Fertiliser use is fuelling climate-warming nitrous oxide emissions: study

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LONDON (Reuters) - The rising use of nitrogen-based fertilisers is driving up global emissions of nitrous oxide, a lesser-known greenhouse gas, complicating efforts to limit climate change, scientists reported in a study on Wednesday.

Most of the focus in curbing climate-warming gas emissions has focused on the most abundant, carbon dioxide, and one of the most potent, methane, with the fossil fuel industry under pressure to drastically curtail both.

But nitrous oxide (N20), also known as “laughing gas” or simply “nitrous,” has received less attention as a long-lasting warming agent.

“There’s much less policy attention on nitrous oxide, and not so many mitigation options, so the emissions just continue sailing on upwards,” study co-author Glen Peters, a climate scientist at the Oslo-based CICERO Center for International Climate Research, told Reuters “It makes meeting climate targets even more challenging.”

For the five-year study, published in the journal Nature, scientists at 48 institutions around the world measured and calculated both natural and human-caused N2O emissions from 1980 to 2016.

They found that N20 emissions from agriculture rose annually by 1.4% on average over those 36 years. Agriculture accounts for more than half of human-caused N20 emissions.

While nitrogen fertilisers have been crucial to boosting crop productivity and improving food security worldwide, they also can cause environmental challenges. Nitrogen in agricultural run-off can feed algae blooms that create coastal dead zones. And in the stratosphere, N2O can break down to form other molecules that destroy the ozone layer protecting the planet from ultraviolet radiation.

As a climate pollutant, N2O can linger in the atmosphere for decades, and is far more efficient than CO2 in trapping heat.

More efficient use of fertilisers could help bring down emissions, the authors wrote. They also urged efforts to curb deforestation, which can increase the amount of N20 produced by soil bacteria.

Reporting by Matthew Green; Editing by Katy Daigle and Elaine Hardcastle