Analytical Sciences, Short talk

Methane, ammonia and volatile organic compound emissions at herd level in an experimental housing for dairy cows

S. A. Wyss1, S. Schrade2, M. Hill1, M. Zähner2, K. Zeyer1, F. Dohme-Meier2, S. Reimann1, J. Mohn1*
1Empa, Laboratory for Air Pollution / Environmental Technology, 8600 Dübendorf, Switzerland, 2Agroscope, Ruminants research unit, Tänikon, 8356 Ettenhausen, Switzerland

Agricultural activities, such as dairy farming, significantly contributes to the Swiss methane (CH4) and ammonia (NH3) emissions [1, 2]. Furthermore, dairy farming seems to be also a relevant source for non-methane volatile organic compounds (NMVOCs) [3].

We will present CH4, NH3 and NMVOC emission data for silage-based versus silage-free (hay) feeding collected at the experimental dairy housing for comparative emission measurements at Agroscope, Switzerland. The housing consists of two identical naturally ventilated compartments, which are spatially separated, to provide an opportunity for comparative quantification of emissions using different diets, housing concepts or management. Mass flow emissions in the naturally ventilated housing were determined using a dual tracer ratio technique, which is suitable for both areal and point emission sources and achieves an uncertainty of less than 10 % [4]. Applying different artificial tracer gases in both compartments, sulfurhexafluoride (SF6) and trifluoromethylsulfur pentafluoride (SF5CF3), cross-contamination events can be detected. Tracer gas mole fractions were analysed by GC-ECD. NMVOC concentrations were determined using different analytical techniques, such as GC-FID and a total hydrocarbon monitor (THC). CH4 and NH3 concentrations were quantified using cavity ring down spectroscopy.

In summary, this study provides currently unavailable information about the emission of CH4, NH3 and NMVOCs emitted from Swiss dairy farming using silage-based vs. silage-free diets. NMVOC emissions in the compartment where silage-based diet was applied were dominated by ethanol (EtOH) followed by ethyl acetate (EtOAc) and methanol (MeOH). These components are produced by bacteria for example during fermentation and storage of silage. In the second compartment, receiving a silage-free diet, NMVOC emissions were substantially lower and concentration differences between EtOH, EtOAc, MeOH and acetone were less pronounced.

[1] FOEN, Switzerland’s Greenhouse Gas Inventory 1990–2014, 2016, 629.
[2] Kupper, T., et al., HAFL, 2013, 110.
[3] Bühler, M., HAFL, 2018, 78.
[4] Mohn, J., et al., Atmospheric Environment, 2018, 179, 12–22.