title: Volatile organic compound emissions from dairy cows and their waste as measured by proton-transfer-reaction mass spectrometry.
abstract: California dairies house approximately 1.8 million lactating and 1.5 million dry cows and heifers. State air regulatory agencies view these dairies as a major air pollutant source, but emissions data are sparse, particularly for volatile organic compounds (VOCs). The objective of this work was to determine VOC emissions from lactating and dry dairy cows and their waste using an environmental chamber. Carbon dioxide and methane were measured to provide context for the VOCs. VOCs were measured by proton-transfer-reaction mass spectrometry (PTR-MS). The compounds with highest fluxes when cows plus waste were present were methanol, acetone + propanal, dimethylsulfide, and m/z 109 (likely 4-methyl-phenol). The compounds with highest fluxes from fresh waste (urine and feces) were methanol, m/z 109, and m/z 60 (likely trimethylamine). Ethanol fluxes are reported qualitatively, and several VOCs that were likely emitted (formaldehyde, methylamine, dimethylamine) were not detectable by PTR-MS. The sum of reactive VOC fluxes measured when cows were present was a factor of 6-10 less than estimates historically used for regulatory purposes. In addition, ozone formation potentials of the dominant VOCs were -10% those of typical combustion or biogenic VOCs. Thus dairy cattle have a comparatively small impact on ozone formation per VOC mass emitted.
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, Hilgard Hall, Berkeley, California 94720, USA. slshaw@alum.mit.edu
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Shaw
authors.forename: Frank M
authors.initials: FM
authors.lastname: Mitloehner
authors.forename: Wendi
authors.initials: W
authors.lastname: Jackson
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Depeters
authors.forename: James G
authors.initials: JG
authors.lastname: Fadel
authors.forename: Peter H
authors.initials: PH
authors.lastname: Robinson
authors.forename: Rupert
authors.initials: R
authors.lastname: Holzinger
authors.forename: Allen H
authors.initials: AH
authors.lastname: Goldstein
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000818:Animals; D002245:Carbon Dioxide / Q000032:analysis; D002417:Cattle; D004784:Environmental Monitoring; D005260:Female; D007774:Lactation; D008372:Manure / Q000032:analysis; D013058:Mass Spectrometry / Q000379:methods; D009930:Organic Chemicals / Q000032:analysis*; D010126:Ozone / Q000737:chemistry*; D011247:Pregnancy; D011522:Protons; D014835:Volatilization
chemical_list: D000393:Air Pollutants; D008372:Manure; D009930:Organic Chemicals; D011522:Protons; D002245:Carbon Dioxide; D010126:Ozone