Potential CO2 removal from enhanced weathering by ecosystem responses to powdered rock

Negative emission technologies underpin socioeconomic scenarios consistent with the Paris Agreement. Afforestation and bioenergy coupled with carbon dioxide (CO2) capture and storage are the main land negative emission technologies proposed, but the range of nature-based solutions is wider. Here we explore soil amendment with powdered basalt in natural ecosystems. Basalt is an abundant rock resource, which reacts with CO2 and removes it from the atmosphere. Besides, basalt improves soil fertility and thereby potentially enhances ecosystem carbon storage, rendering a global CO2 removal of basalt substantially larger than previously suggested. As this is a fully developed technology that can be co-deployed in existing land systems, it is suited for rapid upscaling. Achieving sufficiently high net CO2 removal will require upscaling of basalt mining, deploying systems in remote areas with a low carbon footprint and using energy from low-carbon sources. We argue that basalt soil amendment should be considered a prominent option when assessing land management options for mitigating climate change, but yet unknown side-effects, as well as limited data on field-scale deployment, need to be addressed first. The enhanced CO2 uptake by vegetation in response to powdered rock should be considered in assessing the feasibility of enhanced weathering as a negative emission technology in mitigating climate change, suggest simulations of a land surface model.