How to solve the 245kt/yr problem of ammonia emissions?

Agriculture emitted 244,900 tonnes of ammonia in 2017, up 10% since 2017, according to the official estimate. As DEFRA prepares to introduce tougher regulations to tackle the problem, experts say this will be far from straightforward

In April 2018, Jamie Butler hosted DEFRA’s air-quality team at his farm in the south-east. He swotted up on methane emissions and climate change, only to be told the event would focus on ammonia. “I had no idea it was high on the [government’s] agenda to reduce ammonia emissions, and I certainly had no idea scientists are pointing at the dairy industry as one of the biggest offenders,” he wrote in a blog for the National Farmers Union (NFU).

He was not the only one lulled into a false sense of security. Having met its EU National Emissions Ceiling Directive target for 2010 – a 7.5% ammonia reduction against a 2005 baseline, there was a feeling the UK would coast through the 2020 one – an 8% drop from 2005. But then milk quotas ended and cow numbers jumped, as did reliance on imports of cheap, urea-based fertiliser.

The latest inventory report showed UK agricultural ammonia emissions were up 3.7% in 2017 on 2005 figures. “It was a wake-up call,” says professor Mark Sutton from the Centre for Ecology and Hydrology. “Now we have to do something about it.” 

The government’s clean air strategy, published in January, turned attention towards ammonia, and on agriculture. The sector accounts for 87% of ammonia emissions in the UK, with almost half (47%) coming from cattle.  

DEFRA promised a policy requiring farmers to incorporate all solid manure to bare land within 12 hours “in the shortest possible timeframe”. “Lots of ammonia is lost in the first six hours, so the sooner [ it is incorporated] the better,” says professor Tom Misselbrook, who leads research on soil and atmosphere interactions at Rothamsted Research. 

Other proposals have long lead times, which has surprised some. Slurries and digestate must be spread to land using low-emission spreading equipment, such as trailing shoe or injection rather than a splash plate, by 2025.  

The UK now looks likely to miss its 2020 “ceiling” and could face fines. David Ball, environment and buildings senior manager at the Agriculture and Horticulture Development Board, admits farming has “slipped through the net”, but regulation is now “coming at us in what appears to be a short timeframe”.

The new measures – which also include “mandatory house designs for new intensive poultry, pig and beef livestock units and dairy housing” – could help reduce ammonia emissions. DEFRA forecasts published in April predict the 2030 ceiling (16% cut) will be met, provided the clean air strategy is successfully implemented. But that’s a big “if”.

DEFRA estimates that meeting the 2030 targets will cost £73m a year by 2030. Potential societal savings dwarf that, but this offers little comfort to farmers. “Dairy isn’t a profitable sector... and we hope DEFRA takes that into consideration,” says NFU environment adviser Grace Whitlow. 

The Environment Agency has been tasked with developing an environmental permitting regime for cattle farms, something the sector is concerned could be particularly burdensome. 

The first step will be to agree the “best available technique” documents for limiting pollution from the farms, encompassing ammonia as well as water and methane, whose levels can rise following some ammonia mitigation. Whitlow says costs could be cut if the regime is “more flexible” than the one in place for intensive rearing of poultry and pigs. 

DEFRA has not yet defined “intensive” in relation to beef units. References to “dairy”, meanwhile, are not prefixed with “intensive”, leaving the door open to include all kinds of farms. This could be a recipe for disaster, warns the Royal Association of British Dairy Farmers. “While environmental permits work for the pig and poultry sectors, the dairy industry is less intensive and does not fall into defined production systems such as ‘all continuously housed’,” its response to the strategy said.

Monitoring emissions from the farms, let alone setting thresholds, will be tricky. Still, with more animals reportedly spending less or no time grazing, and with the number of so-called mega-dairies and intensive beef farms, which keep hundreds of animals housed for most of the year, on the rise, the environmental burden from slurry is growing. 

One option could be a tiered system, with a light-touch approach for medium-sized farms and a full, integrated pollution-control regime for the largest. Ball does not expect to see a permit requirement for small extensive dairy farms. The sector would have preferred a voluntary approach, but uptake of ammonia-emission mitigation has been “relatively small”, adds Misselbrook. “We needed some kind of push from government.” The big question now is: whom to push and how hard?

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