Biochar is destined to stay small
There's not enough land for Biochar to meaningfully scale
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In Part 1 in our series on Biochar, I wrote all about why this carbon dioxide removal (CDR) tech is gaining traction. To summarize, there’s a lot to get excited about:
Biochar delivers carbon credits quickly, often in <1 year
Biochar is relatively cheap, recently in the $25 - $100 range per ton of CO2
Biochar companies can sell two products: (1) their carbon credit product to businesses, and (2) the physical biochar product to organic farmers to improve their soil
Biochar does not require much up-front capital, which is why there are so many local and regional players entering the market
Now, given all the wonderful benefits that biochar has to offer, you might expect advocates to say that we should really just standardize on this approach to carbon removal, scale it up, and call off global warming as an issue. But no one is saying this. Why?
Biochar faces some hard but not insurmountable problems to scale. The logistics of transporting all that biomass is not negligible. And sourcing the right biomass is a real supply chain challenge — you don’t want to be known for taking logged trees and turning them into biomass.
But both of these problems can, and will, be overcome by companies with A+ supply chains. The real challenge facing Biochar is that we can’t cultivate enough land to make billions of tons of Biochar. This will keep Biochar small.
Let’s first cover biomass sources, since it’s critical to understanding the land-use issue, which I’ll cover in the second half of this article.
Sources of biomass
Biochar is a fairly straightforward process. From last week’s article:
Biochar is produced through a process called pyrolysis — we chop up the fallen tree and heat it up in a container with very little oxygen. Because there's not enough oxygen for the wood to burn1 completely, it doesn't release its carbon as CO2, and the carbon crystalizes into a stable form.
The question we have to ask is "what would happen to the biomass without an intervention from Biochar producers.” Let’s start with trees.
There are a few ways to get wood that you can feed into a pyrolysis machine to get Biochar:
Chop down trees and turn them into Biochar
Chop down trees in high-wildfire risk areas
Find dead trees
Chopping down trees that may live decades or centuries to make Biochar is very bad carbon accounting. And this is true even in high-wildfire zones where thinning trees cuts down wildfire risk. Yes, preventing wildfires is a net good. But the risk of a fire in that spot has to be balanced with the good that the ‘at risk’ tree can do for the ecosystem and for sequestering carbon.
As for dead trees, this seems like a huge logistics challenge. Are companies really prepared to go from forest to forest, lifting out only the recently dead trees? It would require a lot of infrastructure, from trucks to manpower, and high transportation costs.
It’s also worth noting that dead trees play an important role in forest ecosystems by adding nutrients back into the soil and providing refuge for animals of all kinds.
The bottom line is that if Biochar producers feel they must push volume to survive, incentives can get messy. I worry that as demand for Biochar ramps up, producers will get wood from less-than-savory sources. The risk with trees is too high — fraud just seems too easy — so trees should be off the table for Biochar producers.
So Biochar will probably have to rely on agriculture byproducts.
Crop stalks
Let’s turn to agricultural byproducts, and to make it more real, consider the stalks that come from crops like corn and wheat. Once the harvest is over, farmers have a few options for what they can do with crop stalks:
Burn them
Let them decompose in the open
Compost them
Use as building materials (e.g. as retaining structure for irrigation)
What farmers do with stalks varies widely. Open decomposition is quite common everywhere. In places like California, burning crop stalks is basically prohibited, and there’s a robust composting ecosystem in most of Western Europe and North America. In large parts of the Global South, burning or openly decomposing agricultural byproducts is more the norm.
Burning crops immediately puts greenhouse gases into the atmosphere. Decomposing out in the open, though less dramatic, is almost as bad.
It gets murkier with composting and the use of crop stalks in building materials. In both cases, there is some decomposition that will happen, but much of the carbon from these plants will return to the soil.1
If Biochar companies are certain that they are getting crop stalks that would otherwise burn or decompose, that’s good carbon accounting. Composting and building materials are more of a grey area. And the history of carbon accounting suggests that too much reliance on grey areas eventually creates scandals that destroy companies.
But let’s assume that Biochar companies can build great supply chains and get their hands on crop stalks that would otherwise burn or decompose. The question then is: how much of this actually exists? How much can realistically be turned into Biochar?
The problem of scale
It’s worth taking a step back to consider what kind of scale we need from Biochar.
In The Case for Carbon Removal, I argued that we should aim for carbon dioxide removal (CDR) at a scale of 18+ billion tons per year by 2040. Check out that article for the detail.
Let’s imagine that we want to make Biochar the cornerstone of our CDR program in 2040. Any target we pick here is arbitrary, given how little we know about the future and the development of other CDR technologies. But let’s say that we need Biochar to take out 12 billion tons of CO2 per year. Today, Biochar is in the ~200,000 ton per year range.
Here are some other assumptions:
1 ton of plant biomass generates 1 ton of CO2 credits
We switch from agricultural byproducts to a very fast-growing plant — like bamboo — that is specifically designed to maximize Biochar yield
One acre of land gets us 5 tonnes of plant biomass
Put all of this together, and we would need 2.4 billion acres of land. The amount of land under cultivation today is ~4.9 billion acres, so we’re talking about collecting all biomass from ~50% of the world’s farmland. That seems very unlikely!
Getting Biochar to scale up to even 1% of global farmland will be extremely difficult. That’s ~500 million tons of CO2, about the same as Brazil emits today. Impressive, but not enough to turn the tide in our fight against climate change.
Where would we put 12 billion tons of Biochar?
For the sake of argument, let’s imagine a world where companies have the tools to get all the extra biomass from 50% of the world’s farmland. That’s a world with highly automated electric tractors that not only clear farmland, but collect the biomass efficiently. And it’s a world of mobile pyrolysis trucks driving from farm to farm, year round, creating Biochar onsite.
Even in this world we would have a major challenge: where would all this Biochar go? It is far too much material for farmers to put back in their soil. And we don’t have a good place to put Biochar. Some suggest that concrete would be a good storage basin for biochar, but concrete has its own problems.
We have an excellent storage paradigm for CO2, because it can be compressed into a liquid and put underground, where there is plenty of space for it in emptied oil and gas wells. We have no such paradigm for billions of tons of what is essentially charcoal.
Any creative solutions?
The thing that I keep coming back to is how cheap Biochar is. And it is likely to remain cheaper than Direct Air Capture for a very long time. So we should be thinking hard about wild ideas to scale it.
Here’s one: how about growing plants that sequester carbon very quickly, harvesting them, and turning them into Biochar? It’s a middle ground between crop stalks and trees. I ran the numbers with bamboo, and it’s not pretty. We’d still have to use ~25% of global farmland just dedicated to bamboo to get to that 12 billion tons of CO2 removed. Again, very unlikely!
Ok, but what if: we built city-size vertical farms, often called arcologies, with 30+ floors, powered by giant arrays of solar panels and nuclear power plants, all to grow bamboo to turn into Biochar?
Now we’re in science fiction territory. Let me know in the comments if you have any ideas to make Biochar scale!
When we’re talking about our food supply, we shouldn’t just consider how effectively something removes carbon from the atmosphere — we want to encourage an awesome composting ecosystem.