Sequestration, like so many other “solutions,” no silver bullet

Following my post, Carbon Sequestration; what no-one tells you, I received a couple comments from a reader, pointing out the potential of chemical sequestration, commonly referred to as enhanced weathering.

Of course, none of this was provided with case studies or research into it’s viability and the individual quickly left the conversation, having made their point.

But it’s worth reviewing, because I’m becoming increasingly aware of two camps, both very distinct, but sharing an absolutism approach to their favoured climate change mitigation strategy; the pro-nukes and the sequestration mob. Both are sure that their answer is the one and only true reply, but neither stack up.

I won’t bother here with the pro-nukes, because I’ve discussed them various times in the past.

Yes, biological sequestration is only one possibility. Even the modest targets set by the current Australian government within “direct action” represent massive effort, as my analysis showed. However, there is another, apparently low energy, form of sequestration which relies on rock chemically reacting with atmospheric CO2 to capture it.

This is know as “enhanced weathering” as it is a natural process in itself and what the fans of this want to do is speed it up. It’s euphemism for enhanced erosion. I’ll get to the numbers in just a moment, but we’re talking about billions of tonnes of material needed, to match the CO2. Who honestly believes that mining to this degree is viable, let alone desirable when we factor in the necessary impact to landscapes and aquatic environments both through the direct mining activities and resulting compounds as residue from this process, which will hit environments (unless we go to even greater effort and expense to again bury it) in far great amounts than the background levels?

As for numbers, looking at the Azimuth Project, two minerals that could be used for this process are Olivine and Serpentine.

The ratios for these;

Olivine  Olivine (forsterite) Serpentine Serpentine
CO2 Fe2SiO4 Mg2SiO4 Fe3Si2O5(OH)4 Mg3Si2O5(OH)4
Molar Mass (g/mol) 44.01 203.77 140.69 371.73 277.11
Weight ratio to CO2 1 4.63 3.2 8.45 6.3
Molecules requires for every CO2 - 0.25 to 1 0.25 to 1 0.25 0.25
1 unit weight of CO2 requires how many units?  - 1.6 to 4.63 0.8 to 3.2 2.11 1.57

Annual emissions of CO2 reached 34.5 billion tonnes in 2012. Therefore, for Olivine or Serpentine to capture all of this, we would need between 27.6 and 159.74 billion tonnes of these rocks annually.

From the Azimuth Project page;

Supposedly all the CO2 that is produced by burning 1 liter of oil can be sequestered by less than 1 liter of olivine. The market value of olivine is US $50 to US $100 per ton depending on quality. Plugging in the larger number then 5 trillion dollars a year of this material would absorb all the CO2 currently produced. But of course this calculation is oversimplified, since the spike in demand would send the price much higher.

None of this begins to address the billions of tonnes of residue materials as well.

Some might say that I’m being unfair – most targets aim at around 5% below, say 2000 or 1990 levels. To be generous, let’s say the emissions value was 25 billion tonnes, meaning that we want to reach emissions targets below 23.75 billion tonnes. This means that we want to capture 10.75 billion tonnes of CO2 based on 2012 levels.

This amounts to between 8.6 and 49.77 billion tonnes of Olivine and Serpentine annually for enhanced weathering. This is still a massive industry devoted entirely to scrubbing the atmosphere of our CO2 emissions.

The Australian Prime Minister, Tony Abbott, may call emissions trading a “so-called market in the non-delivery of an invisible substance to no one,” but how can sequestration be anything but a non-delivery market, as much a sink of money as it is carbon?

It doesn’t matter whether you rely on trees, soil, weathering or any other mechanism, sequestration is not the cheap and easy solution that it has been sold as. In every case you are also left with a bank that is useless unless it keeps carbon locked and what then of this material?

There is no such thing as a silver bullet. Reducing our emissions will require a lot of effort, behavioural change and a diversity of solutions, each contributing their own small part. Thus far, very little of this is being addressed or adopted above the barest effort.

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11 responses to “Sequestration, like so many other “solutions,” no silver bullet

  1. I’m the individual who left the conversation. I’m glad it has progressed in my absence.

    The pro-nuclear and pro-sequestration camps are not entirely distinct and absolutist: I’m in both, thinking that each is a big cartridge of silver buckshot.

    But I think the subsidy government gets from fossil fuel users and producers is such that it will footdrag on nuclearization until the buildup of CO2 in the atmosphere is much more serious than it is now, and will then urgently want something to reverse this buildup, i.e. to remove CO2 much faster than fossil fuel-burning will at that time be producing it.

    One case study has been done inadvertently: http://adsabs.harvard.edu/abs/2005AGUFM.B33A1014W

    If you haven’t yet run into R.D. Schuiling, he and the fiendishly antinuclear O. Tickell present the case here.

    • Don’t get me wrong, nuclear power and sequestration have value as part of the mix, but neither are a game changer. We will not sequester the amount of carbon required and keep it locked and nuclear has more problems than merits – the biggest being the behaviour that many advocates have is akin to that historically tied with fossil fuel.

      Here however, like the point made with the Direct Action analysis, is to point out the massive scale required for sequestration which no strong advocate seems to acknowledge.

    • Sorry, re-reading your comment, you misunderstood me. By absolutist I mean that they think the one favoured option is the only mechanism required to achieve the desired results. By distinct, such advocates most often define themselves as such – just look at the blog “Brave new climate” for instance.

      Not everyone who agrees with both to some degree fits the description (your initial comments sounded a lot like that, when now you acknowledge a mix of solutions).

    • Just had a read of the paper you finally offered. It offers little on what I write above, except to say that there’s an industry with a waste product that could be used for sequestration.

      They say that it could amount to as much as 100 million tonnes of carbon a year, or roughly 366 million tonnes of CO2.

      As I say in the post, we have annual emissions of CO2 around 34 billion tonnes, close to 100x the amount this waste product can take up. If we only want the modest target, it’s still around 10 billion tonnes, or 30x the process discussed in your paper.

      And still this waste material requires management that is not discussed.

  2. On the other hand, if you produce a salable product from the manufactured carbonates, some of the costs can be absorbed. Sufficient aggregate is used worldwide that, were all aggregate currently used to be replaced with manufactured carbonates derived from sequestration, 40% of the CO2 could be so sequestered. Obviously, it’s not as simple as that but neither is it as obviously useless as you imply.

    • Wood products (which I know you’re not talking about) are next to useless because they will degrade.

      Would there be an annual market for 10 billion tonnes of carbonates that would keep this CO2 locked?

      This is the point I was really making in the post; there are so many wonderful ideas, but very few that go all the way through the production process. Advocates sell it like a used car with a lick of paint and a motor held together by tape.

  3. Yes, aggregates are used extensively, and the magnesium and calcium carbonates that would be the end result of the serpentine/olivine cycle could be used in that way. Aggregates are used for road and runway bases, in concrete, asphalt paving, and in other applications. Annual worldwide use of construction aggregates is on the order of 26 gigatonnes.

    Currently, such aggregates are mined (quarried) and, to the extent that produced carbonate aggregates were to be used, such mining would be avoided as well. I live in Southern California and, taking the 605 freeway up to the 210 freeway, I see many such quarries.

    I have no particular financial interest in such a process, though my firm (a consulting, testing, and inspection firm in the built environment) deals extensively with aggregates.

    • Initially, that sounds great and would meet out needs to mitigate climate change. But how reliable would the material be compared to the material already used? Is there additional expense in mining this alternative, processing it (ie capturing carbon) and then delivering it as an alternative?

      Looking through the chemical reactions that occur, you also need a lot of water (if you want to be efficient) and you also end up with other output compounds…

      It sounds good on paper, but I suspect it will be costly and produce a lot of waste (hence why we’re not rushing to “save the planet” with scrubbers).

  4. I’m in the middle of a deep (well, deep within my own technical competence anyway) of the energetic and economic viability on my own blog. A commenter upthread (grlcowan) is pushing me there to get it done! He/she is also an active participant at Planet3.0 by the way, which is the site that referred me here (through their Twitter feed).

    In any event, I’d be happy to report back when my analytics are finished. There are certainly issues with the thermodynamics, and people with deeper knowledge of chemical thermodynamics than I have are working on it.

    I don’t suggest that mineral sequestration is THE answer, I don’t think anything holds that status. But I think it there’s a reasonable likelihood that it can be a one of the significant arrows in the quiver.

    • I’m not ruling it out, but it is often seen as an easy solution (especially tree / soil sequestration) which it is not. Nothing is.

      What sparked it up for me was the talk about soil sequestration here in Aust and then enhanced weathering that grlcowan mentioned.

      I believe that it is useful and what you’ve pointed out is the most important part of any mitigation strategy that could possibly have impact; behavioural change.

      You’re talking about making a new market out of a problem, which is the right way to think.

      The scale is the hard part here, based on the questions I raised above. For it to be viable, it needs to be a cheap product (which creates limitations to your process) and you need to reduce waste (not only phyical waste, but resources like water and energy used).

      Feel free to post anything here. I’m certain your thoughts and efforts would be of value to my readers and myself (and I want to avoid an echo-chamber as much as possible).

  5. FYI, there’s a good paper on the processes here.

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