of technological maturity as wind was in 1980.  Now that wind and solar have been generating electricity for 30 years, and are proven to work well, that’s where we should be focusing our efforts. 

I applaud FutureGen as a research project, but if we’re looking for a carbon neutral place to get our electricity today, IGCC with sequestration is a distraction.  However, if it can be made to work, I hope to be around when we have IGCC with carbon sequestration, fuelled by biomass, for a net carbon-negative power source.

Some numbers:

According to this testimony before the US house of Represnetatives, cost of electricity from IGCC without sequestration is $46 to $49 per MWh, and cost to sequester CO2 is estimated at $3-$10 a ton, depending on method an geology.  At treehugger, I found an article which implied that IGCC produces about 1 ton of CO2 per 5 MWh, which would make the cost of sequestration between $.60 and $2.00 per MWh, or .6 to 2 cents per kWh.   We do need to consider the fact that some of that $3-$10 per ton cost comes in the form of cost of electricity, so the calculation of cost of energy becomes depends on the source of electricity for sequestration, and how much of that carbon is sequestered.  None of this includes the cost of carbon capture, which would likely be low if only a fraction of the CO2 were captured, but become more expensive as the 90% or so theoretical limit is approached.  60% capture seems to be a number that the people who study this think would not be onerous in terms of cost.

 There is an incredible pile of information to sort through at

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1 Comment

  1. Thanks for the numbers, Tom.

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