5 min read

Carbon Capture and Removal with Biochar

A picture of biochar

In my previous article, where I wrote about buying carbon offsets, I made the case for the importance of durable offsets: it's crucial that the carbon dioxide you pay to get sequestered is not in risk of leaking back into the atmosphere after a couple of decades. Trees fall (no pun intended), by nature, into the lower end of that scale and more advanced methods like mineralization and geological sequestration fall in the higher end.

But there is a problem, or rather an expected result of the market needs around durable offsets: there is a huge supply of cheap forest and agriculture credits in voluntary markets whereas you can only hope to be as huge as spotify or microsoft in order to get some looks in the millennia-scale class of offsets (geological sequestration and mineralization with DAC, BECCS). This picture is not bound to change as experts state that we are still at least a decade away from affordable DAC offsets (climeworks currently charge 1000€/tnCO2, whereas nori with their regenerative agriculture projects charge 15$/tnCO2).

Biochar's potential for carbon capture and removal

Enter Biochar, the hot cousin of charcoal that gets created in high temperatures (700C) in low or zero oxygen conditions. Or reenter, Biochar, because it turns out that it's not a new thing. Here's a short history lesson:

  • First, thousands of years ago, Amazonian natives burned wood and other biomass in deep pits, then scattered the remains across their soil to improve their fertility.
  • Then, in the seventies, the back-to-the-land movement labeled biochar as their rebellious act against industrial mono-culture agriculture, by making their own biochar and using it instead.

And, now, in the heat of carbon removal we have companies that are rediscovering biochar as product not for soil improvement, but as a reliable carbon removal offset option. Here's an unscientific, but kinda accurate diagram of where carbon removal offsets fall:

A chart mapping permanent and short term carbon removal pathways like dac, mineralization versus forests, soil and how biochar sits in the sweet spot between them
Upper right position is better with a preference to "upper"

Biochar can hold its captured carbon dioxide for centuries or even thousands of years, so it sits in that sweet spot between the few but long-term removal companies and plenty but short-term capture forest offset companies.

And more attention seems to fall upon this industry, so that blue cross is going to move further to the right. You don't believe me? Ask Segment's former CEO who, in a Michael Jordan hiatus like move, changed an entire sport and assumed the CEO role of Charm Industrial:

How do you make Biochar?

There is one main process that is involved in making Biochar, which is Pyrolysis. Here's how it works:

  • Take any kind of biomass, trees, branches, leaves, other agricultural waste, nut shells, corn, wheat, basically any organic matter that has Carbon in it and that is, preferably, not alive or has any other useful purpose (like food). Considering that global crop residue is at around 5.5 billion tons per year, and that a ton of biochar can hold about 3.5 its weight in Carbon Dioxide, you can imagine that the potential is huge - until you realize that all this residue is not gathered in one place, so you will either have to create a lot of small facilities and use land for this specific purpose (and the side effect of creating bio-oil).
  • Then burn it in 350C-900C with no oxygen and product biochar and a lot of gases which can be condensed into liquid bio-oil, so you also have this side benefit. This is Pyrolysis, and as such high temperatures are involved, you can bet that you need to use renewable energy in order to be able to sell those carbon offsets.

While it sounds like you can do this process at home (and you can), there are some issues that can trip you up, if you plan to do this at scale:

  • Consistency in production is difficult, as you have different type of feedstock with varying levels of humidity, temperature and residence time.
  • If you plan to sell offsets, you need to scale a lot otherwise selling it at 100$/ton will not suffice when it costs you 300$ to make it.
  • Selling it as a soil amendment solution is actually trickier than it sounds: it's not enough to just throw it to the ground but it needs microbial and nutrient enhancement (some feed it to their animals first before it's being passed out from their system, rich in N and P, to the soil).

And these are the tip of the iceberg, read this great article from "The Burning Question" to understand that while it's easy to create biochar in your garden, it's not the same game if you want to do this at scale and sell either offsets or agricultural products.

Here's also a nice video that I found that explains how a Pyrolysis Kiln works:

What does the Biochar industry look like

This is by no means an exhaustive list but here's an airtable of all the biochar companies I could find in:

  • Stripe and Microsoft's offset purchases in the past years.
  • Puro.earth in which they have 24 Biochar projects across their CORC and pre-CORC market ("certified" and "not yet certified" projects)
  • Wren (they have one Biochar project)

If you have one that you would like added, let me know by sending an email at hello@carboncaptureexplained.com.

If you want a list of biochar producers who are not necessarily selling offsets, you can also have a look at this list from Energy XPRT.

This seems to be a very exciting industry to watch. Just the carbon sequestration potential alone is exciting as it seems to win in both the capture and the removal bits against the other technologies:

  • It's less expensive than DAC, it's more tested (for thousands of years) and less complex technically (Nature basically does the capture part for us).
  • It's more durable than trees and regenerative agriculture in a very meaningful scale for the context of climate change (we know that we need to reduce emissions in the next couple of decades so we need at least a century of removal).

One caveat is that in order to sell these offsets you first need, for regulatory reasons, to sell the actual soil improvement product. This is viewed as a blocker by some companies in the industry and it's also a reason why you don't see any companies only doing offsets (and burying the biochar for example).

Lastly, Biochar's magic porous nature which acts beneficially to the soil also has another use: water filtration via adsorption. When I read that, I wondered whether its adsorbing capabilities could be used in another familiar use case to ours: Direct Air Capture.
It turns out that I'm not the only one with that thought, and I promise to you that this will be another article in the near future.