How to reduce ammonia emissions from agriculture

​The public consultation on the Department of Agriculture, Environment and Rural Affairs (DAERA) draft ammonia strategy ended last week, writes Richard Halleron.
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As the document points out, action on ammonia is required urgently to achieve better outcomes for nature, and for public health.

Addressing this challenge is essential to see agriculture thrive while at the same time protecting our environment.

The greater the extent and speed of action to lower ammonia emissions and reduce ammonia concentrations, the greater opportunity there will be to support sustainable farm development.

William Ervine, UFU deputy presidentWilliam Ervine, UFU deputy president
William Ervine, UFU deputy president

Northern Ireland (NI) has 394 sites of high nature conservation value designated for their protection. Almost 250 of these are sensitive to the impacts of ammonia and nitrogen. The vast majority of designated sites are currently experiencing ammonia concentrations and nitrogen deposition above the critical levels and loads at which damage to plants may occur.

As a consequence, sustained and tangible reductions in ammonia are required to protect nature, to meet Northern Ireland’s legal obligations and to ensure a sustainable agri-food sector.

Ambitious and achievable targets are required to drive the ammonia reductions required and to protect nature. The long-term target to 2050 is to reduce ammonia emissions to a point where Critical Loads of nitrogen deposition and Critical Levels of ammonia are at a more sustainable and pragmatic place.

The targets

Dairy cowsDairy cows
Dairy cows

DAERA has set two 2030 Ammonia Targets. These are: to reduce total NI agricultural ammonia emissions by at least 30% from 2020 levels. And reduce ammonia at internationally designated sites by 40% by 2020.

There are two pillars to the envisaged ammonia abatement strategy that has been proposed by DAERA. Pillar 1 comprises ambitious and verifiable ammonia reduction programme with Pillar 2 centred on conservation actions to protect and restore nature.

The establishment of a stakeholder group, representing primary agriculture, the agri-food supply chain and the environmental sector, is proposed to advise on implementation of the finally agreed measures.

The steps that can be taken on farm to reduce ammonia production and emission levels are multi-faceted.

The uptake of verifiable ammonia reduction technology in livestock housing will be encouraged. There will be a requirement to spread all slurry using low emission slurry spreading equipment by 2026.

Developing verifiable systems to encourage implementation of longer grazing seasons has significant potential for the future.

The need to reduce ammonia emissions from fertiliser will include a consultation on the potential introduction of a prohibition on the use of urea fertiliser without an inhibitor in 2024.

Establishing systems to implement and verify crude protein reductions in livestock diets can play a key role in reducing farm ammonia production levels, as will the identification and selection of genetic traits that maximise nutrient use efficiency.

In addition, supporting protein crop establishment is already available, courtesy of a pilot scheme.

And, finally steps will be taken to encourage the development and implementation of emerging technologies for ammonia reduction.

Livestock diets – reducing crude protein levels

It is universally agreed that reducing crude protein in livestock diets has a significant influence on ammonia emissions.

Reducing the amount of nitrogen (N) in animal feed reduces the amount in excreta, leading to less N being available for ammonia generation.

Scientific evidence shows that ammonia emissions are reduced by 8 -10% for every 1% fall in crude protein in pig diets.

Ammonia reductions of up to 35% are thought to be possible in poultry diets. Across the livestock sectors, including cattle, reducing crude protein in all livestock diets can achieve an industry wide reduction in ammonia of around 9%.

United Feeds has been to the fore in developing reduced protein diets for dairy cows for the past decade and more.

When the company started out on this journey the average crude protein content of a lactating dairy cow diet would have been 18% or higher. Today that figure comes in significantly lower with many diets around 16%. United’s Ruminant Product Manager Bobby Irwin points out, reducing ammonia levels within the dairy sector was not the core objective of the work initially undertaken.

He added:“Our key focus at the beginning was on finding ways of improving fertility and cow health, specifically conception rates, within dairy herds while maintaining overall milk output.

“Typically, adding protein to a cow’s diet can increase milk output. But it also encourages the animal to milk off her back. In turn, this reduces body condition score, which is a key driver of fertility.”

According to the United Feeds’ representative, reducing dietary protein will encourage a flatter milk production profile on the part of cows receiving these diets.

“Our aim was to find the ‘protein balance point’, which would allow the cow to optimise both milk output and fertility levels. There is absolutely no point in feeding cows more protein than they actually need.

“And, obviously, as feed protein levels come down, the levels of nitrogen excreted reduce accordingly and therefore overall nitrogen efficiency is improved.”

So what happens to the additional protein if the cow receives more than dietary requirement?

Bobby Irwin takes up that story:“We know that the vast bulk of the additional N is excreted as urea in the urine. Trials have shown that nitrogen excretion levels in cows’ urine can more than double if dietary protein levels are boosted from 14% to 19%.

“This process, in itself, puts an additional energy demand and increases the metabolic stress on the cow.”

The fact that urea is a very volatile chemical means that a high proportion of it is lost to the atmosphere when slurry is spread on land. Urea is also very water soluble. As a consequence, it can add to the pollution threat posed by slurry.

Typically, the nitrogen efficiency of dairy cow diets in Northern Ireland will be in the region of 22% to 32%.

The United Feeds’ representative further explained: “We have managed to significantly lower total crude protein levels within dairy cow diets without impacting at all on total milk output.

“In the first instance we can go back to the drawing board and identify which protein sources best meet the needs of the cows being fed.

“However, in overall terms we will still be taking a proportion of the protein fraction out of the diet, which can be replaced with additional energy sources and forage.

“This, in turn, gives the farmer much more flexibility in terms of securing improved cow performance whilst reducing the environmental impact.”

Protected urea

Urea is a highly concentrated chemical nitrogen fertiliser which has an NPK (nitrogen:phosphorus: potassium) ratio of 46-0-0.

Protected (or stabilised) urea is urea which is treated with an active ingredient called a urease inhibitor.

Urease is the enzyme which catalyses the conversion of urea to ammonium. It is during this conversion that ammonia gas is lost from untreated urea.

A urease inhibitor blocks the active site of the urease enzyme and this slows the rate at which urea is converted to ammonium, thus stabilising it.

According to DAERA, switching from straight urea to protected (or stabilised) urea will reduce total ammonia fertiliser emissions in Northern Ireland by 32%.

Between 7% and 53% of the nitrogen in urea fertiliser can be lost as ammonia compared with an average of 4% for Calcium Ammonium Nitrate fertiliser (CAN). However, CAN is susceptible both to nitrate leaching and to denitrification, having significantly higher nitrous oxide (a potent Greenhouse Gas) emissions than urea.

Results from a study by AFBI and Teagasc have shown considerable benefit from using urea in combination with the urease inhibitor NBPT (N-(n-butyl) thiophosphoric triamide).

Urea + NBPT offered a reduction in ammonia losses of 78.5% compared with straight urea, whilst maintaining similar agronomic yields to CAN.32 Total annual grass yields are comparable between CAN, solid urea or protected urea coated with an inhibitor. Protected urea can deliver a significant saving per unit of Nitrogen when compared to CAN.

AFBI research in 2018 found that paddocks treated with stabilised urea performed well against the paddocks treated with CAN, with similar yields at every cutting date. This confirms that comparable levels of productivity, as well as reduced volatile N losses, are achievable.

Teagasc trials have shown that CAN, urea and protected urea frequently give similar yields, but urea has the lowest N recovery. The current ammonia inventory recognises that a 70% reduction in ammonia emissions will be achieved by switching from straight urea fertiliser to protected urea.

Whilst urea use is not widespread throughout Northern Ireland and represents only 8% of all fertiliser use33, there is still potential for a notable saving in ammonia.

DAERA is working with other UK administrations to devise an approach to fertiliser which maximises benefit across environmental metrics DAERA will engage closely with the fertiliser and associated industries to identify the best way to reduce ammonia emissions from fertiliser, including examining the safe and effective use of urease inhibitors.

The UFU response

This week has seen the Ulster Farmers’ Union (UFU) confirming its official response to the ammonia draft action plan.

The organisation says it recognises the need to reduce emissions within the NI agriculture industry. However, having thoroughly read through the draft ammonia strategy and engaged with members, UFU is making it clear that the proposed policy lacks much-needed clarity and fails to deliver fair, logical proposals.

UFU deputy president William Irvine said:"DAERA's approach towards the draft ammonia strategy consultation, has been unjust from the get-go. DAERA failed to produce an up-to-date regulatory impact assessment covering all the measures proposed. It's completely unacceptable as government are unable to assess the true potential costs or benefits of these recommendations without an accurate impact assessment.

"Given the inaccuracies and gaps within the regulatory impact analysis and other parts of the draft strategy, the UFU is concerned that this consultation process is fundamentally flawed. Members have absolutely no confidence in the consultation process or the ability of DAERA and the Northern Ireland Environment Agency to draft and deliver a complex ammonia strategy that will help farmers to reduce emissions.

“The proposals are neither balanced nor coherent. The consequences will have a very significant impact on local family farms, and yet, there is limited detail on some aspects.

He added:"Members are particularly uptight regarding proposed targeted measures around internationally designated sites.

“The targeted measures focused on these specific areas has the potential to seriously hinder farming activities and affect a significant number of farmers financially. Ammonia is typically seen as a livestock problem, but all sectors will be affected with large areas of arable land being potentially caught up in the proposed policy.”

"There also remains a huge lack of clarity on a funding package and no detail is provided on how the strategy will be rolled out. While we recognise there are many technologies and techniques that could be adopted to help reduce emissions, these will range in acceptability and affordability, and the practicalities of adopting such technologies will vary between farms and sectors.”