61 comments on Q & A With Paul Hanrahan, CEO of AES
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61 comments on Q & A With Paul Hanrahan, CEO of AES
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You probably dont have to sequester the same CO2 as is produced - any plant anywhere in the world that can extract CO2 out of the air and sequester it can offset similar C02 emissions elsewhere. The problem is of course to do it with an energy source that makes the whole operation a net C02 sink.
This is where the intermittent power from wind can perhaps play a role. A napkin-calculation to show net energy from say a coal-fired plant with 50% CO2 sequestration using remotely located wind powered plants would be interesting. In other words - how much energy does it take to sequester the CO2 produced by generating 1Kwh of electricity in a coal-fired plant. Anyone?
Would the EROEI even be > 1? Does it matter if you are trading peak supply energy for base load supply?
Francois
Willi Broecker has recently been promoting a scheme to draw down atmospheric CO2 with huge fans, for sequestration. This strikes me as completely ludicrous compared to tapping the non-dilute stream from a power plant.
Some people will go to any lengths to avoid the feared phrase "Plant a tree!". After all, how ludicrous is that? Green plants that sequester carbon... did anyone ever hear something more nonsensical? Didn't we all learn in school that trees produce more CO2 at night than they assimilate at daytime? Didn't we all hear about tree roots that tunnel down to the geological coal deposits to supply the trees with the ever needed carbon?
:-)
I will give you one that essentially requires no energy. Shell fish farms. Assume 1000 tons of oysters a year and the weight of meat is 20 percent. It works out to about 350 tons of CO2 a year. Yes, trivial I know.
I don't think this would be really trivial if it could be used to offset some of the fishing quotas. We know that we are greatly overfishing almost every single species we use from the oceans. If a greatly expanded shell fish industry could remove some of that stress on our oceans and at the same time act as a carbon sink, it would be a win-win. 1000 tons of oysters are nothing. If we want to feed the world, we will probably need a hundred million tons of shell fish (current fishing quotas are 90 million tons of fish, I believe). That amounts to 35 million tons of CO2. Still small compared to the 7Gtons of carbon we put in the atmosphere but not trivial by any measure. I don't know where the other environmental limits of this industry are, but maybe it can make an impact, after all.
Scrubbing the atmosphere of CO2 rather than individual exhaust streams will not be an efficient solution today unfortunately. The key issue is concentration. Scrubbing processes work more efficiently with higher concentrations to remove.
The atmosphere has ~400ppm CO2
Fossil power stations emit 5-10% CO2 in the stack
The amount of energy required to remove CO2 from air would be huge, with very very low efficiencies in comparison to doing the same on a more concetrated stream.
The power generation efficiency loss from installing CO2 capture / storage on a gas-fired power plant is circa 10-15%. Assume that coal is roughly the same. ie. A CCGT will fall from 55% to 45%, coal from 40% to perhaps 30%. Cost of the equipment for capture and storage is also high, and combined with the energy used to power the capture process could potentially add 50% or more to today's electricity price.
I think a big question here is the general population's willingness to pay for this. Everyone who uses energy will have to pay in the end. Currently there are few other solutions which can be deployed - lets face it man is not going to give up fossil fuel in 10 or 20 years, so CCS will have a vital bridging role to play in managing CO2 before cleaner energy sources start to become dominant.
I'd have to dig through the IPCC report, but my understanding is that full extraction and sequestration costs you something like 25% of energy produced *depending* upon how far you have to pump the CO2 to sequester it.
In practice, from an economy-wide perspective, dealing with the CO2 from coal plants is likely to be about the cheapest form of industrial abatement (although preserving rainforest, collecting methane off garbage dumps and pig farms, etc., will be even cheaper).