Removing carbon from the atmosphere

Weathering happens when the CO₂ in rainwater reacts with rocks and soil minerals in the ground, converting it into non-harmful forms of carbon such as hydrogen carbonate ions.

These then run off into rivers, groundwater and the ocean where they can be stored securely for hundreds of thousands of years.

Using her background in weathering and geochemical techniques, Rachael is leading work with a mining company to apply their waste products to agricultural crops and quantify how much CO₂ can be captured. They then compare these results to sites where this treatment isn’t being used.

The field trials are being carried out in the UK, Brazil, Malaysia and the US.

Carbon capture is not the only advantage of enhanced rock weathering. The nutrients in the rocks act like fertilisers and increase the yield of the crops. In equatorial regions where dietary zinc deficiency is common, the high level of zinc in the rocks increases the amount of zinc in plants and subsequently in people’s diets.

The research has seen a huge amount of international interest from a wide range of organisations including:

• mining companies who want to find a use for their waste materials
• farmers who want to use the crushed rock as a fertiliser to increase their yield and reduce their lime use
• start-up companies and entrepreneurs who want to market the process to large companies looking to reduce their carbon footprint

However, Rachael warns there may be limits to the extent of the technology as the process is dependent on a supply of reactive rock dust. But despite this, the potential future impact of implementing this technique is looking positive. 

Rachael said: “The calculations and field trials we have done indicate that introducing enhanced rock weathering could contribute to an upper limit of 10 percent of the amount of CO₂ that needs to be absorbed from the atmosphere to meet the Paris agreement target for carbon dioxide removal.”