Any relevant arguments or ideas on ways to reduce ammonia in NI will be welcomed as part of the DAERA consultation on a draft ammonia strategy, which closes on 3 March 2023.

At the second of three public events taking place at CAFRE colleges, DAERA officials at Enniskillen campus emphasised that no final decisions have been taken. Ultimately, it will be up to a future minister to determine what rules and regulations are put in place to reduce ammonia emissions from farms.

One of the main concerns raised was the cost for smaller farmers to comply with a proposed ban on slurry spreading with splash plates from 2026.

In addition, farmers argued that with their own equipment, they can spread when conditions are ideal, but if they are forced to rely on a contractor they will be at the back of the queue and potentially end up applying slurry in marginal weather.

“It is a proposal. If you have any caveats, it is important that is fed into the consultation process,” responded Dr Kate Semple from DAERA.


The use of low emission slurry spreading equipment (LESSE) is one of five relatively low-cost measures initially analysed by economists at the Agri-Food and Biosciences Institute (AFBI), which combined have the potential to reduce ammonia emissions by up to 21%. Annual cost to the industry was estimated to be £6.63m.

However, with ammonia emissions in NI gradually rising since 2010 on the back of dairy expansion, this 21% reduction is unlikely to be enough for NI to contribute its fair share to international obligations signed up to by the UK.

The UK target is a 16% cut in emissions by 2030, based on 2005 figures. In 2020, NI ammonia emissions were up 5% when compared to 2005. The DAERA consultation proposes a 2030 target to cut emissions by 30% when compared to 2020 levels.

Achieving that will require additional – and much higher – cost measures beyond the five initially assessed by AFBI (LESSE, lower crude protein in livestock diets, longer grazing seasons, use of protected urea and livestock genetic improvement). As part of their analysis, AFBI economists suggested that a 25% reduction in ammonia will cost industry over £30m annually.

In its consultation, DAERA lists other actions such as low emission livestock housing, emerging technologies such as the acidification of slurry, establishing trees around livestock housing and covering above ground slurry stores.

In terms of future funding to incentivise change on farms, Dr Semple said there is the potential that DAERA could draw down money from the Stormont Executive’s Green Growth strategy. She also expects new programmes to come forward similar to Tier 1 of the Farm Business Improvement Programme, to help fund the uptake of LESSE on farms.

Trailing shoe out-performs dribble bar

Previous research has shown that when slurry is spread using a dribble bar, ammonia emissions are 30% lower than when a traditional splash plate is used.

However, the reduction in emissions rises to 60% with a trailing shoe system and is 70% lower if a slurry injection system is fitted to a tanker.

“Shallow injection is not particularly suitable on the drumlin hills of NI or on stony ground I’m afraid,” commented CAFRE adviser Gary Haslem at the event in Enniskillen. Given the figures quoted, he was asked whether DAERA might, in future, insist that a trailing shoe is used.

“There is no policy line on it, but you can see the direction we want to go. If I had to write the cheque, I would probably go for the trailing shoe,” responded Haslem.


On the other “low-cost” options to reduce ammonia emissions, he pointed out that 61% of ammonia comes from the management and spreading of slurry, while just 7% comes from grazing livestock. “You can see why we want more cattle outside,” he said.

The DAERA consultation also proposes a ban on the use of straight urea. When urea is converted to ammonium post-spreading, ammonia gas is lost. Treating urea with a urease inhibitor will reduce emissions and will have no detriment to yields, advised Haslem.

When it comes to the proposal to reduce crude protein in livestock diets, he said the target is to give an animal what it needs, rather than excess. If too much crude protein is fed, it results in higher excretion rates of nitrogen and ultimately ammonia. The advice from scientists is that significant reductions in ammonia can be achieved by more precise livestock nutrition.

The final low-cost option is to improve feed efficiency by breeding from the best genetics. Cattle that are more efficient at converting feed into beef or milk will excrete less nitrogen per kg of output.

New technologies within livestock housing

If NI is to achieve a 30% reduction in ammonia emissions by 2030, significant investment will have to be made in new technologies within livestock housing.

Ammonia is released when urine and faeces mix on the floor of a shed, so the aim of various technologies is to stop mixing from happening or to get the urine and faeces rapidly into a tank.

“There isn’t one solution that fits all. Flooring systems on the ruminant side is a main focus,” said Gary Haslem.

On some farms, more regular scraping of solid floors will significantly cut emissions, while comfort slat mats or grooved slats both help get urine more quickly into underground storage.

Acidification systems, whether fitted in a shed, or in-field when spreading, could also have a role, said Haslem, who explained that by lowering the pH of slurry you lower the ability to release ammonia.

Slurry stores

Under the current nutrients action programme, all new slurry stores must be fitted with a cover, but preliminary analysis suggests 80% of existing above ground stores in NI are not covered.

Research suggests that covering all stores would reduce ammonia emissions from manure storage by 16% and overall agricultural emissions by 1.3%.

According to Haslem, there are a number of options. A fixed tensioned cover delivers the highest ammonia reduction (80%), followed by a floating plastic cover, floating plastic tiles or floating expanded clay balls (all 60%). Simply allowing a crust to form on top of the tank reduces ammonia emissions by 40%.


The final potential measure is to plant trees around livestock housing to capture ammonia emissions. According to the information presented by DAERA, a well-designed plantation can capture up to 25% of emissions from a livestock house. However, “a row or two of trees will have little effect”.

Lely system to cut ammonia

As an example of one of the technologies on the market to reduce emissions from livestock housing, Dr Kate Semple quoted a Lely Sphere system she viewed on a visit to the Netherlands in 2022.

It includes a flooring system that allows only urine to get into the below-ground tank. Faeces on the floor is collected by a robot and dumped into a separate pit. Outside the house, a ventilation unit creates a negative pressure in the underfloor tank, so any gases in the house are sucked in. This air passes through a filter, capturing ammonia with acidified water, which can be spread on land.

“It was very impressive. But it will cost around £250,000 plus running costs,” said Dr Semple.


She also outlined that there is an ongoing programme of work locally at AFBI to assess different additives and treatments for slurry. “There is a house being built at AFBI to determine their effectiveness,” she said.

Ammonia impact on peatland

Measurement of ammonia concentrations at eight special areas of conservation (SAC) across NI shows that six of these sites have ammonia above a critical level at which ecological damage is likely to occur.

“The damage to peatlands is extremely visible. We see dead sphagnum on peatland across NI,” Keith Finegan from the NI Environment Agency told the meeting in Enniskillen.

He said that ammonia normally peaks in February/March and again in September/October to coincide with the opening and closing of the slurry spreading season.

Restoring peatland by blocking drains etc is seen as being crucial to NI getting to net zero greenhouse gas emissions by 2050, as healthy sphagnum is able to capture carbon from the atmosphere. Against that backdrop, a peatland strategy is currently being taken forward by DAERA, with plans to bring 150,000ha of peat soils under “sustainable management”.

To measure whether a particular site is sequestering or releasing carbon, an eddy covariance tower can be used. This equipment has now been installed at four sites across NI to include three lowland raised bogs, with the fourth at Greenmount hill farm in Glenwherry.

“The lowland raised bogs surrounded by agricultural activity are under more pressure and aren’t performing as well. The plants aren’t as healthy and are not as productive as Glenwherry. There is sequestration in the summer, but it is not as good as it could/should be,” said Finegan.

“The peatland strategy cannot be addressed if we do not tackle ammonia,” he added.

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