A soil-science revolution upends plans to fight climate change | Hacker News Reader

A soil-science revolution upends plans to fight climate change

quantamagazine.org

190 pointstheafh69 comments

There is one way of storing carbon in the soil for the long term: biochar[0]. Biochar is organic matter heated anaerobically (pyrolysis) until it turns into something like charcoal. Biochar is stable for a long time. You can then bury that in the soil... it seems to improve the soil by providing surface area for soil micro-organisms and to store nutrients. This could be done on a very large scale, and pyrolysis can actually be energy positive because you can burn the hydrogen that's released to perform the pyrolysis and still have energy left over.

This may be one of our best options, and we should accelerate more research in that area.

[0] https://en.wikipedia.org/wiki/Biochar

> still have energy left over

... if it's dry biomass.

Too much humidity might tip that the other way, unless I am doing the math wrong. Looking at CA's forests right now, that might not be a problem :/

Once bootstrapped, the excess energy can go into kiln drying the input for the next batch.

It doesn't automatically improve all soil, does it? As I recall it increases the pH level, which may or may not benefit the soil in that biome, or for the given use of the soil if you're growing food there.

The southern US traditionally has moderately acidic soils. Low soil pH is increasingly a problem in the Midwest as well due to poor agricultural practices.

This is an important point to consider. The agricultural studies I’ve seen typically apply 80% compost and 20% biochar to degraded soils because biochar is alkaline.

It can also be made less alkaline with better, more sophisticated production technologies (i.e., reactors) that minimize ash.

Why do you believe that micro-organisms will not break down biochar?

From the article:

> Yes, soil is enormously varied. And it contains a lot of carbon. But there’s no carbon in soil that can’t, in principle, be broken down by microorganisms and released into the atmosphere.

Biochar is interesting. It seems to be dependent on the temperature your pyrolysis occurs at and likely many other variables. It also encourages microbial growth that can help sustain and even add to the carbon content. There are studies that show it can sequester carbon from dozens to hundreds of years potentially, and patches of "terra preta" found in the Amazon are found to be self regenerating (growing at 1cm/yr) and were originally set down between 450-950BCE. Fascinating stuff.

If biochar is made with 80% or higher fixed carbon it has half life of >500 years in active agricultural soils.

If you have to, you can store it in underground mines.

The result effectively reverse coal mining.

we could skip out the middleman and just leave the carbon in the ground to begin with.

Probably too late for that.

If by "we" you mean everyone, no we can't.

Edit: assuming you know it's too late not to start, propose something other than magic wand obvious solutions.

We could stop all fossil fuel burning today, and we would still need to sequester carbon.

Compared to time travel, carbon sequestration is easy tech.

And you would need nothing less than time travel in order to persuade the mining companies of the 18th-20th century not to mine coal.

Biochar is pyrolyzed lignin, lignin is notoriously difficult to break down

… and while fungi have certainly figured out the lignin thing, pyrolyzed anything is much harder to break. Unlike fresh organic stuff, most of the N, even O and H is gone. It’s just more favorable to eat something else.

The process removes almost everything except the lignin, leaving the same lignin structure - but broken and slightly hydrophobic from the residual creosote.

In principle slowing down the return of carbon back to the cycle is helpful, even if it isn’t a permanent solution. In many ways this is exactly what trees are; a way to convert a ton or so of fast cycle carbon into wood that will retain it for a century or so.

Of course, the numbers matter. I can’t speak to Biochar, since it might not hold onto the carbon long enough.

Pure carbon is already pretty much broken-down, chemically, unlike longer carbon-based molecules.

You can still oxidize carbon, to form CO2, rather than ... probably graphite or similar forms.

Plants themselves don't do much with soil-based carbon. I'm not sure what the microbial activity based on it would be.

The science does not meet the hype.

> Our review shows there are not enough data to draw conclusions about how biochar production and application affect whole-system GHG budgets. Wide-ranging estimates of a key variable, biochar stability in situ, likely result from diverse environmental conditions, feedstocks, and study designs. There are even fewer data about the extent to which biochar stimulates decomposition of soil organic matter or affects non-CO2 GHG emissions. Identifying conditions where biochar amendments yield favorable GHG budgets requires a systematic field research program. Finally, evaluating biochar's suitability as a climate mitigation strategy requires comparing its effects with alternative uses of biomass and considering GHG budgets over both long and short time scales.

From https://journals.plos.org/plosone/article?id=10.1371/journal...

That paper is from 2013. The science has advanced substantially since then.

Several university laboratories are still actively researching biochar and provide snapshots of the current thinking regarding its usefulness:

https://whitmanlab.soils.wisc.edu/faqs/

http://www.css.cornell.edu/faculty/lehmann/research/biochar/...

Honestly not too far from the glib “just bury the coal again” solution.

Another example of an article selectively picking bits and pieces to support a sensational and false conclusion. The discussion of oxygen exposure was conveniently left out. Why focus so much on the concept of recalcitrant carbon when microbes will break down rock and even petrochemicals under the right conditions?

Oxygen is a dominant factor in accelerated decomposition. Carbon is continually sequestered in healthy soils where plant roots will die back periodically, both seasonally and from grazing action. Much of the spent root carbon is sequestered in the soil as the limited local oxygen is used in partial decomposition, replaced with gases that serve to preserve and dilute whatever small amount of oxygen may later infiltrate the soil, depending on depth in soil.

This is the same concept seen when lacto-fermenting vegetables in a jar. Enough salts would effectively halt decomposition, but just a fraction of the salt is needed when the CO2 generated from the lacto bacteria flushes out the oxygen. The rising acid and falling oxygen gradually drive the microbial activity toward zero.

Lack of oxygen may make it even worse. Evolution of methane from decaying organic matter in soil in an anoxic environment would be much worse than CO2 in terms of global warming.

However, I’m not a soil scientist.

Methane production requires nearly a total anoxic environment. Even trace amounts of oxygen are enough for substantial suppression. Decaying roots, even if they were deeper, would be exposed to at least a little oxygen throughout the early decay process (unless continually flooded with water). Once the roots have decayed to a stage where they are more decay resistant, there would naturally be even less local oxygen, but they would also be in a state not favorable for substantial methane production.

The chemistry seems complicated. To create methane, you need hydrogen, which is a byproduct of previous anaerobic microbe activity. Think lots of fresh plant material decomposing in an anaerobic environment.

"One teaspoon of healthy soil contains more bacteria, fungi and other microbes than there are humans on Earth. Those hungry organisms can make soil a difficult place to store carbon over long periods of time."

The natural respiration of soil microbes is small compared to how much carbon can be naturally sequestered in healthy soil due to sustainable agricultural practices.

Healthy soil is well-known to hold substantial amounts of carbon, right along side such organisms. The development of unsustainable agricultural practices (monocultures, single-planting seasons, letting fields lie fallow, tilling, chemical sprays, essentially Monsanto's entire business model) has destroyed soil biodiversity and health. Healthy soil can absorb an inch of rain every few minutes. Fields flood (and crops are subsequently lost) because the ground is hard and crusty, preventing soil absorption. If more cropland soil had the healthy consistency of cottage cheese, flooding wouldn't be an issue.

Yes, forced carbon sequestration might not work in the presence of healthy soil. However, fixing the deficient soils created across the world from unsustainable industrial agriculture practices will naturally sequester carbon. I would love to know exactly how much carbon no longer is trapped in our soils that once was due to the last 100+ years of unsustainable industrialized agriculture.

https://www.youtube.com/watch?v=uUmIdq0D6-A

https://microbiometer.com/improving-soil-health-and-carbon-c...

As someone who has practiced (or tried to) sustainable agriculture in the tropics, I have to say that I've long ago become dubious about the whole idea of storing carbon in the soil. I think in cold climates, under dense forest growth, maybe more carbon accumulates than the microbial life can consume, up to a point, but in the tropics that sure doesn't seem to be the case. Most of the soils I've seen have essentially no carbon content below the first few centimeters... all the nutrients are in the litter layer above the soil, and most of the native plants will grow their feeder roots right into that litter (mulch). With a lot of effort and a lot of mulch, you can start to accumulate a bit more carbon in the soil, and a lot of crop plants sure appreciate that, but by far most of your mulch is going to disappear amazingly fast if you don't keep applying more, and then that bit of soil carbon quickly disappears, too. You can't build those deep, black, "healthy" soils you see in temperate climates in the tropics. At a guess I would say 99% of the carbon in tropical rain forests is in the living matter.

And the problem is that with global heating, the tropics are on march toward the poles.

It seems that the rich black soil in the Amazon was man-made and has lasted thousands of years:

https://en.wikipedia.org/wiki/Terra_preta

Right. That's biochar. See my top-level comment.

But note that this is not all or most of the soil in the Amazon, by a long shot... the "terra preta da Amazonia" exists in isolated patches where humans had been conducting slash-and-burn agriculture for hundreds of years. Most of the soil of the Amazon region is just like any other topical soil, nutrient and carbon poor.

But biochar establishes the fact that carbon can be (semi-?)sequestered by a sustainable human agricultural process, this scheme has been implemented on a large scale in the past, and similar schemes could be implemented in future ag systems. That’s not a trifecta you hit very often in complex systems of any sort.

Upshot: if you are a young scientist/engineer/agronomist/ag economist and want to do real hands-on exploratory science where everybody is in the dumb club, and still make a significant direct middle/long-term difference in the world and its population, soil science could be your ticket.

PS: The content of the article is great. The click-bait title is absurd.

This is interesting to me. For the past 15 years I have had a small plot in the tropics on which I have tried to improve the soil by adding copious amounts of compost, manures and growing cover crops that I till under. All that organic material just seems to disappear quickly. Before I owned it the plot was planted with corn and sugar cane each year and lots of chemical fertilizers and pesticides were used. So the soil was ruined. I thought I could bring it back within a few years but it is still rather poor. There was one patch that looked much better after a giant pile of scrap wood left over from house construction was burned and the left over ash and char was plowed in. But that did not last long. It is all back to hard crusty soil now. The pH is rather high due to the high percentage of karst in the region and the high calcium carbonate content of ground water that is used to irrigate. Maybe that has something to do with it?

I think your experience is just normal for the tropics, and it has nothing to do with the specifics of your soil. Certainly I and lots of others have had similar experiences.

In natural tropical environments the nutrients aren't in the soil, they are almost all tied up in the living biomass, and as soon as some of that dies the nutrients it releases are absorbed by other living vegetation. And generally, if we want to do things in a way that's sustainable, we should look to nature and try to imitate it (and once we can manage that, try to improve on it).

What I've found is that the only way of doing tropical agriculture that's remotely sustainable is "slash and drop" agroforestry, which is where you interplant (a lot of) biomass for mulching together with your crop plants and keep cutting/pruning that to produce mulch, so that you can keep your crop plants heavily mulched all the time. This is fairly labor intensive, though, and worse, it requires highly knowledgeable labor to maintain.

That is very interesting. What are the preferred plants to grow to produce the biomass for slashing and dropping?

There are too many to list, and it depends entirely on the crop system you're trying to support. For example, for annual crops it would be different than for multi-year agroforestry systems, and you may want some plants to provide windbreak or shade for others at an early stage, and then remove them when others are more mature, etc. Also, you want a mix including some legumes for their nitrogen fixing ability. And some plants are better at utilizing and accumulating specific minerals (bioaccumulators), so may want some of those.

In short, it's complex and requires a good deal of knowledge or willingness to experiment, which is why it's not more widely practiced, even though when done correctly it undoubtedly is very effective, sustainable, and requires far fewer inputs than any other agricultural practices. At least in theory, a master of this art can design systems that are planted once and the produce different crops for several years while mimicking the natural succession of a grasslands in transition to becoming a forest with a fairly small amount of maintenance (harvesting crops at different stages and chop-and-drop'ing mulch plants). One master of this art here in Brazil, whom I've learned a lot from, is Ernest Götsch[0][1].

[0] https://agendagotsch.com/en/

[1] https://en.wikipedia.org/wiki/Ernst_Gotsch

Money quote:

«But over the past 10 years or so, soil science has undergone a quiet revolution, akin to what would happen if, in physics, relativity or quantum mechanics were overthrown.

...

Soil researchers have concluded that even the largest, most complex molecules can be quickly devoured by soil’s abundant and voracious microbes. The magic molecule you can just stick in the soil and expect to stay there may not exist.

...

The consequences go far beyond carbon sequestration strategies. Major climate models such as those produced by the Intergovernmental Panel on Climate Change are based on this outdated understanding of soil. Several recent studies indicate that those models are underestimating the total amount of carbon that will be released from soil in a warming climate. In addition, computer models that predict the greenhouse gas impacts of farming practices — predictions that are being used in carbon markets — are probably overly optimistic about soil’s ability to trap and hold on to carbon.»

This is being used beneficially at some superfund sites- they basically wait for some natural microbe to emerge that neutralizes or otherwise treats the prevailing contaminant, sample it, figure out how to maximize it's metabolism, then devise a way to assist the in situ conditions to become ideal. Maybe some wells, pumps, plants, or chemicals are installed/introduced, and then it's just a monitoring expense.

This is an approach I have seen first hand in my professional life. We have isolated multiple strains of beneficial microbes from contaminated sites (primarily hydrocarbons) for use in remediation efforts. These microbes are very capable and have abilities beyond say the degradation of benzene…for instance they provide nitrogen fixation or phosphate solubilization or other plant promoting activities which allows us to use the same isolates in agriculture to promote a more sustainable production system. I believe microbes play and will continue to play a fundamental role as we find the balance between lowering the impact of commercial agriculture while ensuring the agronomics of said production.

Biochar.

It lasts for at least a couple thousand years, and is considered a long-lasting soil amendment.

The presence of biochar creates habitats for those microbes and conserves nutrients, making the soil fertile, even in areas like the Amazon where rainfall normally washes away nutrient accumulations. It can be made with processes that sequesters carbon, both in the charring stage (via gassifier designs optimized towards sequestering) and during the inoculation stage where it can capture greenhouse gases emitted by a compost pile.

This sounds really interesting. Do you have any reading recommendations (links or books)?

I found these videos very interesting:

https://www.youtube.com/watch?v=svNg5w7WY0k&t=5s

This is on my to-do list:

http://climatechangeacademy.com/courses/carbon-removal/4

https://bootup.airminers.org/

I found a lot of information from comments here:

https://news.ycombinator.com/item?id=27822694

I can also recommend this wikipedia article and its surroundings:

https://en.wikipedia.org/wiki/Terra_preta

As others have noted, the wikipedia entry is a great resource.

I was introduced to it on this podcast episode: https://podcasts.apple.com/us/podcast/permaculture-for-the-f...

Burn, by Albert Bates and Kathleen Draper (2019) - goes into the multitude of ways biochar can be utilised. It's a bit heavy, but in a good (here's the research that backs us up) way.

https://www.chelseagreen.com/product/burn/

Some studies are quite skeptical. For example,

https://asi.ucdavis.edu/news/new-study-biochar-helps-yields-...

https://journals.plos.org/plosone/article?id=10.1371/journal...

Some studies even show that biochar soil amendments accelerate the breakdown of humus and release net positive CO2 to the atmosphere:

https://onlinelibrary.wiley.com/doi/full/10.1111/gcbb.12376

> However, soil CO2 fluxes were suppressed when biochar was added to fertilized soils, indicating that biochar application is unlikely to stimulate CO2 fluxes in the agriculture sector, in which N fertilizer inputs are common.

> Our results showed that biochar application increased soil CO2 fluxes by 43.33% in unfertilized soils, but decreased by 8.61% in N-fertilized soils, consistent with the meta-analysis of Liu et al. (2016).

The metastudy did go into detail about N2O and CH4 as well in both fertilized and unfertilized soil.

The soil exhaustion per a kilowatt hour given the planet's primary energy consumption is problematic and doesn't shift.

3-5% of all natural gas is used for nitrogen fertilizer production and 50% of the food mankind eats requires it.

When all the folks keen on approaching mankind's environmental problems think from a framework of minimizing CO2 emissions, they often miss out on things like nitrogen trifluoride and sulfur hexafluoride, which have significant global warming potential and are used more frequently as institutions use the objective function of (min(CO2 emissions)).

Is biochar a potential solution?

The first study I found on google seems to suggest that biochar lasts for a pretty long time but also decomposes: https://www.sciencedirect.com/science/article/abs/pii/S00380...

If I'm reading that correctly, they say it should last about 4,000 years which should get us pretty far.

Bluntly, yes it is.

I'm surprised that they didn't find long lasting plastics in the soils

Maybe they didn't look for it?

Makes sense, and underscores why the loss of permafrost is catastrophic. Cold conditions impede the activity of microbes that metabolize soil.

A pipe-dream like planting trees.

GM bio CCS using aquatic life is the way to go because the carbon can be easily sunk fown into deep trenches without worrying about it returning the the carbon cycle.

well at least we can all agree the climate models are wrong.

TL;DR

Lets bury our carbon waste using plants, not address the issues that we're burning fossil fuels and creating carbon waste at an increasingly alarming rate or focus on renewable clean recyclable energy...

Hm. I perfectly understand cynicism, because I'm very good at it myself. (At least I think so.)

However, in this case I'm of a different opinion. Let's put aside the sluggishness of going totally green/eco/sustainable/whatever for a moment and think about what would happen if we managed to do it in an instant, like now.

Then this would still be a usable and sensible thing to do, because right now it looks like we are very, very late to the game, and every little thing counts.

In my opinion this would even make sense if produced as sort of artificial zeolites produced by atmospheric carbon capture by whichever industrial process, even nuclear powered.

https://en.wikipedia.org/wiki/Zeolite

edit: thinking about it, though slightly off-topic in this context is another path to carbon sequestration I remember:

https://en.wikipedia.org/wiki/Project_Vesta via spreading this stuff on beaches: https://en.wikipedia.org/wiki/Olivine

Green Beaches!

For your amusement: The Fifth Element-Green 1m4s https://www.youtube.com/watch?v=lFeLDc2CzOs

Word Up? https://www.youtube.com/watch?v=MZjAantupsA 4m39s

This totally ignores what happens to dead biomass in the very long term. It turns into coal. If that's not sequestering carbon I don't know what is.

Isn't coal from before dead biomass could be decomposed?

Yes

While there's a hypothesis that lack of lignin-eating bacteria/fungi spurred greater coal formation at one time in earth's history, there's not much evidence supporting it.

Rather, general conditions during the paleozoic/mesazoic periods (shifting waters, tectonic movement) likely lent themselves to accelerated coal formation as plant matter was disturbed, submerged, and interred in greater amounts than occurs today.

No. There are two prevailing theories of how coal is formed - Drift or In-Situ but in both, coal is plant matter decayed (via bacteria, fungi etc) into peat. The peat then undergoes the transition to various coal forms (Lignite, Bituminous, Anthracite) due to pressure as it sits underground.

It's a very slow process, but ongoing.

Once I visited a lignite coal mine in western NoDak. The owner was fond of showing a collection of semi-fossilized root balls and tree-parts that were dug out along with the coal. Dates to 55-65Mya.

It was being strip-mined, and it was close to the surface too. "Western North Dakota contains an estimated 351 billion tons of lignite, the single largest deposit of lignite known in the world... enough to last for over 800 years..." - https://www.dmr.nd.gov/ndgs/Mineral/nd_coalnew.asp

Aside from time, you also need a stricly anaerobic environment under pressure for that to happen.

> Indeed, radioactive dating measurements suggest that some amount of carbon can stay in the soil for centuries.

This is the only quote that matters. We literally know it works.

Yet the world is so so broken the facts don't matter.

We have the observable working model, but the environmental industrial complex needs to keep its minions in a constant state of panic which allows it to keep its control.

A healthy human being would see this article as how amazing our understanding of soil science is getting.

Just last week there was an article on increasing plant root length and increasing productivity that's working in field tests. Increasing soil depth just a little in farmland is a huge change. Nothing is upended. https://www.nature.com/articles/s41587-021-00982-9

This is interesting around invasive species https://onlinelibrary.wiley.com/doi/10.1111/gcb.15769

What that quote doesn't tell me: if I bury carbon today, will 99% or 1% of it stay for centuries?

Exactly. That should be the most basic starting level.

And obviously we don't need centuries, 50 years is enough.

It's all set up for fear.

Reply on news.ycombinator.com