Energy and Material Balance of CO2 Capture from Ambient Air

[OKIsItJustMe]

http://pubs.acs.org/cgi-bin/sample.cgi/esthag/asap/html/es070874m.html

Energy and Material Balance of CO2 Capture from Ambient Air

Frank Zeman*

Columbia University, Department of Earth and Environmental Engineering, 918 Mudd MC 4711, 500 West 120th Street, New York, New York 10027

Received for review April 13, 2007

Revised manuscript received August 19, 2007

Accepted August 20, 2007

Abstract:

Current Carbon Capture and Storage (CCS) technologies focus on large, stationary sources that produce approximately 50% of global CO₂ emissions. We propose an industrial technology that captures CO₂ directly from ambient air to target the remaining emissions. First, a wet scrubbing technique absorbs CO₂ into a sodium hydroxide solution. The resultant carbonate is transferred from sodium ions to calcium ions via causticization. The captured CO₂ is released from the calcium carbonate through thermal calcination in a modified kiln. The energy consumption is calculated as 350 kJ/mol of CO₂ captured. It is dominated by the thermal energy demand of the kiln and the mechanical power required for air movement. The low concentration of CO₂ in air requires a throughput of 3 million cubic meters of air per ton of CO₂ removed, which could result in significant water losses. Electricity consumption in the process results in CO₂ emissions and the use of coal power would significantly reduce to net amount captured. The thermodynamic efficiency of this process is low but comparable to other "end of pipe" capture technologies. As another carbon mitigation technology, air capture could allow for the continued use of liquid hydrocarbon fuels in the transportation sector.

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...

(Better yet, let's eliminate the "liquid hydrocarbon fuels in the transportation sector" but try extracting CO₂ from the atmosphere...)

[phantom power]

1. 350kJ/mol. Sweet, now I just have to figure out...

how many moles we need to remove. And then I'll have a figure that numerically justifies my constant feelings of dread.

[phantom power]

2. OK, to get us back to 1870 levels of CO2 (290ppmv)...

I get a figure of about 6200 exa-Joules. In other words, about 15 years worth of human civilization's total energy budget.

Oh, and that is of course assuming that we stopped emitting any more. So all we need to do is get ourselves to zero global emissions globally, and also deploy the equivalent of our current energy demand, and dedicate all of that to CO2 scrubbing, for about 15 years.

We are fucking golden.

Oh, wait. :puke:

[OKIsItJustMe]

3. I tend to be suspicious of such devices

However...

We don't need to remove every bit of CO₂ from the atmosphere this minute. Actually that would be a bad idea.

What we need is a way to decrease CO₂ over a period of time.

The easiest thing to do is to decrease the amount of CO₂ we're putting into the atmosphere, well in theory that's the easiest, but we don't seem to be having much luck with that. Do we?

Devices which capture CO₂ seem outlandish to me; and scaling things up seems to be next to impossible, but perhaps they can be a small part of a long-term solution.

[phantom power]

4. I don't think we've even reduced the 3rd-derivative of CO2 emissions.

Much less reduced the 2nd derivative. to say nothing of reducing the 1st derivative.

Actually reducing the atmospheric CO2 is right out.

[eppur_se_muova]

5. How does this compare to liquefaction/distillation of air, which is already done industrially?

from the article:

"As a thermodynamic minimum, the energy cost is -RT ln (P2/P1) where P1 is the partial pressure of the input stream and P2 of the output stream. Given atmospheric CO2 levels of 380 ppm (13) at ambient temperature (300 K) and a 1 bar output stream, we obtain a minimum energy penalty of 19.6 kJ/mol."

Or, for that matter, membrane diffusion processes ?