Combined innovations can deliver ammonia reduction of up to 54%

Date published: 30 April 2025

Introducing management strategies to help reduce ammonia emissions and lessen the impact it has on the surrounding environment is crucial.

However, it is firstly important to understand the emission sources and magnitude of nitrogen (N) release to navigate the ‘pinch points’ on farm where you can employ innovative technologies to achieve maximum impact.

Senior Air Quality Technologist, Judith McCord states that modelling of the CAFRE Dairy Centre inputs through the National Ammonia Reduction Strategy Evaluation System (NARSES) allowed the flow of total N and total amount of ammoniacal N (TAN) to be quantified. The use of this farm ammonia modelling tool identified where ammonia is produced and how N is managed through the farm enterprise cycle.

The ammonia assessment was compiled using farm data relating to herd and manure management from three age stages of livestock: dairy cows, dairy calves 0-1yr and dairy replacements 1-2 years. CAFRE commissioned AFBI to work on the modelling of farm ammonia emissions with and without ammonia mitigation technologies applied. The modelling assessed a range of legislative and voluntary measures implemented at the CAFRE Dairy Centre.

Results

Ammonia emissions for the CAFRE Dairy Enterprise for the year modelled amounted to 3.54 tonnes. This scenario comprised as follows:

• 187 Holstein Friesian dairy cows
• 30% Replacement Rate
• 100% Stabilised urea used on grazing and forage ground (no calcium ammonia nitrate)
• 100% use of low emission slurry spreading equipment (LESSE)
• Targeted and reduced crude protein (CP) diet of 17% for the milking herd
• Low emission flooring in the milking cow cubicle house and high frequency scraping
• All above ground slurry stores covered with an impermeable cover 

The non-mitigated comparison modelled comprised as follows:

• 100% Calcium Ammonium Nitrate (CAN) (no stabilised urea)
• Splash plate slurry application
• No targeted or reduced dietary protein
• Standard concrete flooring with limited scraping
• Open above ground slurry stores

This scenario resulted in modelled emissions of 6.61t NH₃ /year.

At the CAFRE Dairy Centre lactating dairy cows had 48% lower ammonia emissions when there were mitigation strategies implemented in comparison to having no mitigation strategies in place. The dairy replacement enterprise and dairy calves had 55% and 68% lower ammonia emissions respectively when the relevant mitigation technologies were applied. Judith commented that: “this is a very encouraging result” and that “the use of ammonia reducing technologies on Northern Ireland farms will help the sector reduce ammonia emissions.”

Emission sources

The biggest hotspots for emissions within the CAFRE Dairy Centre were in the milking cow category and from manure handling during housing and spreading.  Housing emissions account for 42% of the total both in mitigated and non-mitigated scenarios however mitigation technologies modelled in housing such as low emission flooring and reduced protein diets accounted for reductions of 0.78 and 0.34t/yr respectively. Emission sources on farm showed positive reductions in manure spreading and manure storage where the use of LESSE and impermeable covered slurry stores accounted for approximately 2t/yr combined reductions. The use of protected urea, in the mitigated scenario reduced the amount of total GHG emissions produced in comparison to unprotected urea.

Judith again highlights: “Mitigation strategies that can be implemented at various stages of the system will help to reduce ammonia emissions. Demonstrated clearly at CAFRE - the efficient management of nitrogen can contribute to a reduction of ammonia emissions by up to 54%.” The Top 3 ammonia reduction technologies to apply on farm based on the CAFRE ammonia emissions scenarios are: 100% use of LESSE, installing low emission flooring which has an ammonia efficiency factor of 11kg NH3 alongside high frequency scraping (every 2 hrs) and reducing CP in milking cow diets by up to 2%.

CAFRE Technologists are continuously investigating innovative systems and technologies to help farmers improve sustainability and profitability. These innovations are demonstrated across the CAFRE Farms and form an integral part of CAFRE Knowledge Transfer Programmes. More information on Sustainable Land Management innovations can be found on the CAFRE website.