Using a combination of crushed rock and fertilizer can decrease nitrous oxide emissions on farms

Spreading crushed basalt on farmland and using special fertilisers to prevent nitrogen loss could cut global agricultural emissions of gases that are a powerful driver of global warming by 25%.

Nitrous oxide is a greenhouse gas with a warming potential 270 times greater than carbon dioxide. It has increased by 40% in the past 40 yearsAgriculture is a major factor, due to increased use of nitrogen-based fertilisers and rising livestock numbers.

Microorganisms in the soil convert ammonium in manure and animal waste into nitrates, releasing nitrous oxide in the process. Compounds that interfere with this process are called nitrification inhibitors, and can be added to fertilizer to reduce nitrous oxide emissions. Applying basalt dust to the soil, a technique called enhanced rock weathering (ERW), can also help by making the soil more alkaline.

However, nitrous oxide emissions are not only a global warming pollutant, they also have a complex relationship with the ozone layer, and in some circumstances even help it recover, so figuring out the best way to mitigate nitrous oxide emissions without damaging the ozone layer is difficult.

To address this, Maria Val Martin Researchers from the University of Sheffield in the UK modelled the impacts of widespread use of both ERW and nitrification inhibitors on nitrous oxide emissions and the ozone layer under two different climate scenarios.

The researchers found that a “moderate” approach, in which ERWs were introduced in key regions around the world and most farmers except the poorest used nitrification inhibitors, could reduce nitrous oxide emissions from agriculture by 25 percent, while nitrous oxide emissions overall would be reduced by 5 percent. These gases also come from combustion engines and industry.

What's more, up to two gigatons of additional carbon could be sequestered in the soil thanks to ERW, and neither scenario would harm the ozone layer, Val Martin says.

“we [carbon] “Enhanced rock weathering would sequestrate carbon dioxide, reduce nitrous oxide emissions, which is 300 times more potent than carbon dioxide, resulting in climate benefits, and protection of the ozone layer,” she says.

Deploying nitrous oxide abatement efforts on this scale would cost billions of dollars. Sequestering carbon using ERW costs between $80 and $180 per tonne of CO2. According to previous researchAccording to Val Martin, reducing nitrous oxide emissions is a “free” side benefit of carbon sequestration. Applying nitrification inhibitors costs about $28-45 per hectare, which would cost $17-27 billion per year to cover the 600 million hectares modelled in the study – roughly one-eighth of all agricultural land.

Still, Val Martin says the scenario is deliberately cautiously ambitious, and one that could play out in the real world. “What we wanted to do in this study is to come up with a realistic scenario, so if governments want to curb nitrous oxide emissions, [these] It’s a strategy we’re implementing.”

Parbhu Suntaralingam Researchers from the University of East Anglia in the UK say new strategies to curb nitrous oxide emissions are urgently needed, and that this research is particularly valuable because it focuses on curbing emissions without damaging the ozone layer.