Burying wood - A solution to Nature-Based Additionality problems?

Header Image: Intact wood from an 8000 year old neolithic dock. The wood and carbon remains intact because the dock was buried by a tsunami and lay in anaerobic conditions, preventing decay. Source: Britain’s Channel 4 Public Broadcasting Corporation.

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The concept behind Carbon Burial is extremely simple: grow trees on old agricultural land, cut them down, bury the wood in an anaerobic environment, and then repeat the process. The greatest benefit of this approach is that it’s an efficient, additional, and permanent way of removing carbon from the atmosphere.

Many existing ‘reforestation’ carbon projects are simply timber plantations that harvest the trees and use the wood for timber or paper. They remove some carbon just by being there, but their wood/carbon ultimately gets broken down and emitted back into the atmosphere, making their value as carbon projects questionable. Take Guanare for example, a Verra reforestation project that Renoster rates a zero. These trees are being planted by a multinational timber company for paper production, they’re clearcut and replanted every 15 years, and once the project is complete the owner may simply walk away with no long-term carbon benefit at all.

Carbon burial is different. Trees are being grown exclusively for carbon removal, and all of their wood will be used purely for carbon offsets. Trees are gigantic carbon vacuums, and if used to their maximum potential they can remove more than 15 tonnes of CO2 per hectare per year. That means that with this approach, a medium-sized tree farm of about 250 hectares can outdo the world’s largest direct air capture facility annually.

Of course, the key to making this work is burying the wood in an oxygen-free environment where it can’t decay and release carbon back into the atmosphere. That may mean burying the wood in clay or below the water table. Wood could even be placed in old mine shafts, and there’s something romantic about filling up 20th-century coal mines with carbon – essentially replacing what we removed.

The natural drawback to this approach is that industrial tree plantations don’t offer many ecological co-benefits. Renoster doesn’t want to see the whole world covered in Eucalyptus plantations. Some trees are usually better for the environment than no trees, but this approach will never offer the benefits of a native forest that’s simply left alone. That’s why Renoster’s team of scientists stress that carbon burial should be combined with other project types like natural regeneration and conservation.

Ultimately though, carbon burial offers a way out of many of the criticisms that nature-based carbon offsets face. The carbon will remain removed for as long as the wood remains buried (presumably forever). There is no doubting the intentions or the additionality of trees planted for this purpose. And there is very little opportunity to manipulate baselines and carbon numbers as we see in other project types. Essentially, this approach uses nature to its maximum potential to get us out of this mess.