Soils could help combat climate change

A team from Newcastle University in Britain aims to design soils that can remove carbon from the atmosphere — permanently and cost effectively.

The researchers believe this has never previously been attempted anywhere in the world.

The concept underlying the initiative exploits the fact that plants, crops and trees naturally absorb atmospheric CO₂ during photosynthesis and then pump surplus carbon through their roots into the earth around them.

In most soils, much of this carbon can escape to the atmosphere or enters groundwater. But in soils containing calcium-bearing silicates (natural or man-made), the team believes the carbon that oozes out of a plant's roots may react with the calcium to form the harmless mineral calcium carbonate. The most common natural forms of calcium carbonate are chalk, limestone and marble.

The carbon then stays securely locked in the calcium carbonate that simply remains in the soil, close to the plant's roots, in the form of a coating on pebbles or as grains.

The scientists are investigating whether this process occurs, for it may encourage the growing of more plants, crops and so on in places where calcium-rich soils already exist. It would also open the prospect that tailor-made soils can be designed (with added calcium silicates or specific plants) that optimise the carbon-capture process.

Such soils could play a valuable role in carbon abatement all over the globe. The team members will first try to detect calcium carbonate in natural soils that have developed on top of calcium-rich rocks or been exposed to concrete dust (that contains man-made calcium silicates).

They will then study artificial soils made at the university from a mixture of compost and calcium-rich rock. Finally, they will grow plants in purpose-made soils containing a high level of calcium silicates and then monitor accumulation of calcium carbonate there.

The multi-disciplinary research team, including civil engineers, geologists, biologists and soil scientists, is led by David Manning, Prof of soil science at Newcastle University, north-east England.

The research is being funded by the Engineering & Physical Sciences Research Council.