Carbon capture and sequestration gets heralded as a great way to lower CO2 emissions and keep burning coal. Unfortuantely, it also kills the efficiency of the coal plant, meaning that every other environmental externality associated with coal-fired generation -- from mountaintop removal to power plant siting -- is exacerbated by CCS. Planet Ark puts it succinctly:
The process called carbon capture and sequestration requires as much as 20 percent of the electricity a power plant generates.
That essentially means that for every five coal plants using the technology, a sixth would be required just to power the capture and burial of carbon dioxide produced.
To unlock wind power, put a price on carbon
Another coal plant bites the dust
Blowing up our clean energy future
Comments
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GRLCowan Posted 10:37 am
07 Jul 2008
A relevant abstract. Elsewhere in that comment string, some discussion of the energy needed to compensate for the legacy CO2 from a joule of coal fire long ago.
"Whack-a-mole" implies falsehood, implies that when a tonnage of CO2 is sequestered -- ideally as mineral dust lying on large fractions of the Earth's surface-- an equal tonnage of additional emission results. Very large nuclear-powered olivine dispersal plants would certainly make this untrue, but even coal-fired olivine broadcasters would make it about 90 percent untrue.
--- G.R.L. Cowan, H2 energy fan 'til ~1996
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Des Emery Posted 2:20 pm
07 Jul 2008
But I wonder what the cost would be in comparison to sequestration if we were to "de-compose" it into its component carbon, as a solid, and oxygen, as a gas?
Des Emery
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GRLCowan Posted 2:42 pm
07 Jul 2008
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Des Emery Posted 3:09 pm
08 Jul 2008
I really have no idea of the comparative cost of capturing CO2 from smokestacks, transporting it to storage sites, and pumping it underground or in devising a system that just destroys it.
Surely if people contemplate electrolysis of H2O to obtain the hydrogen as a fuel, decomposition of CO2 could be considered as a way to eliminate its threat to the atmosphere?
P.S. I am not a troll. At least, not when I last looked in the mirror.
Des Emery
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David Mack Posted 2:31 am
09 Jul 2008
Hydrocarbons typically burn with oxygen (O2) to form carbon dioxide and water, with the water in either vapor or liquid form.
CH4 + 2 O2 --> CO2 + 2 H2O
The energy released are as follows:
889 KJ if the product is liquid water
802 KJ if the product is water vapor
KJ are kilojoules, a unit of energy
The products you get depend on the design of the combustor and whether the heat from the water vapor can be captured. Above, I've described an ideal reaction that assumes complete combustion and no production of carbon monoxide (CO) or other less desirable products.
Your question is how the reaction would change if we got solid carbon as a product. It impossible to get 100% solid carbon in a 1-step process, but let's say we designed a multi step combustion process can achieve the following overall reaction with no other losses.
CH4 + O2 --> C + 2 H2O
The energy produced would be:
496 KJ if the product is liquid water
409 KJ if the product is water vapor
So even if we could design a combustor that could could turn fossil fuels into solid carbon and water without significant losses (highly improbable), we'd only get about 55% to 51% (496 KJ/889 KJ to 802 KJ/409 KJ) of the energy we would get if the products were carbon dioxide and water. The other way to look at this is that there would be at least 45 to 49% losses using this process (probably more).
For carbon sequestration, the article estimates it would take 20% percent of the power of the plant to run the sequestration system, which is a significant improvement over storing the waste as solid carbon.
In any case, if you read more of Sean's posts, he claims that there are many cheaper carbon free sources of energy than techniques using sequestration. In the near term (10 years), I'd definitely agree with him. In the future, it is conceivable that losses due to sequestration (and other issues related to clean coal) are solved and clean coal becomes a cheap somewhat sustainable technology. Presently, I think its a ploy by the coal utilities to get subsidies to invest in something really stupid. The key is to design policies that don't favor any technology, but goals (clean energy). If coal with sequestration is that technology, so be it, but I wouldn't hold my breath.
There are also issues with making sure the CO2 stays below the surface. While it might seem easy, the cost of getting this aspect of the technology wrong is really scary.
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Green Tech Posted 6:01 am
09 Jul 2008
Introducing sulfur clean up on coal power plants also knocked back their efficiency but did that make sulfur clean up a bad technology? True carbon capture and sequestration introduces a big energy efficiency penalty because it's a bigger job and more ambitious. Lots of processes could be more energy efficient if we choose to use the environment as a giant dustbin.
If we go down the road of Carbon capture, where does this leave us? More coal would be used to make more expensive power but there would be lots of it and it would be infinitely cleaner. Great! Bring it on. This will make other technologies more competitive and stimulate development.
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Sean Casten Posted 6:23 am
09 Jul 2008
By contrast, putting scrubbers on stacks adds parasitic loads, driving efficiency down in the name of sulfur reduction. The great tragedy of the Clean Air Act is that it favors the expensive stuff over the cheap stuff, needlessly increasing the price of energy and - perhaps worse - furthering the misbegotten idea that one cannot be both environmentally and economically responsible.
We need to do better on carbon. CCS is simply an old, outdated approach to a problem that we already know how to solve more cost effectively, in the same manner as we did with sulfur. Use lower carbon fuels. Use more efficient combustion devices. And only once those are all satisfied do we need to start doing the really expensive stuff. Not first.
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Jay Alt Posted 1:56 am
10 Jul 2008
So lets use the interest in these projects as a carrot. Our leaders shouldn't fund CCS (or nuclear) projects without them being part of a package with a solid array of renewable energy and conservation policies.
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Green Tech Posted 6:07 pm
11 Jul 2008
Don't confuse lower energy efficiency of capture technology with bad technology. Let me use a simple example, if we all just tossed our trash in the street and left it there we would be more fuel efficient. We would not burn energy in the trucks hauling away the trash. Besides the lower energy efficiencies of capture are, in part, a normal issue of new technology. We have to build these plants and learn about them in order to make them more efficient and cheaper.
It does sound like there are specific issues around the clean air act that could have been handled better. For me the lesson is to make sure new legislation is drafted better not to avoid better technology.
Finally, you have to consider the big picture with oil and gas. There is only so much in the ground and we are slowly but surely using it up. Pretty much all the good easy to extract high quality stuff is gone or going. We are already heavily reliant on oil and gas from the Middle East, Russia and Africa. Coal on the other hand we have lots of and in our own back yard. One of the reasons we don't use more coal, instead of expensive oil and gas, is that it's pretty dirty in comparison. In fact you can argue that fuels like gas are in part more expensive because they are cleaner. It seems to me that if we think we will use more coal in the future we really need to think about cleaner ways to use.
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GRLCowan Posted 10:08 pm
11 Jul 2008
--- G.R.L. Cowan, H2 energy fan 'til ~1996
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Sean Casten Posted 10:43 pm
11 Jul 2008
Let's look at just one of these externalities - the need for new generation. US electricity demand grows fairly steadily at 1 - 2% per year. Which means that all else equal, we need to add about that much generation capacity per year to keep up with demand.
So now let's say we outfitted all of our coal fleet with CCS. That's 50% of our generation base, and a 20% parasitic load. Which means that in one fell swoop, that would cause us to increase the total generation base in the US by 10%! When you consider that generation reserve margins are falling as it is, we can barely keep up with the current rate of load growth - and this would increase it by a factor of 5 - 10x, at least in the short term.
Now of course there are things we could do with conservation or other measures to lower that 1 - 2% number. But CCS is going dramatically in the other direction. And that's simply one of the moles that pops up once you whack the CCS one.
Bottom line is let's not assume that whacking away at this particular mole is in the national interest. We would be better served to change the rules of the game, and pursue solutions - from efficiency, to renewables to regulatory reform - that don't force us to pick between competing moles.
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GRLCowan Posted 3:03 am
12 Jul 2008
CC from the atmosphere is not outfitted to any particular emitter, rather, to all the world's emitters.
... let's not assume that whacking away at this particular mole is in the national interest. We would be better served to change the rules of the game, and pursue solutions - from efficiency, to renewables to regulatory reform ...
... so that fossil fuel interests can't continue to block nuclear. But none of that takes down the several-hundred-gigatonne slug of CO2 that has already been put up.
--- G.R.L. Cowan, H2 energy fan 'til ~1996
http://www.eagle.ca/~gcowan/boron_blast.html
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Sean Casten Posted 5:17 am
12 Jul 2008
In other words... if it's such a good idea, what's keeping people from doing it?
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GRLCowan Posted 3:44 am
13 Jul 2008
Here, R.D. Schuiling projects costs of $35-55 per tonne C, and says "A large field test with olivine has started this week [of May 18, 2008] in the Netherlands".
I accept the fact that CO2 can be absorbed into rocks, at least on geologic time scales. But if this is going to be done as a near term fix on the environment, I'd sure like to see someone putting projects in, and proving that there is an economic case to be made.
In other words... if it's such a good idea, what's keeping people from doing it?
It's garbage collection, a thing that long has been known not to happen without public funding. Government is taking the money it would cost from fossil fuel consumers, but spending it otherwise.
At least one recent article that appeared in a British web journal called "The Engineer" discussed CCS without acknowledging that it could be done centrally. I think there have been several others. Also there was Zarembo in the L.A. Times acknowledging the lame Klaus Lackner version and ignoring the non-lame R.D. Schuiling one.
Authoritative sources that knock over legions of straw men and don't acknowledge that a real one, to which their arguments don't apply, exists seem to be effective in persuading people that it must not. To me the question isn't, why do I bang on about this, rather, why don't more people do so.
--- G.R.L. Cowan, H2 energy fan 'til ~1996
http://www.eagle.ca/~gcowan/boron_blast.html
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Max8806 Posted 4:23 am
13 Jul 2008
Regardless of whether GRL's preference pans out, this point definitely holds for other tricky-to-measure offsets being tossed around, like the land-use and forestry ones. If you did some of these things from the public purse without incorporating them into the system, you get the climate benefit, without wasting money on measurement, and without creating a really counterproductive incentive to do things worse so you can sell the improvement, which has been the really unfortunate CDM experience. People want to keep around offsets as to keep down the price of permits. You could keep down the price of permits if you gave companies permits for buying me lunch too. The issue is does the method represent a cost effective way of producing actual reductions.
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MAD MAC Posted 4:54 am
13 Jul 2008
Victory in Pattani
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Sean Casten Posted 5:48 am
13 Jul 2008
Indeed, a big part of why I rail so much about CCS is that of all the ways to lower GHG emissions in the atmosphere, it's simply one of the most expensive. Which means that in a market that allows us to be surprised, it's the option which will never get done. Too many in government instead look at an expensive, impractical idea and conclude that it looks like it is an idea worthy of government support to drive the cost down. And since it gets attention well beyond it's likely impact, it ends up horribly corrupting the DC conversation, to an extent that many have equated GHG control with CCS, and therefore concluded that GHG control is stupidly expensive. The logic doesn't hold up, but the conventional wisdom remains.
And yes, some things that are prohibitively expensive do benefit from gov't R&D. But some things that are prohibitively expensive are just dumb ideas. When there are so many more cost effective ways to lower GHGs, CCS would appear to fall into the latter camp (e.g., it's not like we can't lower GHG emissions without it.)
I like to think of CCS somewhat - OK, a lot - perjoratively as directly analagous to human-goat sex. Pay a person a big enough sum of money, and they might deign to have sex with a goat. But there is no reason for government policy to support human-goat sex, R&D to lower the cost of human-goat sex, nor rate-payer funded human-goat sex mandates. (Indeed, even the nominal benefits from such coupling in the form of population control can be more cost-effectively met through other means.)
I smell an absurdist novel on US GHG policy in the making...
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Max8806 Posted 11:25 am
13 Jul 2008
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Des Emery Posted 3:30 pm
13 Jul 2008
Another alternative, but also an expensive one, could be to make our primary energy source Co2-free. That is, nuclear, providing heat to make steam to drive turbines to generate electricity.
Perhaps we need to look for the best solution to the problem rather than the least expensive. Otherwise we might end up paying much, much more than mere money.
Des Emery
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Black Wallaby Posted 7:09 pm
13 Jul 2008
I agree with you on some things you say. (I think)
Let's preserve our natural hydrocarbon resources as a matter of extreme prority for many generations of our offspring to come!
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David Mack Posted 11:58 pm
13 Jul 2008
http://gristmill.grist.org/story/2008/4/1/202110/5791
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