Ammonia Emissions from Agriculture in Switzerland for 1990 to 2020

Ammonia emissions from the Swiss farming sector have scarcely declined over the past 20 years. This is because the factors leading to either an increase or decrease in emissions have for the most part cancelled each other out between 2000 and 2020.

In agriculture, ammonia is mainly produced by the decomposition of urea in livestock excreta. It is emitted to the atmosphere and is partially transported with the wind into sensitive ecosystems such as forests, nutrient-poor grasslands and bogs, where it leads to eutrophication and acidification of the soil and endangers biodiversity. Ammonia also contributes to the formation of particulate matter, thereby negatively affecting human health. For agriculture, ammonia emissions also mean a loss of nitrogen fertiliser.

2018 report updated and expanded

In the course of international agreements with the United Nations Economic Commission for Europe (UNECE), Switzerland is committed to complying with the specified phased emission caps as well as to periodically calculating its ammonia emissions and reporting on the results.

On behalf of the Federal Office for the Environment and with the support of Oetiker + Partner AG and Agroscope, the School of Agricultural, Forest and Food Sciences HAFL has updated and expanded the report on ammonia emissions from 1990 to 2015, originally published in 2018. 

In 2020, animal production accounted for 93% of the agricultural sector’s ammonia emissions. The remaining 7% came from crop production. Cattle produced the highest ammonia emissions in livestock farming, accounting for 77% of emissions in the sector (Fig. 1a). Comparing the different steps of the manure cascade – i.e. the processes in which ammonia is emitted –shows that most ammonia is produced by farm-manure spreading (44%) as well as in the housing and outdoor-exercise yards (36%) (Fig. 1b).

Stagnating decrease in emissions since beginning of 2000

Although ammonia emissions in the Swiss agricultural sector have declined by 23% since 1990 (Fig. 2), the greatest decrease was recorded before 2004. The main reasons for this were the decrease in livestock numbers and the lower use of nitrogen fertilisers after the introduction of the requirement for a balanced nitrogen and phosphorus budget in the Direct Payment Ordinance.  

Ammonia emissions also reflect the change in livestock numbers within animal production, with total cattle and pig numbers since 1990 declining by 18% and 28% respectively, whilst poultry numbers have more than doubled. Accordingly, cattle emissions fell by 16% and pig emissions by 49%, whilst poultry emissions rose by 32%.

Inhibiting and facilitating factors cancel each other out

A countervailing trend can also be seen in emission levels: On pastures, emissions have increased by 85% since 1990 owing to an increase in grazing., However, less of the nitrogen excreted on the pasture is lost as ammonia than of that excreted in the housing, since the urine quickly seeps into the soil. Emissions from housing and outdoor exercise yards also rose by 19%, since the trend towards animal-friendly loose housing systems for cattle and multiple-area pens and a yard for pigs has led to larger emission areas. By contrast, emissions from manure stores fell by 17% and from manure spreading by 41%, in the latter case thanks to the increased use of low-emission spreading technology. Thus, the factors leading either to an increase or decrease in emissions over the period studied largely cancelled each other out, in particular between 2000 and 2020.