Burying trees to save the climate

It would be a strange geoengineering technique which would consist of burying trees (dead, of course), to sequester carbon. Some current projects are part of the great bric-a-brac of geoengineering.

Vincent Nouyrigat, editor-in-chief of the magazineEpsiloon tells us today about a unique proposal from scientists who propose a new method of CO2 sequestration. A The discovery of a tree buried in clay around 3,800 years ago, which the authors analyzed, shows that it has deteriorated very little during this period.

franceinfo: This new method for trapping CO2 seems a little strange: is it really about burying dead trees?

Vincent Nouyrigat: It’s true that the idea may seem a little far-fetched, but it is ardently defended by very serious researchers at the University of Maryland. We talk a lot about reforestation and open-air forests. It’s very good to capture CO2, but you still need to be able to store it for a long time.

The problem is that the numerous dead trees, but also trunks and branches resulting from clearing or forestry activity, decompose over time: insects, fungi and other micro-organisms devour the wood, and release carbon in the atmosphere. This is precisely what these researchers want to avoid.

The idea for the burial came to them when they discovered the trunk of a red cedar in soil in the province of Quebec, two meters deep. A cedar whose analyzes have shown that it has been buried in this place for more than 3700 years! And the most astonishing thing is that this tree is almost intact: It lost very little carbon, barely 5%, because it was immersed in very compact clay soil blocking the arrival of oxygen and therefore its decomposition.

So it would be enough to imitate, reproduce this natural phenomenon?

Exactly, it would be as simple as that: dig a pit – or exploit an abandoned mine or quarry near a forest – dump loads of wood into it, and cover everything with clay, for at least a millennium . No need for special machines or sophisticated techniques.

These researchers estimate that this solution could sequester up to 10 billion tonnes of CO2 per year, or around a quarter of our current emissions; all at a lower cost, they say (around $30 per ton). A handful of startups have already started fundraising, and the first small experiments are taking place in North America.

So a solution to put in place as quickly as possible?

We really have to be very careful about these kinds of promises. The concept is rudimentary and clever, but we are waiting to see the results of real experiments, and the study of possible undesirable effects; removing dead trees could undoubtedly disrupt the natural cycles of forests.

More generally, this solution is part of a large jumble of geoengineering proposals being put forward at the moment. It all looks a bit like tinkering with uncertain effects: some want to refreeze the ice caps, others create huge plantations of macro-algae in the middle of the oceans, or even scatter crushed basalt in the fields.

This is reassuring, humans do not lack creativity in trying to urgently extract CO2 from the atmosphere. But all climatologists are clear: this tremendous inventiveness should rather be put at the service of our sobriety.