Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Oxygen geosequestration – perhaps not such a good idea?

with 2 comments

I was listening to The Atomic Show * a couple of weeks ago, and Rod’s guest – John Wheeler, if I remember correctly – raised an interesting point.

Most of the mass of a carbon dioxide molecule is oxygen – so if we talk about sequestration of carbon dioxide underground, aren’t we removing huge amounts of oxygen from the biosphere?

That might present a bit of a problem. That oxygen is kinda important for a few things which I, for one, really care about.

Let’s see about quantifying it. [In case you had never noticed until now, I like quantifying things. I think it’s pretty important.]

The Earth’s atmosphere has a mass of about 5 * 10^18 kilograms, and is comprised of 21% oxygen.

That’s a total of 1.05 * 10^18 kilograms of oxygen.

Total world emissions of carbon dioxide due to anthropogenic technological activity are about 2.7 * 10^13 kg per year, globally. Of course, that will probably increase in future – how fast it will increase, and how we might slow that down – is a problem that many people throughout the world are busy thinking about and working on at present. But let’s just assume, for my purposes, that it doesn’t increase.

Let’s say, just making up some very rough hypothetical numbers here for arguments sake, that we can capture and store 70% of total anthropogenic technological carbon dioxide emissions worldwide, and that we do that for 80 years.

That’s a total of 1.5 * 10^15 kg of carbon dioxide, which corresponds to [ 32 * (1.5 * 10^15 kg / 44) ] 1.1 * 10^15 kilograms of oxygen.

That’s 0.1% of all the oxygen in Earth’s atmosphere – gone – in just 80 years. That’s probably going to be a problem.

Just another reason why, personally, CCS/geosequestration is a bad idea, and isn’t really a worthwhile solution to anything.

[* Shameless promotion – but hey, I personally think it’s a really good podcast and I recommend listening to it.]

Written by Luke Weston

April 16, 2008 at 9:43 am

2 Responses

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  1. Actually, the oxygen is lost as soon as it is combined with the carbon, so whether it is underground as CO2 or floating in the atmosphere, it is lost for us to use it to make more CO2 (by breathing).

    Bill

    April 16, 2008 at 5:52 pm

  2. But if the carbon dioxide remains in the biosphere then it is available for plants to take up – if there is enough “capacity” of plants on the earth, then the oxygen is released to the atmosphere and the carbon “sequestered” in the carbon cycle.

    Luke Weston

    April 17, 2008 at 1:43 am


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