Barn climate and emissions
The average time to renew the air volume in a barn (air exchange rate) is a characteristic parameter to evaluate barn climate (animal welfare) and emissions (environmental impact). The air exchange rate of mechanically ventilated barns is a defined tuning parameter, while its determination is sophisticated in the case of naturally ventilated buildings. Different air flows in the barn mediate the transport of heat, humidity, pollutant gases and particles (e.g., dust and bioaerosols). The air flow patterns are usually very complex and characterised by a large temporal and spatial variability. Emission sources are diffuse and cover the housing system itself (animal metabolism, manure and urine) as well as manure storage and its application to fields. Procedural influences and features of the atmospheric boundary layer near the ground shape the emission and dispersion processes originating from livestock husbandry.
We study air flow processes in and around facilities for livestock husbandry and the resulting air exchange and emission rates with our three-column-concept:
- Long-term on-farm measurements
Since 2004 we study meteorological variables (i.e., air velocity, temperature and relative humidity) and concentrations of pollutant gases in a dairy cattle barn in Dummerstorf in cooperation with the Mecklenburg-Vorpommern State Institute for Agriculture and Fishery. In addition, since 2015 measurements of barn climate are conducted in one of the dairy barns of the Institute for Education and Research in Groß Kreutz.
- Physical modelling
The large boundary layer wind tunnel is used as an evaluation tool to study air flow patterns and the transport of tracer gases in and around naturally ventilated barns. Effects of barn geometry and inflow direction for typical inflow profiles are investigated in the physical model.
- Numeric simulation
Computational fluid dynamics (CFD) supports the investigation of the interaction of different drivers in the model (e.g. inflow, temperature gradients) to evaluate their impact on air flow and transport processes in and around facilities for livestock husbandry. Different turbulence parametrisations (RANS & LES models) are applied depending on the particular research question.
By integrating on-farm measurements with data from the boundary layer wind tunnel, comprehensive data sets are generated which, in combination with the numerical models, promote a further development of the technology and management in animal husbandry that combines aspects of animal welfare and environmental protection.
Current research questions
- Which emission fluxes (at the moment: environmentally harmful and climate relevant gases, soon to be extended to dust and pathogenic particle) originate from livestock husbandry systems? How are they spread into the environment? How can we influence the dispersion?
- Which air flow patterns and air exchange rates are characteristic for a particular barn? How do outdoor climate, animal activity and barn design influence the through flow? What is the resulting barn climate? How are gases, dust and pathogenic particles spread inside the barn?
- Which mitigation potentials for pollutant gases and pathogenic particles are available and how can they be efficiently implemented under on-farm conditions?
- How can the barn climate be optimised using smart ventilation systems?