Pilot scale facility to determine gaseous emissions from livestock slurry during storage
Livestock production is a growing source of air pollution, locally and to the wider environment. Improved livestock manure management has the potential to reduce environmental impacts, but there is a need for methodologies to precisely quantify emissions. This paper describes and evaluates a novel storage facility for livestock slurry consisting of eight 6.5-m3 cylindrical units. The stores may be equipped with airtight covers and ventilated during storage or during measurement only. Each store has eight air inlets (160 mm diameter) and a single outlet in the cover connected to a main ventilation duct. The stores can also be used as static enclosures. Ventilation can be regulated within the range of 50 to 250 m3 h–1. A gas sampling line enables sampling of odorants using automatic thermal desorption tubes, ammonia using acid traps, and greenhouse gases using gas sampling bags (pooled samples) or a syringe (time point samples). Complete recovery of CH4 independent of ventilation rate was demonstrated. Vertical profiles of CO2 and CH4 above the slurry surface with and without ventilation and mixing of the headspace indicated methane oxidation activity in the surface crust. p-Cresol and 4-ethyl phenol emission from pig slurry was identified by GC-MS analysis of odor collected on adsorption tubes. Ammonia emissions between 0 and 166 mg N m–2 h–1 were observed during storage of pig slurry with and without surface crust and cover. A comparison of pooled and averaged time point measurements of CO2, CH4, and N2O indicated that pooled samples account for the diurnal variations under realistic storage conditions.