Sprinkle rocks on farms to cut emissions and aid ozone layer

Spreading powdered basalt over farmland could decrease nitrous oxide (N2O) emissions, providing a climate change benefit without affecting the protective ozone layer in the upper atmosphere, a study has found.  

N2O is a potent greenhouse gas that contributes to the warming of the planet. N2O emissions are rising, primarily due to human activities including fertiliser use. N2O can also affect the ozone layer, meaning any strategy aimed at reducing N2O emissions must also consider the impact on the ozone layer. Using a state-of-the-art computer model, scientists simulated the effects of reducing agricultural N2O emissions over the next 50 years.  

The study examined two main approaches to reduce N2O emissions: spreading crushed basalt rock on fields and using special chemicals (nitrification inhibitors) which reduce N2O production. The results, published in June in npj climate and atmospheric science, indicate that these methods could lower N2O emissions from agricultural sources.  

The study was led by Dr James Weber (formerly at Sheffield, now University of Reading) and Dr Maria Val Martin (Sheffield) with contributions from Professor David Beerling (Sheffield), Dr James Keeble (Lancaster) and Dr Luke Abraham (Cambridge). 

Dr James Weber said: “Reducing nitrous oxide emissions by spreading crushed basalt and nitrification inhibitors on farmland is unlikely to harm the ozone layer, which is still recovering from previous damage. 

“The findings show the potential for feasible agricultural practices implemented globally to contribute to climate action with a low risk of unintended consequences for the stratospheric ozone recovery.” 

Protecting the ozone layer

Scientists employed a state-of-the-art computer model to simulate the effects of reducing N2O emissions over 50 years from 2025 to 2075. This model incorporates interactions between the atmosphere, land, ocean, and atmosphere. The researchers examined two contrasting future climate scenarios - a future with significant global surface warming, and a low surface warming future. Within these simulations, the scientists explored two agricultural methods to reduce N2O emissions: adding crushed basalt to croplands and using nitrification inhibitors on agricultural soils.  

The simulations showed that these methods could reduce global N2O emissions by 5% compared to present-day levels. This reduction in N2O does not hinder the ongoing recovery of the ozone layer and even led to slight increases in ozone concentrations in some mid-latitude regions.  

An additional benefit emerged from the research. The combination of reduced N2O emissions and carbon dioxide removal by the crushed rock could provide a cooling effect on the climate by 2075. This represents a modest but meaningful contribution to climate change mitigation efforts. 

Weber, J., Keeble, J., Abraham, N.L. et al. Global agricultural N2O emission reduction strategies deliver climate benefits with minimal impact on stratospheric O3 recovery. npj Clim Atmos Sci 7, 121 (2024). https://doi.org/10.1038/s41612-024-00678-2