title: Relationships between dairy slurry total solids, gas emissions, and surface crusts.
abstract: Livestock slurry storages are sources of methane (CH₄), nitrous oxide (NO₂), and ammonia (NH₃) emissions. Total solids (TS) content is an indicator of substrate availability for CH₄ and N₂O production and NH₃ emissions and is related to crust formation, which can affect these gas emissions. The effect of TS on these emissions from pilot-scale slurry storages was quantified from 20 May through 16 Nov. 2010 in Nova Scotia, Canada. Emissions from six dairy slurries with TS ranging from 0.3 to 9.5% were continuously measured using flow-through steady-state chambers. Methane emissions modeled using the USEPA methodology were compared with measured data focusing on emissions when empty storages were filled, and retention times were >30 d with undegraded volatile solids (VS) remaining in the system considered available for CH₄ production (VS carry-over). Surface crusts formed on all the slurries. Only the slurries with TS of 3.2 and 5.8% were covered completely for ∼3 mo. Nitrous oxide contributed <5% of total greenhouse gas emissions for all TS levels. Ammonia and CH₄ emissions increased linearly with TS despite variable crusting, suggesting substrate availability for gas production was more important than crust formation in regulating emissions over long-term storage. Modeled CH₄ emissions were substantially higher than measured data in the first month, and accounting for this could improve overall model performance. Carried-over VS were a CH₄ source in months 2 through 6. The results of this study suggest that substrate availability regulates emissions over long-term storage and that modifying the USEPA model to better describe carbon cycling is warranted.
authors.affiliation: School of Environmental Sciences, Univ. of Guelph, ON, Canada. woodj@uoguelph.ca
authors.forename: J D
authors.initials: JD
authors.lastname: Wood
authors.forename: R J
authors.initials: RJ
authors.lastname: Gordon
authors.forename: C
authors.initials: C
authors.lastname: Wagner-Riddle
authors.forename: K E
authors.initials: KE
authors.lastname: Dunfield
authors.forename: A
authors.initials: A
authors.lastname: Madani
mesh_terms: D000393:Air Pollutants / Q000737:chemistry; D000641:Ammonia / Q000737:chemistry*; D000818:Animals; D002170:Canada; D002417:Cattle; D003612:Dairying; D004784:Environmental Monitoring; D008697:Methane / Q000737:chemistry*; D009609:Nitrous Oxide / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D000393:Air Pollutants; D000641:Ammonia; D009609:Nitrous Oxide; D008697:Methane