Intensive agriculture is responsible for a pollution "very largely underestimated"

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The first global mapping of ammonia in the air reveals new sources of emission.

By Stéphane Mandard Posted yesterday at 19h00, updated yesterday at 20h53

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Cows are waiting for milking on a farm in Escalon, California, in 2009.
Cows wait for milking on a farm in Escalon, California, in 2009. JUSTIN SULLIVAN / AFP

This is a study that could inspire a new slogan for "yellow vests": "Tax livestock, not (only) fuels! An article published Wednesday, December 5 in the very serious scientific journal Nature, shows indeed that intensive farming is at the origin of a pollution largely underestimated at the scale of the planet: ammonia.

By analyzing measurements taken by satellite between 2008 and 2016, researchers from the CNRS and the Université libre de Bruxelles have developed the first global mapping of atmospheric ammonia (NH).3). And they identified that these important sources of NH3 come mainly from intensive breeding and industrial fertilizer production.

NH3 contributes to the formation of fine particles

Ammonia is a chemical compound emitted by animal waste and nitrogen fertilizers used for crop fertilization. It plays an important role in the formation of PM 2.5 fine particles (diameter less than 2.5 micrometers), the most dangerous for health because they penetrate deep into the respiratory tract. Excess ammonia in the environment also contributes to ecosystem acidification and climate change, say the authors.

To generate this map of the distribution (to the nearest square kilometer) of the NH3 In the air, the researchers used the daily data collected for nearly ten years by an infrared atmospheric sounder developed by the National Center for Space Studies, and embedded in a satellite. They identified and categorized 248 localized sources (less than 50 kilometers in diameter) of NH3 two-thirds of which had been under radar until now. Most of these "hotspots" – households – are linked to agriculture: 83 correspond to intensive livestock farms and 130 to fertilizer factories.

A single natural focus in Tanzania

The most affected region of the world is the Ganges Valley, with NH emissions3 at 475 kilos per second. This area, which includes Pakistan and northern India, combines intensive livestock and agriculture and fertilizer production plants. At 0.81 kg / s, the mega-farms of Bakersfield and Tulare (California) and their hundreds of thousands of cows are the most important agricultural source. The most polluting industry is located in Uzbekistan, where the Ferghana Valley Fertilizer Complex, an intensive agriculture region, discharges 0.75 kg / s.