looking for recalcitrant molecules
July 28, 2021 2:56 PM   Subscribe

How much carbon could soil actually sequester? Despite rising enthusiasm for carbon farming in Europe and the U.S., some soil scientists are less optimistic about the climate impacts of soil carbon sequestration. Projects such as the Harnessing Plants Initiative and the Marin Carbon Project have multiple worthy goals but may be overstating the actual carbon sequestration benefits. “I have The Nature and Properties of Soils in front of me — the standard textbook... The theory of soil organic carbon accumulation that’s in that textbook has been proven mostly false … and we’re still teaching it.” posted by spamandkimchi (13 comments total) 10 users marked this as a favorite
Well it s probably something we should do anyway, If we want to keep eating
posted by eustatic at 3:00 PM on July 28 [4 favorites]

I imagine the numbers will be a sight better than industrial CCUS. Currently proposals on the US Gulf Coast will emit. L

Like Venture Global LNG, a net emission of 12 MTCO2e/ yr. rather than sequester anything, industrial carbon capture, as proposed, will increase emissions
posted by eustatic at 3:05 PM on July 28

Recommendations on carbon farming from the Breakthrough Institute article:
... we should not incentivize agricultural practices that reduce yields and lead to land-use change with outsized GHG, habitat and other environmental impacts. Instead, indirect land-use change should always be assessed — and assessed conservatively — when incentivizing agricultural practices.

... soil carbon sequestration should be treated very carefully and critically in any carbon market such as the California Cap-and-Trade Program. Given the large and compounding uncertainties — due to measurement, leakage, permanence and additionality issues — agricultural carbon sequestration should potentially even be excluded from such markets.
posted by spamandkimchi at 3:07 PM on July 28

Yay! Let's talk carbon cycling. Literally my favorite topic.

A harsh assessment of soil carbon sequestration from a biogeochemist.

Bill Schlesinger literally wrote the book on this--his textbook Biogeochemistry: An Analysis of Global Change (now coauthored with Emily Bernhardt) is the main textbook used in every graduate level biogeochemistry course. He also did a lot of the foundational work on the terrestrial carbon cycle (Emily is a freshwater scientist and likes nitrogen more than carbon, but we don't hold that against her).
posted by hydropsyche at 3:58 PM on July 28 [9 favorites]

Third link is broken, here's the proper link:

posted by deadaluspark at 4:44 PM on July 28

Is this as simple as the fact that there was/is so much carbon contained within fossil fuels that realistically to make a substantial dent in the problem it has to be put back underground in such a huge quantity that things like soil sequestration are like approaching a oil well fire with a drinking cup of water? I ask sincerely.
posted by Pembquist at 5:11 PM on July 28

Often the larger problem is that soils can give up their carbon when we don’t expect it (or due to,say, drought). Some of it is the scale problem too.
posted by clew at 5:44 PM on July 28 [3 favorites]

When I was an EMT we used to have a saying "it sure is easier to put stuff into a body than it is to suck it back out". I feel like this is similar. Nonetheless I'm excited to see if this technology can advance further.
posted by poe at 11:42 PM on July 28

Thanks for posting spamandkimchi, a vital topic.

Carbon geo-soil-fungi-plant-water chemistry is so complicated (I don't think we know enough yet to call it complex; it is, but complexity implies we have a clue).

I've been trying to get government here NZ interested in deep soil storage of so-called recalcitrant carbon species such as glomalin. Unfortunately they're ideologically opposed (pretty sure, I've taken this trail a long way here) as they want to favour NZ's really shitty forestry industry (mostly Pinus radiata). Also there's some worrying rewilding from the techbros and thoughtless greens and Greens. But much of our land was always grassland, well, at least since ~1000CE.

My exact text from a recent communication with our Parliamentary Commissioner for the Environment (PCE):
"The premise is that anaerobic and cool, deep soils >1m depth hold a lot of recalcitrant carbon fractions and their cooler, stable temperatures help retain carbon to millennia timescales.

Conversely ‘developing’ anaerobic soils ¹, or thoughtless tree planting would perturb these deep soils resulting in the loss of their total C storage ².

The other side of this is political\social engagement; yes results are needed but who carries them out? Removing farmers' agency and some degree of control from farmers disincentivises them – for a farmer the idea that they can help recover C where they are is a big part of the mentality of the modern farmer.

Carbon as an issue needs to become almost a religion, deeply embedded in culture, life and business; intergenerational family farms could be the forefront of this shift.

1 Kuiluweit et al. 2017 Anaerobic microsites have an unaccounted role in soil carbon stabilization., Nature Communications/pdf

2 Shahzad et al. 2018 Root penetration in deep soil layers stimulates mineralization of millennia-old organic carbon. , Soil Biology and Biochemistry/pdf - I have a full text of this is anyone's interested, a key line is "Deep roots stimulated microbial mineralization of ∼15,000 years old C."
posted by unearthed at 1:20 AM on July 29 [6 favorites]

Is terra preta a known example of storing carbon for hundreds of years? Or does it not actually do that once you look closely at its carbon flux?
posted by away for regrooving at 11:12 AM on July 29

What I took from this is that we can't just "store" carbon in soil. We need to keep a thriving ecosystem alive on top of the soil, or else the carbon will leak out over time.

Basically we need to live inside an ecosystem, not just treat the world like a storage tank for our waste.
posted by stilgar at 11:48 AM on July 29 [6 favorites]

(Terra preta is also an example of increasing biological activity by adding bioavailable material -- if carbon content remains high over time, it's a dynamic outcome, not cold storage. But there's also a fair level of woo in the literature and I'd be interested in a direct look at: just how long do the charcoal particles last? Where does their carbon go? What carbon influx occurs by what biological processes?)
posted by away for regrooving at 12:08 PM on July 29

We need to keep a thriving ecosystem alive on top of the soil

It also works to detach the buried carbon from any busy ecosystem at all, which naturally happens with oxygen depletion - logs that sink in cold lakes, or peat bogs. Such a surprise, peat bogs! Lively on the top, compressing millennia of their dead undecaying ancestors. Drain them and you get deep fluffy soil in a year, which rots away in a matter of decades because it has bio activity again. You can look down on some extraordinary cases of this in the Delta islands a bit upriver from San Francisco.
posted by clew at 11:46 AM on July 30 [3 favorites]

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