Copyright © 2017 jsd

Some Carbon Sequestration Proposals
John Denker

1  Introduction

Most of the schemes I’ve seen for “carbon sequestration” make no sense whatsoever. The ones that simply store CO2 as such seem unsafe and/or unaffordable, and most of the ones that claim to bind the CO2 chemically would violate the first and/or second law of thermodynamics. However, there is one proposal nthat might be in the right ballpark, maybe.

Short version: Silicate rock reacts with CO2 to form carbonate rock plus silica.

R.D. Schuiling and O. Tickell,
“Olivine against climate change and ocean acidification”


R.D. Schuiling and P.L. de Boer
“Fast weathering of olivine in shallow seas for cost-effective CO2 capture and mitigation of global warming and ocean acidification”

The general idea has been known for a long time:

Berner, Lasaga, and Garrels
“The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years”

I haven’t looked into it super-closely, but I suspect that Schuiling et al. might be underestimating the cost. Still, though, even if the cost is 2x higher than estimated, it’s still cheap compared to the end of the world.

In particular, they make the point that CO2 capture does not need to be done right at the smokestack. One CO2 molecule looks a lot like another, and the atmosphere is well mixed. So CO2 molecules are fungible. You can capture them wherever it’s most convenient. Also you don’t need to take it out overnight. A time scale of a few years is just fine, especially compared to natural processes, which require hundreds or thousands of years to remove CO2 from the atmosphere.

If this is anywhere close to right, it solves important political problems as well as operational problems. Climate deniers rely on saying either there’s no problem, or there’s nothing we can do about it (or both). It dramatically changes the discussion if there is something that can be done at a not-completely-crazy cost.

So we make a rule that says if you want to put X amount of fossil carbon into the air, you have to find enough olivine or wollastonite or whatever to compensate for at least twice that much, grind it to dust and disperse it somewhere. If this has beneficial side-effects (e.g. fertilizer), then so much the better.

I worry that the deleterious side-effects have not been fully accounted for. Olivine can turn into things like chrysotile, which is another name for asbestos, which you might not want to be dispersing in enormous quantities. You want it to end up as carbonate minerals, not asbestos.

If it works out, this is a nice free-enterprise free-market solution. Note that the definition of “free enterprise” does not mean I am free to dump my sewage into your yard. The same goes for CO2. Right now the cost of dumping CO2 is an externality; we need to make the polluters internalize this cost. If you want to burn fossil carbon, the price ought to reflect the real total cost.

David Coady, Ian Parry, Louis Sears, and Baoping Shang,
“How Large Are Global Fossil Fuel Subsidies?”

The neutralization requirement would add a noticeable (but not catastrophic) amount to the price of burning fossil carbon. This makes people unhappy, but still it’s better than the end of the world. The new price, based on the newly-internalized costs, has a nifty free-market side effect, namely making renewables more competitive.

Copyright © 2017 jsd