AFBI on the achievable goals in ammonia reduction

Ammonia emissions from livestock present a major challenge to the Northern Ireland agricultural industry. Funded by the Department of Agriculture, Environment and Rural Affairs (DAERA), the Agri-Food and Biosciences Institute (AFBI) is currently conducting a major programme of research and has released this series of articles to help stakeholders understand the issue and adopt solutions to reduce emissions.

Monday, 29th March 2021, 8:29 am
Dr John McIlroy, AFBI Agri-Environment Branch
Dr John McIlroy, AFBI Agri-Environment Branch

In this, the last article in the series, we take a brief look back over the last 6 weeks and draw conclusions on tackling ammonia emissions from agriculture in Northern Ireland

Ammonia and the need for research

In week one, we discussed the sources and impacts of agricultural ammonia, and the scope of AFBI’s research into the issue. A gaseous form of nitrogen, ammonia is released from animal manures and nitrogen containing fertilisers. Excess amounts of atmospheric nitrogen being deposited on many of our designated nature conservation sites and priority habitats, we learnt, is having an adverse effect on these habitats whose health is dependent on low nitrogen inputs.

The need for research is underpinned by a series of legislative drivers, including legal requirements to protect sensitive habitats and promote biodiversity. Furthermore, while Northern Ireland’s agri-food system plays an important role supporting the UK food system as a whole, it is, as a result a disproportionate contributor to UK ammonia emissions and accounts for 12% of the UK total, despite having only 6% of the UK land area.

The UK has committed to reduce ammonia and other emissions under the Gothenburg Protocol and the National Emissions Ceiling Regulations (2018). The agreed reduction targets for ammonia emissions are 8% by 2020 and by 16% by 2030, based on 2005 levels. Northern Ireland is expected to contribute to meeting these targets. Consequently AFBI, in collaboration with Rothamsted Research and the UK Centre for Ecology & Hydrology have undertaken multiple avenues of scientific research which includes:

(1) Modelling a range of ammonia reduction strategies across NI and the resultant impact on nitrogen deposition on sensitive habitats,

(2) Determining the cost-effectiveness of a range of ammonia reduction strategies,

(3) Determining the potential for ammonia emission reduction at farm-level,

(4) Establishing a new ammonia monitoring network of 28 sites across NI, along with a real-time monitoring station at AFBI Hillsborough,

(5) Surveying for insufficient or incomplete activity data on farm practices and determining emission factors for common Northern Ireland livestock management practices,

(6) Investigating how to lower the crude protein to an optimal level in the diets of cattle, pigs and poultry and the resultant impact on ammonia emissions.

Strategies to reduce ammonia emissions

In week two, we outlined 10 different measures which could be employed to reduce ammonia emissions, and highlighted their potential effectiveness across NI. These measures included:

1. a lower crude protein diet

2. genetic improvement in pigs & poultry

3. an extension to the grazing season

4. low emission livestock housing for cattle

5. improved structure of dairy cow collecting yards

6. low emission livestock housing for pigs & poultry

7. pH adjustment of slurry

8. covering above ground slurry stores

9. low emission slurry spreading

10.stabilised urea fertiliser

These reduction measures were modelled using uptake rates deemed to be realistic over a 5 to 10 year period. This research concluded that a 25% reduction in Northern Ireland’s agricultural ammonia emissions would be achievable through the adoption of the suite of ammonia reduction measures. Although this had a positive and significant impact on reducing the atmospheric nitrogen input at all sites, due to high background levels, the measures resulted in only a few sites achieving ammonia concentrations below their critical level (thresholds to avoid damage). The work concluded that a more geographically targeted approach with measures close to these sensitive sites, complemented with NI-wide measures would be needed.

The cost of tackling ammonia emissions

Week three considered the cost of tackling ammonia emissions and the cost-effectiveness of the different ammonia reduction measures which had been modelled across NI.

The most cost-effective measure was identified as extending the grazing season for cattle by two weeks, at a cost saving of £0.07 per kg of ammonia abated, closely followed by lowering crude protein and the genetic improvement in pigs and poultry which both showed zero cost.

The implementation of eleven measures, at what were considered to be realistic uptake rates, was estimated to give an overall reduction of 8900 tonnes of ammonia emissions across Northern Ireland, a 28% reduction. This was calculated to cost £43.65M annually, compared to business as usual ammonia emissions and based on current livestock numbers.

It is evident that reducing ammonia emissions in Northern Ireland will require investment, but it is worth noting that the adoption of the 5 most cost-effective measures resulted in a 21% reduction in NI agricultural ammonia emissions. This level of reduction would significantly contribute to achieving the 2030 target set for the UK, at a significantly lower cost of £6.63M per annum.

Ammonia monitoring research

Week four explored the research being conducted through both the extended Northern Ireland Ammonia Monitoring Network and the continuous high-resolution ammonia monitoring at AFBI Hillsborough.

28 new ammonia monitoring sites were established across Northern Ireland in March 2019 to ground truth modelled ammonia concentration estimates. Results from the network over the first 12 months of operation show that there is good agreement with modelled estimates of atmospheric ammonia across Northern Ireland. These results provide confidence in the ammonia emission inventory and subsequent modelling process which predict the dispersion of ammonia.

In addition to the extended Ammonia Monitoring Network established across Northern Ireland, AFBI in collaboration with the UK Centre for Ecology & Hydrology (UKCEH) are undertaking a pilot project to illustrate the cause and effect between agricultural activities and atmospheric ammonia concentrations on the AFBI Hillsborough research farm. To achieve its aim, a high-resolution ammonia monitoring station was established to record ammonia concentrations in the vicinity of the farm on a minute-by-minute basis.

Preliminary data from the project show that ammonia peaks can be linked to specific on-farm activities which incur ammonia emissions, and with weather variables such as wind speed, direction and temperature. There is a notable seasonal trend in ammonia emissions, with concentrations increasing in spring with the resumption of slurry spreading, peaking in summer and gradually decreasing over late summer and autumn to reach their lowest levels in winter.

Ammonia mitigation in cattle herds, and for the pig & poultry sectors

During weeks five and six we investigated how the ammonia reduction measures discussed in week two could be effectively applied within the cattle, pig and poultry sectors. Typical practices within these sectors were modelled, and their impact on ammonia emissions determined. It was concluded that, when sector specific ammonia reduction measures were applied, significant reductions in ammonia emissions could be made at farm level. Whilst indoor housing of cattle produces higher emissions than systems adopting grazing, for both types of dairy system a 43% reduction in ammonia emissions can be achieved through the adoption of proven and known ammonia mitigation technologies and strategies. For typical beef systems, reductions of 34-42% are possible, up to 45-55% for pigs and approx. 24% for poultry systems. Additional emission reductions for pigs and poultry, and potentially cattle as well, could be achieved through the adoption of slurry acidification. However, further investigation of the impact of this practice on soil health is required before wide scale adoption could be promoted.

Our understanding of how much ammonia is emitted from specific agricultural practices in Northern Ireland is continuing to improve and further research is ongoing. Current projects focus on ammonia emissions from cattle housed on slatted floors and grazing livestock as well as the extent to which ammonia can be reduced through optimising the crude protein content of cattle diets.

Within the pig & poultry sectors efforts are being made to accurately quantify nitrogen excretion from pigs and broilers, using data from previously published trials conducted at AFBI. Although this project is on-going, preliminary results suggest that nitrogen excretion may be lower than the values in the current NARSES model the UK Inventory. AFBI continues to work with DAERA and the UK National Ammonia Inventory Consortium team to ensure NI specific data are represented appropriately in the reporting of ammonia emissions.

In conclusion

Reducing ammonia emissions is essential to reaching Northern Ireland’s legislative commitments, and to help mitigate the environmental impact of agriculture. It is our hope that the series of articles over the last six weeks has given you an insight into the essential research which is being carried out by AFBI and partners, and an understanding of potential future farm and manure management practices within the Northern Ireland agriculture sector, as reductions in ammonia emissions are pursued. AFBI’s work continues in this area to investigate novel mitigations and further push the boundaries of emission reduction, in tandem with reducing the carbon footprint and phosphorus balance of NI agri-food production.

If you have missed any articles in this series they can all be viewed at www.afbini.gov.uk/news.