What you need to know about ammonia emissions factors

In November 2024, AHDB announced new ammonia emission factors for Environmental Permitting Regulations (EPR) were being published on the government website.

It was a milestone for the pork industry, demonstrating how seriously it takes its responsibilities on environmental improvements, and how important data gathering is.

Zanita Markham, AHDB projects and engagements relationships manager (pork), said the revised emissions factors have saved British pig farmers an estimated £15.3m in environmental mitigation costs.

“It was also recognition of the collaborative approach between industry, levy payer investment in AHDB and government agencies,” she said. “This has now led the Environment Agency [EA] to update its ammonia emission factors to bring the standard figures in line with modern livestock rearing practices, nutrition and genetics.”

For permitted pig and poultry farms, these figures are used for Pollution Inventory reporting, and during the permitting process to quantify and assess the effect 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 AHDB’s multi-year ammonia monitoring project and an EA-commissioned ADAS and Rothamsted Research data review of ammonia emission factors for permitted pig and poultry operations in the UK.

What do farms do now?

“Pleasingly, a reduction has been seen for all pig housing systems. The predicted spend of around £15m has been saved in estimated alterations and installations of abatement technologies,” Zanita added.
“But 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 30kg and dry sows, both on fully slatted floor systems. These systems are marginally out, needing 8% and 9% reductions of 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 still reach compliance,” Zanita said.

She explained that various scenarios are accepted as standard:

• Regular removal of slurry (either by scraping, flushing or pumping): For both non-compliant housing systems, this will immediately place pig units in a compliant system. There is now an agreed definition of frequent slurry removal, which is a minimum of weekly. The implementation of this slurry management system can see a reduction in ammonia emissions of 25%.
• Reducing the crude protein in feed: This is recognised to reduce 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 emission factors of 10% for every 1% reduction in dietary crude protein up to a maximum emission factors reduction of 20%. This will need to be evidenced as part of any permit application.

Other available options include:

• 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 beneficial.
• Phase feeding with the addition of amino acids: This is referenced to result in a reduction of 19%.
• High-pressure water fogging: This can see a reduction of 22–30%.
• Polyethylene floating balls: These can contribute to a reduction when placed in slurry channels.
• Slurry acidification: This can lead to a reduction of 75%. However, it is a more costly option for producers.

Self-evidence

Zanita explained that emission factors (EFs) are the preferred option of reporting on an industry average. “But 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 a costly approach,” she said.

“There is also the potential for an alternative approach using nitrogen excretion data to generate farm-specific EFs 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 proposed. If your proposed system or management technique is outside of a crude protein reduction or frequent removal, 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.”

Focus in the future

It had been 20 years since the last large-scale study of ammonia emissions, and there is now recognition that more frequent monitoring could be beneficial for both the industry and regulators.

“This, in turn, could provide more evidence on the effect pollutants have on local environments, and so improve the planning process,” Zanita added.

“There is also focus ahead on the alignment of EFs 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 its own processes to update its standard factors.”