Ammonia emissions – What next for the pig industry?

Zanita Markham explains how a collaborative approach has led the Environment Agency to update their ammonia emission factors to bring the standard figures in line with modern livestock rearing practices, saving the pig industry over £15m.

In November 2024, we announced that new ammonia emission factors (EF) for Environmental Permitting Regulations (EPR) were being published on the Government’s website.

It was a milestone for the pig industry, demonstrating how seriously it takes its responsibilities for environmental improvements and how important data gathering is – not forgetting that it also saved British pig farmers an estimated £15.3m in environmental mitigation costs.

The announcement was also a recognition of the collaborative approach between the pig industry, levy payer investment in AHDB and government agencies. It has led the Environment Agency (EA) to update its ammonia EF to bring the standard figures in line with modern livestock-rearing practices, nutrition and genetics.

Emission factors

For permitted pig and poultry farms, these EF are used for Pollution Inventory reporting and during the permitting process to quantify and assess the impact of emissions on nearby protected nature sites. They also demonstrate compliance with benchmark levels known as best available technique associated emission levels (BAT AELs).

These changes have been informed by our multi-year monitoring project and the EA-commissioned ADAS and Rothamsted Research data review of ammonia emission factors for permitted pig and poultry operations in the UK.

Table 1. New standard emission factors for pigs 7–30 kg (kg NH₃/animal place/year) 

Table 2. New standard emission factors for pigs over 30 kg (kg NH₃/animal place/year)

Table 3. New standard emission factors for farrowing units (kg NH₃/animal place/year)

Table 4. New standard emission factors for dry sows, including gilts (kg NH₃/animal place/year)

What do farms do now?

A reduction has been seen for all pig housing systems – this is where the predicted spend of around £15m has been saved in estimated alterations and installations of abatement technologies.

Even though there has been a reduction across the board, it wasn’t large enough to see total compliance across all housing systems. There are two systems that remain non-compliant with the BAT AELs: pigs over 30 kg and dry sows, both on fully slatted floor systems. These systems need an 8% and 9% reduction in ammonia emissions, respectively.

But this is where I aim to offer some reassurance that there are quick wins that can be actioned on farm to become compliant.

Scenarios accepted as standard

Regular removal of slurry (either by scraping, flushing or pumping) for both non-compliant housing systems will straight away place you in a compliant system. There is now an agreed definition of ‘frequent’ slurry removal, which is at least weekly. The implementation of this slurry management system can see a reduction in ammonia emissions of 25%.

Reducing the crude protein in feed is recognised to lower ammonia emissions. Where a farm is feeding a reduced crude protein diet, reductions in ammonia emissions can be seen. The EA will accept a reduction in EF of 10% for every 1% reduction in dietary crude protein, up to a maximum EF reduction of 20%. This will need to be evidenced as part of any permit application.

Other available options:

• Retaining the last wash water in the pit: When slurry is collected in the water that is kept in the pit after cleaning or refilled until a depth of 120–150 mm, a dilution effect is most beneficial
• Phase feeding: The addition of amino acids can reduce ammonia emissions by up to 19%
• Polyethylene floating balls in slurry channels
• Slurry acidification, which can reduce ammonia emissions by up to 75%

Emission factors are the most preferred option of reporting on an industry average. Applicants or permit holders are also able to self-evidence a site-specific factor if they believe their emissions are lower, although this can be costly.

There is also the potential for an alternative approach using nitrogen excretion data to generate farm-specific EF based on specific nutrition and animal performance parameters.

Current permit holders might notice there is a reduction in housing systems listed against EFs due to better standardisation, taking forward the most practical scenarios, with some previously listed systems now becoming redundant.

For new applicants who do not wish to use the standard EFs, bespoke EFs can be suggested. If your proposed system or management technique is not listed as one of the accepted scenarios, a case-by-case approach is taken. It is likely that robust evidence will be required to support proposed reduced EFs as part of permit applications.

Our focus for the future

With it being 20 years since the last large-scale study of ammonia emissions, there is recognition that more frequent monitoring could be both beneficial for the industry and regulators. This in turn could provide more evidence on the impact pollutants have on local environments and, in turn, improve the planning process.

There will also be a focus on the alignment of EF across the devolved nations. The impact and legal implications of this work has sparked conversations and there is a strong intention to align across the board, but each country will follow their own processes to update their standard factors.

Updates on reporting deadlines

The window to report emissions via your Pollution Inventory is open until 28 February 2025. It is also the deadline to submit nitrogen- and phosphorus-reporting data, which is now required for all permitted farms in England.