A study has found that spreading powdered basalt rocks over farmland could decrease nitrous oxide (N₂O) emissions. Specifically, this would bring climate change benefits without affecting the protective ozone layer in the upper atmosphere. 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 negatively 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.

This computer model simulated the effects of reducing N₂O emissions over 50 years from 2025 to 2075, incorporating interactions between the 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. Contributing to the study was Dr James Keeble from the Lancaster Environment Centre.

An additional benefit emerging from the research was the combination of reduced N₂O emissions and carbon dioxide removal by the crushed rock. This could provide a cooling effect on the climate by 2075. It represents a modest but meaningful contribution to climate change mitigation efforts. The results of the study, 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 from University of Reading and Dr Maria Val Martin from Sheffield University with contributions from Professor David Beerling at Sheffield University and Dr Luke Abraham from University of Cambridge in addition to Dr James Keeble.

On the outcomes of the study, Dr Keeble said: “When we consider approaches to tackle climate change, we must also explore the potential impacts on stratospheric ozone. Our study suggests that enhanced rock weathering techniques should pose no threat to ozone recovery. As we consider other approaches to tackle greenhouse gas emissions, we must always be cognisant of the need to ensure the continued success of the Montreal Protocol and the recovery of the ozone layer.”