Illustration of a tractor spreading slurry, here in 2018 in Sarthe. - Gile Michel / SIPA

  • A peak in pollution was noted last week in Brittany. Fine particles are notably generated by ammonia emissions linked to agriculture.
  • In Brittany, the leading emitting region in France, agricultural authorities are working to "raise awareness" of the profession.
  • Often costly investments can reduce ammonia emissions.

There is no telework for farmers. Since the implementation of containment measures, the French peasants have not been unemployed. In Brittany, you will easily see this by observing the ballet of tractors in the fields. At the end of last week, we could also notice it by looking at the horizon of a sky clouded by fine particles. When we mentioned this air pollution on our site, some accused us of wanting to tarnish the image of agriculture. It is not so. In this period of low car traffic, the observation is clear. The application and use of fertilizers are important sources of ammonia release to the air. A factor which we know today to be decisive in the multiplication of fine particles.

Ammonia emissions to air by region according to an Ineris study. - Airbreizh

The situation is also well known to agricultural authorities. The latter know that they are at the forefront of the French State's commitment to lower its ammonia emissions in the air by 13% by 2030. A commitment which will lead to significant sanctions by the Europe if it was not respected. “This is a very emerging question. We are trying to push it but we are in an awareness ”, recognizes Charlotte Quénard, environmental advisor at the Brittany Chamber of Agriculture.

Spring, a critical period in the fields

The first French agricultural region is not surprisingly the first emitter of ammonia in the air. “In the background, there are the emissions from the livestock buildings. But it is the spreading work that increases air emissions, especially in the spring, ”says Gaël Lefeuvre, director of Airbreizh.

Its air quality monitoring association issued an alert last week, citing "poor" air quality throughout Brittany. Or a few days after submitting its first report on the monitoring of ammonia in ambient air. A document that enabled Airbreizh to invest in a first measuring device estimated at 70,000 euros which will soon be installed in its Kergoff station in central Brittany.

Nitrogen escapes into the water… And into the air

The problem of ammonia in the air is quite simple to understand. To enrich their soils, farmers deposit liquid manure, rich in nitrogen, in order to feed the plants. But part of this nitrogen escapes into the water, a determining factor in the arrival of green algae. Another part evaporates into the air, generating ammonia. To deal with this, solutions have been established and compiled in the "Guide to good agricultural practices for improving air quality". “It is above all a collection of techniques intended for agricultural advisers. Because the farmers have a global vision of their exploitation, they are not going to take such or such measure to improve a point or the other, explains Charlotte Quénard.

In pig or poultry farms, air washers are mandatory for the most significant installations. But the nerve of the problem is above all economic. “The most used fertilizer was ammonitrate. But we see more and more farmers taking urea because it is much cheaper. The problem is that it generates three times more ammonia emissions, ”continues the environmental adviser.

One solution would be to invest in more modern spreading equipment. A “boom ramp” allows the slurry to be buried and to avoid its dispersion in the air. But the additional cost is estimated at 2,500 or even 3,000 euros per meter of spreading. Imagine when the ramp is 15 meters wide. “The public authorities must help finance the equipment. It's like cars or boilers, if you want to encourage people to change them, you have to help them, ”concludes Charlotte Quénard. The famous "awareness".

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New diesel and ammonia

In Brittany, 97% of ammonia released into the air is attributed to agriculture, according to a report by Ineris. But another source could prevail. Scientists say the new ADBlue-type diesel engines are expected to reduce nitrogen oxides. However, the presence of urea in the composition would promote ammonia emissions.

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