Friday 10 November 2023

Making coal

Trees are very good at sucking carbon out of the atmosphere. Unfortunately, they eventually release it back into the atmosphere. Some gets stored for the longer term, but our ETS pretends it's all released at point of harvest. And there can be a good case for that if most of it does and if it's hard to track.

But there are other options.

I have no clue whether the economics of this option would stack up, but it should be allowed in principle.

Suppose a carbon forest owner harvested the forest, dug a very deep pit, put the harvested trees into the pit, and covered them with layers of clay so no gasses would seep up. The process takes carbon from the atmosphere and sticks it back into the geosphere. Give it time and it'll be coal.

I've always figured that if a carbon forest owner did that properly, that permanent sequestration ought to count against any surrender obligations that come with cutting down a carbon forest. For every tonne durably sequestered, a one NZU reduction in surrender obligation.

Turns out Bill Gates is backing a neater version of this. Story from December 2022 but I only just caught it.

A California startup is pursuing a novel, if simple, plan for ensuring that dead trees keep carbon dioxide out of the atmosphere for thousands of years: burying their remains underground.

Kodama Systems, a forest management company based in the Sierra Nevada foothills town of Sonora, has been operating in stealth mode since it was founded last summer. But MIT Technology Review can now report the company has raised around $6.6 million from Bill Gates’s climate fund Breakthrough Energy Ventures, as well as Congruent Ventures and other investors.

In addition, the payments company Stripe will reveal on Thursday that it’s provided a $250,000 research grant to the company and its research partner, the Yale Carbon Containment Lab, as part of a broader carbon removal announcement. That grant will support a pilot effort to bury waste biomass harvested from California forests in the Nevada desert and study how well it prevents the release of greenhouse gases that drive climate change. 

It also agreed to purchase about 415 tons of carbon dioxide eventually sequestered by the company for another $250,000, if that proof-of-concept project achieves certain benchmarks.

Whenever I've suggested "Why don't we consider just letting people bury trees," NZ climate people look at me like I'm crazy. 


A handful of research groups and startups have begun exploring the potential to lock up the carbon in wood, by burying or otherwise storing tree remains in ways that slow down decomposition.

Trees are naturally efficient at sucking down vast amounts of carbon dioxide from the air, but they release the carbon again when they die and rot on the ground. Sequestering trees underground could prevent this. If biomass burial works as well as hoped, it may provide a relatively cheap and easy way to pull down some share of the billions of tons of greenhouse gas that studies find may need to be removed to keep global temperatures in check in the coming decades. 

One of the usual objections from the kind of climate people who love to grope for excuses to ignore things that might help the climate (because those things don't force Radical Structural Change and Deep Decarbonisation) is that forests are risky because a forest that offsets emissions from a tonne of coal means a transfer of carbon from the geosphere to the biosphere, and the biosphere is risky. 

Well, carbon stored in trees can be stuck back into the geosphere. 

Look at all these approaches being tried. 

Burial costs

Other startups and research efforts are taking different approaches to the problem. 

The Australian company InterEarth believes that allowing trees to soak up salty groundwater before burying them will effectively pickle the wood, preserving it for extended periods.

The Carbon Lockdown Project, a public benefits corporation founded by University of Maryland professor Ning Zeng, has proposed creating pits that are lined with clay or other materials with low permeability.

In a paper this year, Zeng and a colleague also highlighted a number of other potential approaches, including storing biomass in frozen sites, underwater, or even in above-ground shelters. His earlier work found that harvesting and storing wood could potentially remove several billion tons of carbon dioxide a year at a cost of well below $100 a ton.

You don't need all of them to work. Or even any of these ones - there's lots of other projects being tried, including mineralisation. 

Run a clean ETS focused on net emissions and run the accounting properly. If any of these techs can scale up at low cost, we hit net zero at a low carbon price and could push for net negative, to undo the damage already done. If none of them do, we still hit net zero - just at a higher carbon cost.

I was on a panel discussion earlier this week about COP28 hosted by the NZ Institute of International Affairs - remotely, as daughter currently isolating with Covid and I don't want to impose risk on others (she's fine).  

But the whole discussion was so frustrating. 

A friend who'd attended said my presence there was felt, like a fart in Church, despite my being remote. 

I talked about the ETS, changes to help it drive to net zero durably, tech bets NZ should be making, other tech underdevelopment. 

Germany's climate rep wanted to focus on gross emission reduction. But when I asked about Germany turning off its nuclear plants and now having to rely on coal, she said nuclear is bad because of Chernobyl. I have a very difficult time taking these people seriously. Unfortunately, they set the agenda at COP.  

Anyway - burying trees isn't as crazy as it might have seemed. 

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