Carbon Sequestration

[Ochre_face]

There's still a hell of a lot of potential in ecosystem restoration.
I'm working with a program now that's applying for VCS (Voluntary Carbon Standard) accreditation and their preliminary estimates are ten million tonnes over the next thirty years, over a few tens of thousands of hectares. That's just from the grazing and range management, they're not including the wetlands and cultivated lands.

Actually achieving that is going to be a challenge, but it's the whole point of the project and they're an experienced outfit.

I have a few problems with VCS and most of the other carbon accreditation protocols like REDD+; there are some face-palmingly stupid requirements in there which is what happens when you have people in Geneva (or whwrever) setting protocols for every biome and country. But most of it is pretty sensible.

There are millions of square kilometers of degraded land around the world that should be targets for restoration projects.

It's no silver bullet - much of the carbon they sequester, even if theyre successful, is simply the carbon that was released when they were degraded in the first place. But a huge amount of atmospheric carbon does come from land use, and has signficant benefits for both water and food security.

 

[Ochre_face]

Not quite demultiplexer. As I've pointed out before, there is an enormous quantity of alien invasive and bush encroachment biomass to be harvested, on the order of billions of tonnes. Invasive or encroaching woody plants have impacted millions of square kilometers. The biomass can be used for energy production and biochar.

It would be a small percentage but a very, very useful supplement to other efforts, with the quadruple bonus of energy, land restoration, and a lot of jobs in a lot of places, plus carbon credits.

Unfortunately some of the current carbon standards like the one particular VCS I'm working with don't recognise indigenous or alien invasive plants as a valid source, but that's an administrative issue that I think is being rectified under newer standards.

 

[Ochre_face]

Everything is a drop in the bucket. All the options are cumulative and there's no universal silver bullet tech that I'm aware of that can single-handedly pull hundreds of billions of tonnes of CO2 out of the atmosphere and sequester it, at least not without significant other costs including environmental.

So far both of the natural options I've proposed have the potential to cumulatively "make a dent" in atmospheric carbon. Combined with other technological solutions those dents can start adding up.

Currently there's an excess of about 300 Gigatonnes of carbon in the atmosphere, nearly a third of which comes from land degradation. Land restoration has the potential to pull most of that third back, so around 70 billion tonnes of C or thereabouts.

Biochar has the potential add a few billions to that, partially through the same land restoration programs since woody plant encroachment is both a major driver of and response to degradation.

 

[Ochre_face]

I didn't want to derail this thread with natural carbon, just add options that hadn't been considered and which are currently being implemented at scale in the case of land restoration. Have been for decades. The land restoration projects are offsetting, or being offset by depending on your POV, the land degradation projects. But they're happening today. In fact natural carbon restoration and improved agricultural practices are the only mass-scale carbon sequestration projects happening at all. None of the technological approaches are being done at scale yet.

Biomass to energy isn't being implemented at scale for carbon sequestration, but billions of dollars are being spent on invasive plant control world-wide so the mechanisms are already in place for harvesting.

Natural carbon sequestration currently is on the order of about 30% of fossil carbon emissions annually, mostly unintentional. Bumping that up by a few percent gives a billion or so extra tonnes, or about as much as mining and crushing a few hundred billion tonnes of basalt.

Basalt's potential was estimated at 2.5 billion tonnes CO2 per year in this article. Their numbers were 5kg/m2 of basalt, or 5000 tonnes per km2, on 55 million square kilometers.

That's 275 billion tonnes of basalt to remove 2.5 billion tonnes of carbon dioxide per year.

Meanwhile one of the projects I'm currently working on is anticipating about 300,000 tonnes of carbon dioxide sequestered annually over a few thousand square kilometers with zero major inputs. Mostly just management effort. That doesn't include the potential for the cultivated lands which are excluded from the project.

Technological solutions also need to be implemented but the scale and challenges are just as staggering.

 

[Ochre_face]

Fortifying soils comes with a bunch of secondary ecological effects, many of which are undesirable. The ecosystem and plant community has evolved to the soils that are there and shifting soil chrmistry and structure can dramatically shift the relative competitiveness of different species which can completely change the structure and composition of the vegetation.

I don't know what the effects would be and I'm not aure that anyone does at this stage. They'll differ enormously from one location to the next even within a few kilometers - sandy versus clay, acid versus basic soils and so on.

Start on cultivated lands first with trials on natural vegetation until we have a better handle on that.

 

[Ochre_face]

Thanks. I'll try download the full paper when I get a chance.

 

[Ochre_face]

But it does like the surface area of biochar.

I found this literature review of the effects of biochar on soil biota. It varies a lot according to the quality and type of biochar, such as what feedstock was used and how it was pyrolised, and the soil biome also changes over time as the surface characteristics change. Not all biochars are equal, higher porosities are key to increasing the population of soil microbes.

https://scholar.google.co.za/scholar?q= ... x90j2mhYcJ

 

[Ochre_face]

I'm a bit late to this conversation, but I saw this

To start with fire: biochar is a great way for short to medium term carbon sequestration. Burn down a couple forests, bury the carbon, let everything grow back, repeat. You can do about 500 tons per square kilometer per year in most regions, given enough water to grow the biomatter. The obvious downside is that this is pretty polluting and disturbing. For some sense of scale: there is about ~2500 gigatons of carbon to be sequestered, cumulatively over the next 50 years, so this requires about 50 Gt/year of sequestration or a permanent forest fire of about 50e9/500=100 million km2 or roughly 2/3rds of all the world's land, including greenland and antarctica. Yes, if you try to reverse a process that took 100k years or more in just a few decades, it's going to require some dedication.

Why are you burning these forests? Doesn't that turn cellulose into carbon dioxide? Wouldn't it be better to just grow the forest and bury it without bothering with the burning? If you're trying to compact it, shredding (or just steam rollers and similar heavy equipment) probably works pretty well. Making a wood fired steam engine shredder shouldn't be too hard if you really insist on using fire..

"Burning" is a poor description of biochar production. "Pyrolyze" is the word he should have used.

Yes, some carbon ends up as organic compounds that can be used as fuel or feedstock. The rest of the carbon gets converted to charcoal, which doesn't go anywhere for at least millennia.

Formation of biochar on the scale necessary for significant carbon sequestration would require actually burning forests. If you do it right, you can get pretty high biochar conversion rates, up to about 50% yield. Requires really intense fires in certain classes of trees. Naturally this has been observed in e.g. Utah and California wildfires.

Drying and pyrolyzing 10+ gigatons of biomass each year is currently beyond the scope of machinery we can employ. Total woody biomass harvesting in the world is around 1.5 Gt/a right now.

Pyrolysis of 1Gt/year, however, is within our industrial capabilities. There are gigatonnes of biomass harvested every year, of which a portion (the by products and waste) could be pyrolised or composted (some of it already is). Plus another gigatonne or so of biomass that should be harvested and can be turned into an economic resource rather than cost.

It would be counterproductive to start setting fire to more forests purely for carbon sequestration. There already is an economic model for the process with several revenue streams.

It doesn't have to solve the whole problem by itself. Just like emissions reduction, carbon sequestration is going to need multiple different approaches each contributing a small amount. Also like emissions reductions, sequestration will be distributed, with thousands of individually small projects adding up to billions of tonnes.

Direct air capture, as one example of a potential technology, would be made of thousands of plants scattered around the world, each of which contributes almost nothing but collectively pulling millions of tonnes of CO2. Assuming the technology takes off.

Same with basalt. We're not going to (or rather, we're unlikely to) mine hundreds of billions of tonnes of basalt. The world production of dimension stones, which includes basalt, was 160Mt in 2020.

https://www.brasilmineral.com.br/notici ... e-industry

I couldn't find numbers for basalt alone, but we'd need to increase basalt quarrying by three orders of magnitude - an effort that would take vast resources in its own right and have signficant environmental impacts. Quarry, crushing, transporting and spreading.

So we might be able to increase basalt production a hundred-fold to get to 10s of Gt, which in turn is a few hundred Mt/year of CO2 sequestration

Some of the other proposals mentioned upthread could potentially add a few Gt/year to the cumulative numbers. The constraint is going to be the same - how much of the feedstock/raw materials for the processes can we extract, process and distribute.

 

[Ochre_face]

I took a bit of a deeper dive into the company TSBasilisk mentioned on the first page (as deep as one can with a startup anyway): Brilliant Planet, the ones farming algae.

Dave of Just Have a Think covered it, and interviewed the founders so has more details than most of the other coverage I've seen. Unfortunately he didn't share the actual interview.

For those who don't want to watch the video, the transcript is a short read (.docx)

To summarise:
1) select coastal desert locations meeting the right criteria (flat, no conflicting land use, dry etc)
2) screen and isolate suitable local species and strains of algae
3) pump deep cold seawater from 1-3km offshore (the classic nutrient upwelling waters off many deserts)
4) Their process, they claim, doubles algal biomass every 2 days
First twenty days are indoors, starting in flasks and working up to indoor troughs, before spending the final ten days in outdoor ponds.
5) sieve and dry the algae under the desert sun
6) Bury it a few meters down.
7) Send the now decarbonised water back out to sea to absorb more CO2.

The burying approach is interesting. They claim four protections against rot at such a shallow depth
1) Firstly, under drying, proteins bind and resist decomposition
2) The location is a desert with very low rainfall
3) A geotextile membrane covering the buried algae for when it does rain
4) the high salt content of the dried algae absorbs a lot of moisture before it can available to microorganisms

They believe they can trade in the high-value end of the carbon market, currently at $100-200/tonne. Importantly, their approach appears solidly additional (carbon in desert sands that wouldn't otherwise be there) and verifiable (auditors can auger for samples). Also the lack of land conflict. The highest energy demand, the pumps, can easily be met by local renewable energy. Selecting local strains of algae means resilience and minimal risk of alien invasive species.

They're scaling up their Morocco test plant to a pilot plant with some seed funding, so it'll be very interesting to see how it pans out.

Total potential, based on suitable desert locations, is about 2 billion tonnes a year.

I gotta say, with all the usual caveats about startup claims, I do like the relative simplicity of this approach, and the business model. Verifiability and addionality are two very hard criteria to meet in the carbon market and they appear to have that.

 

[Ochre_face]

No bioengineering required. Just pick suitable species and varieties for the environment and get on with it.

 

[Ochre_face]

My biggest issue with burning is that, even though there is Pyrolysis and biochar left over, a huge proportion of the biomass is combusted. That's why I'd prefer to pyrolise harvested biomass, of which there is no shortage.

Hydrothermal carbonisation is another process that's getting a lot of attention recently, especially for things like sewerage sludge. The result is essentially a coal substitute and a bunch of byproducts. There are some companies working on actually making a coal substitute for renewable power, but it could just be buried.

 

[Ochre_face]

I started typing this last night before I went to bed and before demultiplexer's post.

We routinely appropriate and handle billions of tonnes of biological carbon every year - 15 billion tonnes or a quarter of global NPP. Note that we don't handle all of that carbon directly but we do get our actual hands on very large quantities of it. If I'm reading their supplementary materials correctly (Table S1), we consume 589kg/cap/year which is 4.4 billion tonnes of C per year or around a quarter of the quarter. Lets say a quarter of that or a billion tonnes of C is usable waste and we can divert a quarter of the usable waste, or ~250 million tonnes of C. That's a billion tonnes of CO2 per year.

So a quarter of a quarter of a quarter of our Human-Appropriated Net Primary Production would be equal to spreading 100 billion tonnes of basalt over 25 million square kilometers, or putting algae farms on half the world's suitable coastal desert areas.

And we can do that easily by adding a simple waste processing step along various stages of the biological carbon supply chain and by natural restoration projects.

Now that, as demultiplexer correctly points out, is only a fraction of what we need to achieve. The total CO2 that we need to remove is on the order of 1500Gt. At a few Gt/year, biomass alone would take a very long time. But it's also the only carbon sequestration happening currently at scale, and it's by far the cheapest of all the options. We will need major technological solutions to tackle the rest of the problem, whether Direct Air Capture or Direct Ocean Capture.

It diverts precisely zero effort from other initiatives, and in fact is badly underfunded at the moment. Dollar for dollar, the return on investment to society from better managing our natural (biological) resources is one of the highest of any interventions because most of the work is free.

As for reducing emissions - yes that is correct, and not a single person here has said otherwise.

Finally, demultiplexer, it's getting very frustrating watching you dismiss everyone's contributions here. I don't usually consider myself an "expert" in this topic - I'm a pretty journeyman ecologist - but I've been working in this field (agriculture and ecology) for over twenty years at scales from square meter research plots to entire countries (plural) and everything in between. What Tom and the others are trying to tell you is correct - we can trivially divert gigatonnes of biomass to carbon sequestration. It's the opposite of flashy, its available now, it's cheap and it's simple. And we do not need or want to burn down forests to do it.

 

[Ochre_face]

You're right, thanks for the correction on S1.

This IEA report from 2015 estimated 700-odd million tonnes of residue from harvesting operations (Table 7) (clearing, sawmill etc) worldwide. A signficant fraction, around 30-40%, of residue from clearing operations should be left on the land, leaving about 500 Mt of residue (70% of harvesting plus sawmill). The amount of recoverable agricultural residue is estimated also at around 500Mt (Table 9). I've seen other numbers for agricultural residue at billions of tonnes, which sounds reasonable since the IEA estimate was only looking at straw. This paper estimates agricultural residue from 27 crops at just under 4 billion tonnes, so between 500 million and a billion (my guess) should be able to be sustainably diverted, which is the same ballpark as the IEA estimate.

The WFP estimates 1.3 billion tonnes of food waste per year.

https://www.wfp.org/stories/5-facts-abo ... :text=1.,2.

Now, a lot of that waste is already diverted to energy and other uses. Its not all available. But there is still roughly a billion tonnes or more worth of biomass potential, or around a quarter to half a billion tonnes of C.

Thats excluding other waste bioproducts like feedlot effluent and sewerage. Feedlots are already diverting some proportion of effluent to energy and fertiliser but there's a hell of a potential there, and some sewerage is used for fertiliser but there's a lot of potential there too. That needs higher tech solutions.

 

[Ochre_face]

Yeah, that's one of those areas that I was following from my armchair for a while, and got despondent with the apparent lack of progress. Have there been some recent developments in algae for fuels in the last couple of years? From what I can tell there are some promising lab developments but not much more.