Encouraging ammonia emissions results from the CAFRE dairy herd

Date published: 4 September 2024

Background

In Northern Ireland 97% of ammonia emissions come from agricultural practices with key areas of emission from the management of animal manures and application of nitrogen fertilisers.

Agreed legislative reduction requirements which were set as part of the UN Gothenburg protocol gives the UK a commitment to reduce ammonia by 8% by 2020 and 16% by 2030, based on 2005 levels. However, since then, emissions have risen to 31.98kt in 2021 which sets a new requirement of 25% reduction from this level.

College Estate Strategy and air quality targets

In 2021 the College of Agriculture, Food and Rural Enterprise (CAFRE) developed a College Estate Strategy. The document highlights best environmental practices in all activities across the college with attainment targets for 2030.

“The strategy aligns the work of the CAFRE estate to the principles within the Future Agricultural Policy Framework Portfolio of improved environmental sustainability, increased productivity, improved resilience and an effective, functioning supply chain,” commented Judith McCord, Senior Air Quality Technologist, CAFRE. One of the eight high level targets which will require action to make progress is for CAFRE air quality not to impact on local habitats and health by 2030.

Main mitigation technologies employed at the CAFRE Dairy Centre

Livestock diets

Ration formulation to reduce crude protein (CP) in the CAFRE dairy cow diet has seen the CP decrease from 18% to 16% - Research suggests a reduction of 1% crude protein content in the diet can reduce ammonia emissions by between 5 and 15%. This range is based on stage of lactation and protein requirement in conjunction with forage quality and genetic merit.

Housing management and manure storage

Within the CAFRE Dairy Centre cubicle house floors are scraped every two hours. Alongside more frequent scraping the use of low emission flooring reduces pooling of urine by funnelling it into deeper grooves. This helps to keep manure and urine separate to a greater degree. More frequent scraping of floors (two hours versus four hours) alone can contribute up to a 20% reduction in ammonia emissions. This in combination with the best available flooring systems provides for a reduction of up to 50% compared with traditional practices.

Research on impermeable tensioned fixed slurry covers, which CAFRE has installed on all outdoor above ground slurry stores at the Dairy Centre, gives an emission reduction of 80% when compared with uncovered stores.

Fertiliser and slurry application

For inorganic nitrogen application the CAFRE farms have moved entirely to the use of stabilised urea which has been shown to reduce ammonia emissions in wet climatic conditions by up to 70% when compared to using Calcium Ammonium Nitrate. In terms of manure management CAFRE has been applying slurry using trailing shoe technology for the last number of years. Using low emission slurry spreading equipment (LESSE) has given a 60% reduction when compared with splash plate spreading.

Extended grazing

Increasing days at grass results has been both an economic and environmental gain at the CAFRE Dairy Centre. Grazing removes the need to manage, store and spread manure. Research suggests that increasing the length of the grazing season by one week can result in a reduction in ammonia emissions of 3.5%.

Measuring the complete picture

To be able to establish overall baseline ammonia emissions, data across the CAFRE Farm Centres has been captured to model the complete picture. This summer CAFRE has commissioned AFBI work on nitrogen modelling for the CAFRE Farm Centres. This is to assess the benefits of the legislative and voluntary measures the farm has employed and to establish the total figure for ammonia emissions for each Farm Centre.

Preliminary results suggest that in combination all of the mitigation strategies employed on the CAFRE Dairy Centre provide for a reduction in ammonia emissions of over 25%. More modelling and refining of scenarios are required. The results of which will form part of any future ammonia knowledge transfer programmes.