Abstract
Odorous volatile organic compounds (VOC) and hydrogen sulfide (H2S) are emitted together with ammonia (NH3) from manure slurry applied as a fertilizer, but little is known about the composition and temporal variation of the emissions. In this work, a laboratory method based on dynamic flux chambers packed with soil has been used to measure emissions from untreated pig slurry and slurry treated by solid-liquid separation and ozonation. Proton-transfer-reaction mass spectrometry (PTR-MS) was used to provide time resolved data for a range of VOC, NH3 and H2S. VOC included organic sulfur compounds, carboxylic acids, phenols, indoles, alcohols, ketones and aldehydes. H2S emission was remarkably observed to take place only in the initial minutes after slurry application, which is explained by its high partitioning into the air phase. Long-term odor effects are therefore assessed to be mainly due to other volatile compounds with low odor threshold values, such as 4-methylphenol. PTR-MS signal assignment was verified by comparison to a photo-acoustic analyzer (NH3) and to thermal desorption GC/MS (VOC). Due to initial rapid changes in odorant emissions and low concentrations of odorants, PTR-MS is assessed to be a very useful method for assessing odor following field application of slurry. The effects of treatments on odorant emissions are discussed.
Highlights
Livestock manure slurry is widely used as organic fertilizer in order to utilize the nutrient value of this waste product from animal production [1]
The analyses of these were done by gas chromatography with mass spectrometric detection (GC/MS) on samples collected by adsorption tubes packed with a
Ozonation of the liquid fraction after separation resulted in lower emissions of trimethylamine, whereas NH3 was not affected by ozonation
Summary
Livestock manure slurry is widely used as organic fertilizer in order to utilize the nutrient value of this waste product from animal production [1]. Due to the variation in volatility (e.g., H2S vs 4-methylphenol) and chemical stability it is likely, that the odorant/VOC composition of the emissions may vary over time, which is indicated by the results obtained by Feilberg et al [5] This may affect which key odorants are expected to cause nuisance at different periods after application and may affect the choice of relevant abatement technologies. As an alternative to logistically demanding full scale field trials, emissions can be investigated at laboratory scale using small model systems with an artificial air exchange [15,16], which can be designed to simulate ambient conditions as far as possible [17] This is useful for investigating emission processes under controlled conditions and for obtaining data on odorant composition for different slurry treatments and application techniques. The treatments were included in order to assess if any major changes in chemical composition due to the treatments could be identified
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