Enhanced rock weathering (ERW) is a carbon removal technique that accelerates the natural breakdown of volcanic rocks, such as basalt, to capture and permanently store carbon dioxide (CO2) from the atmosphere. This process involves grinding these rocks into fine particles and spreading them over large areas of agricultural land. When rainwater containing dissolved CO2 comes into contact with these particles, a chemical reaction occurs that converts the CO2 into stable carbonate minerals, effectively removing it from the atmosphere for over 10,000 years. ERW also releases essential nutrients into the soil, which benefits soil health and crop growth.
Several challenges have hindered the widespread adoption of ERW. The process requires mining, grinding and transporting large quantities of basalt which has significant energy-use and financial implications. Additionally, regulatory barriers, limited public awareness, and the need for reliable monitoring and verification have complicated its implementation. Despite these challenges, ERW does provide a unique and needed opportunity for CO2 storage and soil restoration.
Relevant research on ERW includes:
Veolia’s 2024 trial using enzymes to accelerate the weathering process.The trial involves spreading 30,000 tonnes of locally sourced basalt rock fines combined with the Carbonic Anhydrase enzyme on UK farmland. Traditional ERW takes over 30 years, but the enzyme-enhanced process only takes a couple of years. If scalable, the innovative approach could significantly contribute to global decarbonisation efforts.
A 2020 study on the impact of compost fortified with rock dust on soil properties, microbial activity, and yields at an apple orchard in China. The two-year study found that rock dust significantly enhances microelements in soil without causing phytotoxicity, boosts microbial activity and diversity, and increases apple yields and nutritional value. These findings suggest that combining rock dust with traditional composting practices can create a nutrient-rich, environmentally sustainable fertiliser that supports agricultural production.
A 2004 literature review from SEPA shows that incorporating rock-dust into composting holds promise for engaging microbial activity and nutrient retention in compost products. Studies cited within the paper (i.e. Glasgow Univeristy trials) indicate that rock dust supplementation can lead to slight increases in temperature and reductions in ammonia production during composting, suggesting benefits for odour management and nutrient conservation. The paper highlights the need for further research to optimise rock dust application for different composting systems and feedstocks and regulatory clarity to ensure rock dust-amended composts meet end-of-waste standards and environmental regulations.
In the UK, ERW, supported by rock dust-amended composts and other techniques, could remove 6 to 40 million tonnes of CO2 annually and restore our soils. The REA will update this page as research in this area continues to develop. If you have questions about ERW or need support incorporating rock dust into your composting processes, please contact us.