The question has been asked many times. Let me try to show you why Carbon Capture and Storage (CCS) is of no value as a global thermostat:
The stated purpose of CCS is to reduce the amount of carbon dioxide (CO2) accumulating in the atmosphere and so limit enhanced greenhouse warming. Let’s put in some real numbers to see how that works out.
According to the U.S. EPA, the average emission rates in the United States from coal-fired generation is 2,249 lbs/MWh of carbon dioxide. We convert 2,249 lbs to 1.02 metric tons for the purposes of calculation.
Using 2007 (the last full year available from EIA here), coal-fired generation accounted for 2,016,456,000 of 4,156,745,000 Megawatthours (MWh) U.S. electric power generation (~48.5%). Thus 2,419,747,200mt CO2 emission from U.S. coal-fired generation (rounded up to 2.42 billion mt).
For simple expedience using CDIAC’s FAQ :
“Q. What percentage of the CO2 in the atmosphere has been produced by human beings through the burning of fossil fuels?”
A. “Atmospheric CO2 concentrations rose from 288 ppmv in 1850 to 369.5 ppmv in 2000, for an increase of 81.5 ppmv, or 174 PgC. In other words, about 40% (174/441.5) of the additional carbon has remained in the atmosphere, while the remaining 60% has been transferred to the oceans and terrestrial biosphere.
[Note for those not familiar with the units: PgC are petagrams of carbon, petagrams are one billion metric tons and carbon, with an atomic weight of 12, combined with 2 oxygen, atomic weight 16 (12 + 16 + 16 = 44) is 12/44 of the mass of carbon dioxide. We are only interested in the percentage emission accumulating in the atmosphere here.]
Atmospheric accumulation from U.S. coal-fired generation is then 2.42 (emission) x 0.4 (persistence) = 0.968 billion metric tons carbon dioxide (2007).
Again using CDIAC’s FAQ :
“Q. In terms of mass, how much carbon does 1 part per million by volume of atmospheric CO2 represent?”
A. Using 5.137 x 1018 kg as the mass of the atmosphere (Trenberth, 1981 JGR 86:5238-46), 1 ppmv of CO2 = 2.13 Gt of carbon.”
[note: I believe they are using Gt (gigaton) for 1 billion metric tons here since their calculation begins with mass in kilograms.]
And converting the carbon value to carbon dioxide: 2.13 * 44/12 = 7.81 billion metric tons carbon dioxide = 1 ppmv of the atmosphere.
Total atmospheric persistent carbon dioxide emitted from all U.S. coal-fired generation (in full year 2007) = 0.968 / 7.81 = 0.12 ppmv.
The conclusion then is the total contribution if all U.S. coal-fired generation emissions are captured and stored immediately and permanently is a slowing in atmospheric accumulation rate by 0.12 ppmv/year. Given the number of U.S. coal-fired generation plants not being approved or constructed in the name of constraining carbon emissions I see no reason to increase this value when projecting forward.
How much can this help assuming all claims about enhanced greenhouse warming are true?
Well, assuming we could start that much CCS from the beginning of 2011 and maintain avoidance of 0.12 ppmv/year through 2100 (90 years) that would avoid an exciting 90 * 0.12 = 10.8 ppmv atmospheric carbon dioxide by end of century, wouldn’t it?
Is that a big deal? Will it make an appreciable difference to projected temperatures in 90 years?
Using the IPCC’s simplified expression for calculation of radiative forcing due to CO2 (mirrored here) deltaF = alphaLN(C/Co) and 380 ppmv for our base year 2007 we get a difference of 5.35 * ln(390.8/380) and thus we get a change in forcing of slightly less than 0.15W/m2, which, depending on whose lambda values we use (climate models use λ values of 0.75 ± 0.25 °C per W/m2; Nir Shaviv derives 0.3 K/W/m2 here) we derive 0.045 to 0.15 °C avoided warming over the 90 years to end of century.
Indeed even if we allocate the total guesstimated warming of +0.75 °C since the Industrial Revolution to increased atmospheric carbon dioxide it is still the result of +100 ppmv, so 0.75 * 10.8/100 = 0.081 °C avoided warming from complete coal-fired CCS even if carbon dioxide is in total control of global mean temperature.
To achieve this CCS would require something in the order of 30% more coal consumption to drive the capture, transport and storage, plus we need to amortize the financial impost of retrofitting all coal-fired generation, provision of pipelines or other transportation (railcar tankers or tanker trucks, road/rail transport costs? ), injection costs and monitoring. What should we call it — conservatively 50% consumer cost increase? That would take the U.S. industrial electricity price (2007) from $64.00/MWh to $96.00, something guaranteed to harm industry and employment and to increase consumer costs across the board.
Even if we assume Hansen’s most extreme climate sensitivity estimate of 1 K/W/m2 to be correct we would be consuming 30% more coal and increasing industrial electricity cost by 50% in a effort to “save” at most 0.15 °C avoided warming over the 90 years to end of century.
That “saving” of 0.15 °C over 90 years stems from a magical cessation of all U.S. coal-fired electrical generation carbon dioxide emissions from the end of next year while increasing coal consumption by 30% with its associated collateral environmental damage from mining operations. Can’t consider that environmentally friendly when it increases resource demand by so much and yet yields such imperceptibly small result.
Can’t call it people friendly either, since it significantly increases costs and so reduces U.S. industrial competitiveness, employment opportunity and consumer spending power. Effects which will be compounded by restriction of new coal-fired generation capacity leading to further electrical price increase as less useful and more expensive options are employed to maintain the baseload electricity supply.
The corollary, of course, is that since shutting down all U.S. coal-fired power plant emissions has so little potential effect on global mean temperature over the rest of the century then obviously we have very little to fear from rising levels of CO2 in the first place.
And that’s why we don’t think CCS or any form of carbon constraint has any place among potential mitigation strategies should global mean temperatures rise dangerously for any reason.
There are things we could usefully do to cap global mean temperatures if required but carbon control is not one of them.