Slurry acidification in dairy barns

Photo: Peter Kai


The purpose of the project is 1) to verify the effect of slurry acidification in dairy barns on emissions of ammonia, methane and odorants, 2) to optimise the design and management of manure systems in dairy barns with interconnected slurry channels, and 3) to improve the scientific basis for measuring emissions including odorants in naturally ventilated animal houses.

Verification of the environmental effect of slurry acidification will be carried out through an extensive, systematic measuring program in two to four dairy barns that apply slurry acidification in accordance with the VERA test protocol for animal housing and management. State-of-the-art instrumentation will be applied to measure ammonia, carbon dioxide, methane and odorants including Cavity Ring-Down Spectroscopy (CRDS, Picarro inc.) (NH3, CO2, CH4) and Proton-Transfer-Reaction Mass Spectroscopy (PTR-MS) (chemical odorants).

Expected significance for the Danish farmers

In order to meet environmental requirements laid out by Danish law including BAT, Danish farmers must apply environmental technology listed on the Danish EPA List of Environmental Technologies.

The project will provide the necessary documentation required for permanent admission of slurry acidification on the Danish Environmental Protection Agency’ List of Environmental Technologies. Due to lack of sufficient documentation, slurry acidification in dairy barns is currently listed on the list of environmental technologies on dispensation.

Further, we will establish a best practice, including design and management for slurry acidification in dairy barns with interconnected slurry channels.

Expected societal significance

Increased application of efficient, robust technology is a prerequisite for Denmark to meet the international obligations in terms of reducing emissions of ammonia and greenhouse gases. Slurry acidification reduces emissions of both ammonia and methane. However, the effects extend beyond the barn and include reduced emissions during storage of the slurry and during application of the slurry on arable land, i.e. the accumulated effects are high.

Over the last decades, the average barn size has increased. However, with the increasing size of dairy barns, the risk of exposing neighboring areas to annoying odour levels increases with increasing number of heads. The project will increase the knowledge of the sources of odorants in dairy barns, including the composition of chemical odorants.


Project title
Slurry acidification in dairy barns – effect on emissions of ammonia, methane, and odorants.

Danish title: Gylleforsuring i kvægstalde – effekt på udledning af ammoniak, metan og lugtstoffer.

Financial framework
Total budget: DKK 4.418 Million.

The Danish Milk Levy Foundation (Mælkeafgiftsfonden): DKK 3.848 Million.

2018 – 2019

Project partners
SEGES Anlæg og Miljø

About the research section


Peter Kai