The Dyson Solution and the Soil

A significant fraction of the extra carbon in the atmosphere and ocean is attributed to “land use changes” which in fact basically means  soil loss and forest loss due to agriculture.

Amid his misconceptions about climate science, Freeman Dyson’s most cogent point has always been that we can in principle sequester carbon using biological processes. The details are dubious, but the basic idea still holds some appeal.

Scientific American reports on a small project deployed to do a version of this which failed when cap-and-trade failed in the US and the Chicago Carbon Exchange failed along with it. But the idea of the soil as an essentially infinitely expandible carbon reservoir is something I’d like to see properly refuted, or else more seriously pursued.

I am finding it difficult to find quantitative information on this.

I expect that in the short run soil sequestration mediated by biological processes cannot keep up with fossil fuel burning in terms of rate.

But how long would it take to catch up? Can the process be accelerated? Given extra carbon can extra minerals and appropriate biota be combined with it to deepen the soil layer?  How deep can the soil get? Is there a maximum?

 

Comments:

  1. The last paper I have by Rattan Lal (2010) estimates "the terrestrial biosphere can act as a sink for up to 3.8 Pg per year (i.e., 3.8 Gt); within the US, 0.288, for a cumulative 50 ppm for 100 to 150 years. I haven't read the entire paper in awhile but if I recall, that would bring the soils to saturation. (the paper was in Bioscience 60:9)

    IMO, the reason to do it would not be as a substitute for emissions reductions, but to remove C from the atmosphere that is already there - among others. Co-benefits: soil with more carbon in it holds its moisture better - reducing water use, and increases productivity, and therefore food security. Those working in conservation, including myself, look at it as a way to fund ecological restoration. But implementation is not an easy matter. Part of the reason CCX folded was a very low price for credits - the credits were given for adoption of practices rather than measured and verified carbon storage, which is expensive to do. There is a lot of effort being put in to trying to develop more cost effective ways to do this. But whether even higher credit prices could compete with rising commodity prices is another matter.

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  3. So measuring/verifying soil carbon is impractical? I'd like to know more about this.

    Actually I'm no longer that much interested, since I now tend towards Hansen's carbon tax. Verifying soil carbon would be crucial for cap and trade.

    Methinks recarbonization of the biosphere is necessary for decent survival, but not sufficient without fossil C emissions stop. It's the only game in biogeophysics town. But it is difficult to price. Actually methinks such an endeavor would be economist folly: Soil recarbonization has many beneficial side effects (incl. food security), can be done stone age tech, and is many intertwined processes (add wood energy and char composting). Some money would be welcome, of course, but the thing needs to be culturally or socio-logically appreciated.

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  5. Yes indeed, Lal keeps coming up in my searches on this topic. I should look him up.

    As far as I am concerned the right price for carbon is "high enough"; nothing less will do. I think that is obvious, but I am not sure how to make the case so that the people who are in the carbon pricing business will change gears in that way. Many of the people who like to price carbon would find my approach disempowering.

    My novel question, to my knowledge, is the potential size of the biotic reservoir. Can we have MORE soil than nature intended, rather than less?

  6. (I need to look up again that) half of soil carbon is in Arctic tundra. Add 5% to the other soil C, and you get quite a number. (From my terra preta gardening experiments, 50% C from char is doable. I have a chestnut bonsai in 90% vol char. The only problem that arises is the high water retention capacity: Some of my Malva Alcea drowned in the pot or got root rot.)

    I'm dreaming of carbonizing Swiss mountain slopes and deglaciated areas with char compost. Also the Sahara Great Green Wall would benefit from lots of char. The philanhtropist would start in Haiti with a plant nursery base in the Dominican Republic. But this all needs a radical change away from 20th century agriculture business model. (A business idea I need to start is the carbon negative garden cemetery, since I don't want to end as grotesque and counterproductive as most others. Forget rebirth, do full recycling...)

    Recent book edited by Lal et al: Recarbonization of the Biosphere
    http://www.springer.com/life+sciences/ecology/book/978-94-007-4158-4
    Obscenely expensive. Alas I'm currently making enough money for that luxury, thus have no time/brain left to really read it...

  7. Michael - your novel question is one I have pondered quietly, but although we are nowhere near them, there do seem to be limits on the sink capacity. Will let you know when I find the explanation, which may be buried in Lal's work somewhere. Still, I wonder what biochar does to the equation...

    But to restate, the challenge lies in implementation, which isn't just about measuring soil carbon in one spot. Besides modeling issues, there are issues of demonstrating that emissions aren't merely being displaced (i.el, leakage), additionality (the farmer would not have done it but for the credits), and permanence for however long is required by the standard. At least in the US, quick turnover of land ownership, which disincentivizes any form of long term commitments that restrict land use practices. On my "to read" pile is information on the latest in the development of regulatory protocols for agricultural carbon projects by California, and to see what progress has been made on some pilot projects. Projects using a more rigorous standard, or higher bar than did CCX, can get a significantly higher price, even on the voluntary market, but developing those projects is an expensive and mindboggling process. And risky in the absence of a national or international climate policy. But perhaps successful demonstration projects and innovative regulatory programs in smaller jurisdictions such as California will link up and will lead the way in a more bottom up way.


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