Emission of odorous compounds from intensive livestock production is a cause of nuisance in populated rural areas. Knowledge on the chemical composition of odor and temporal variations in emissions are needed in order to identify factors of importance for emission rates and select proper abatement technologies. In this work, a method based on proton-transfer-reaction mass spectrometry (PTR-MS) has been developed and tested for continuous measurements of odorant emissions from intensive pig production facilities. The method is assessed to cover all presently known important odorants from this type of animal production with adequate sensitivity and a time resolution of less than one minute. The sensitivity toward hydrogen sulfide is demonstrated to exhibit a pronounced humidity dependency, which can be included in the calibration procedure in order to achieve quantitative results for this compound. Application of the method at an experimental pig facility demonstrated strong temporal variations in emissions, including diurnal variation. Based on these first results, air exchange and animal activity are suggested to be of importance for emission rates of odorants. Highest emissions are seen for hydrogen sulfide and acetic acid, whereas key odorants are evaluated from tabulated odor threshold values to be hydrogen sulfide, methanethiol, 4-methylphenol, and butanoic acid.

No abstract

Separation of slurry produces a solid fraction that is stored in manure heaps before being used as a fertiliser in crop production. Considerable amounts of ammonia (NH 3) and greenhouse gases may be emitted during storage, which has deleterious environmental effects. The emission levels can be expected to depend on oxygenation level inside the bulk of the stored manure and therefore on storage conditions. An experiment was thus set up to study gaseous emissions during storage of the solid fraction, and the effects of the oxygenation of manure heaps on emissions of NH 3 and various greenhouse gases. Emissions of NH 3 and the greenhouse gases methane (CH 4), nitrous oxide (N 2 O), and carbon dioxide (CO 2) from an uncovered and covered heap of solids separated from pig slurry were compared, and related to the oxygenation level inside the manure heap. Approximately 15% of the initial nitrogen content was lost when separated solids were stored uncovered. Of the initial nitrogen content, 4.8% was lost as N 2 O, 0.3% was lost as NH 3 , while the 9.6% unaccounted for was assumed lost as dinitrogen (N 2). Of the initial carbon content, 28% was lost during uncovered storage; the majority of this was emitted as CO 2 (25%), while 1.3% was emitted as CH 4. Oxygenation level inside the heap was found to influence the production and emission of greenhouse gases. Covering the heap with an airtight material delayed aeration of the bulk of the stored manure, which reduced the internal heat production, degradation of organic matter, and emission of NH 3 and greenhouse gases. Emissions of NH 3, N 2 O, and CH 4 were reduced by 12%, 99%, and 88%, respectively, when the manure heap was covered with an airtight material.

Liquid manure (slurry) storages are sources of gases such as ammonia (NH(3)) and methane (CH(4)). Danish slurry storages are required to be covered to reduce NH(3) emissions and often a floating crust of straw is applied. This study investigated whether physical properties of the crust or crust microbiology had an effect on the emission of the potent greenhouse gases CH(4) and nitrous oxide (N(2)O) when crust moisture was manipulated ("dry", "moderate", and "wet"). The dry crust had the deepest oxygen penetration (45 mm as compared to 20 mm in the wet treatment) as measured with microsensors, the highest amounts of nitrogen oxides (NO(2)(-) and NO(3)(-)) (up to 36 mumol g(-1) wet weight) and the highest emissions of N(2)O and CH(4). Fluorescent in situ hybridization and gene-specific polymerase chain reaction (PCR) were used to detect occurrence of bacterial groups. Ammonia-oxidizing bacteria (AOB) were abundant in all three crust types, whereas nitrite-oxidizing bacteria (NOB) were undetectable and methane-oxidizing bacteria (MOB) were only sparsely present in the wet treatment. A change to anoxia did not affect the CH(4) emission indicating the virtual absence of aerobic methane oxidation in the investigated 2-mo old crusts. However, an increase in N(2)O emission was observed in all crusted treatments exposed to anoxia, and this was probably a result of denitrification based on NO(x)(-) that had accumulated in the crust during oxic conditions. To reduce overall greenhouse gas emissions, floating crust should be managed to optimize conditions for methanotrophs.