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The hidden polluters

Stijn Strake/Unsplash

Next to clean enough air, food is one of humans’ most basic needs. But the way it’s produced could be making it harder for us to breathe.

Towns and cities are often the assumed battlegrounds in the fight against air pollution, but there is another, perhaps more contentious, location: agriculture.

Research has found that cutting farming emissions by half could save more than 200,000 lives across 59 countries of the world.

According to the Food and Agricultural Organization, greenhouse-gas emissions from agriculture, forestry and fisheries have more than doubled over the past 50 years. Without greater efforts to reduce them, there could be an additional 30-per-cent increase by 2050.

Pollution from agriculture can also contribute to ground-level ozone, which can have a negative impact on crops. One estimate, looking at the impact on soybean, wheat, rice and maize production in several countries, estimated that yields could be reduced by up to 227 million tonnes a year. ‘If you’re in a part of the world where food is already scarce, that’s a really big effect,’ says Alastair Lewis, a professor at the National Centre for Atmospheric Science, England.

But of all of the pollutants, it’s ammonia where agriculture dominates. Farming accounts for 92 per cent of total ammonia emissions across 33 European countries and since 2014 emissions have been on the rise.

Nitrogen-based ammonia gas is emitted from fertilizer and the breakdown of urea in animal manures and slurries. It combines with other pollutants, mostly from vehicles and industry, to contribute to penetrative particulate matter in the air. In fact, one study found that, in much of the US, Europe, Russia and China, emissions from farms outweigh all other human sources of fine particulate matter.

Agricultural air pollution is not just an issue for rural areas. ‘A very significant fraction of the particles that people breathe in cities will contain ammonia. Part of that will have originated from farms outside, possibly hundreds of thousands of kilometres away,’ says Lewis.

Nitrogen is a critical natural fertilizer. It can also be added to crops to boost productivity, but the natural nitrogen cycle is upset when it’s overloaded and the nitrogen reacts with other things in the air. When nitrogen ‘leaks’ out of the cycle natural habitats can become ‘over fertilized’, upsetting delicate ecosystems and increasing soil acidity.

Change isn’t easy

Lewis says that agricultural air pollution is a hard battle to wage politically. ‘Speaking frankly, people do not like to impose things on farmers, they’re some of the most difficult people to introduce policy with, particularly in Europe.’

There are various ways to reduce ammonia emissions on farms: These include using less fertilizer, covering and storing slurry correctly, and spreading manure in ways that reduce emissions, such as injection, but many of these come at a cost for farmers.

Lack of time and infrastructure also gets in the way, particularly when farmers trying to produce cheap food already have such squeezed profit margins. In the UK, where campaigns from dairy farmers against falling milk prices have resulted in blockades and protests, the dairy and beef sector accounts for 40 per cent of the ammonia released into the atmosphere.

Ian Ludgate is an environment adviser at the National Farmers Union in Britain and says that farmers are already doing a lot. ‘Clearly, ammonia emissions are primarily an issue for agriculture, but, there’s probably only so much that farmers can do within realistic cost requirements and practicality.’

He points out that reduction of ammonia emissions also benefits farmers, in terms of reducing losses. ‘Essentially you’re losing nitrogen that could otherwise be feeding the crop or the soil. It’s within the farmers’ interests to reduce this too.’

Turning the tide?

Some European countries are starting to get a handle on the problem: Denmark reduced ammonia emissions by 40 per cent between 1990 and 2016, through stronger regulations on manure spreading and slurry storage, as well as financial help for farmers. In the Netherlands, similar measures were introduced that reduced ammonia emissions by 64 per cent over the same period.

Despite this, the Netherlands still has big problems: In 2019, the country’s Prime Minister Mark Rutte described the pollution issue as the most difficult he had faced in his time as leader, because of its complexity. The country’s stikstofcrisis (nitrogen crisis) caused applications for tens of thousands of farming and construction permits to be halted as the Dutch government tried to comply with a court order to cut nitrogen pollution and stop violation of European Union pollution laws and protect nature. Hundreds of farmers came out in protest and blocked motorways.

To make a real dent in agriculture’s emissions, we also need to think about what we farm – not just how. The Centre for Ecology & Hydrology published a report in 2014 which explored how much Europe’s food choices affect nitrogen emissions, climate change and land use. The researchers found that the nitrogen footprint of the average diet would be reduced by 40 per cent if people took a ‘demitarian’ approach and halved the amount of meat and dairy they ate, due to the relatively low nitrogen ‘losses’ of plant-based foods like cereals.

Mark Sutton, an Environmental Physicist and one of the report’s authors, says he’s feeling optimistic: ‘This has been a topic where not much has been happening for 20 years and now we’re really seeing countries beginning to buy in at the highest level. We need to start grasping this.’

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