Microsoft Word - 26jonassen.docx CCHHEEMMIICCAALL EENNGGIINNEEEERRIINNGG TTRRAANNSSAACCTTIIOONNSS VOL. 40, 2014 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editor: Renato Del Rosso Copyright © 2014, AIDIC Servizi S.r.l., ISBN 978-88-95608-31-0; ISSN 2283-9216 Evaluation of Abatement Technologies for Pig Houses by Dynamic Olfactometry and On-site Mass Spectrometry Michael J. Hansena*, Kristoffer E.N. Jonassenb, Anders Feilberga a Department of Engineering, Aarhus University, Hangøvej 2, DK-8200 Aarhus N b Pig Research Centre, Danish Agriculture & Food Council, Axeltorv 3, DK-1609 Copenhagen V *michaelj.hansen@eng.au.dk The aim of the present study was to evaluate the effect of abatement technologies for pig houses on odour based on 1) on-site measurements of dynamic olfactometry and chemical odorants and 2) dynamic olfactometry with storage of air samples in sampling bags. The study was conducted at two facilities with growing-finishing pigs with either biological air cleaning or slurry acidification. Five measurements days were carried out at the facility with biological air cleaning and six days at the facility with slurry acidification. A mobile laboratory containing proton-transfer-reaction mass spectrometry (PTR-MS) and an olfactometer was applied for the on-site measurements. The mobile laboratory was connected to the odour sources by insulated and heated Teflon tubes that were flushed continuously with sample air. The sampling bags for dynamic olfactometry were collected simultaneously with the on-site measurements and were analysed after ca. 24 h. At each measurement day three repetition were performed before and after the biological air cleaner and in the pig house with slurry acidification and in an identical control pig house. Odour threshold values for the individual chemical odorants were used to estimate the odour activity value for each sample. The results demonstrated that evaluation of the abatement technologies based on the on-site measurements of dynamic olfactometry and the odour activity value based on chemical odorants were in agreement and showed the same trend in data. However, if the effect of the abatement technologies was evaluated based on dynamic olfactometry with storage in sampling bags the effect of the biological air cleaner was in general underestimated and the effect of the slurry acidification system was overestimated. In conclusion, the storage in sampling bags seems to bias the measurements of odour and this may influence the estimated effect of abatement technologies. More research is needed to limit the bias of sampling bags used for dynamic olfactometry. 1. Introduction Odour nuisance from modern intensive animal production has gained increased attention during recent years and has resulted in development of abatement technologies (e.g. biological air cleaning and slurry acidification). The cleaning efficiency of abatement technologies in relation to odour is normally based on the European standard for dynamic olfactometry (CEN, 2003). However, this method requires collection of air samples in sampling bags that can be stored for up to 30 h before analysis. It has been demonstrated in several studies that the recovery of chemical odorants is impaired by the storage in sample bags (Hansen et al., 2012a; Koziel et al., 2005; Trabue et al., 2006) and this may influence the estimated effect of abatement technologies. It has often been suggested that measurements of chemical odorants could be an alternative to olfactometry. Proton-transfer-reaction mass spectrometry (PTR-MS) has been shown to be a useful method to measure chemical odorants in air from both cattle (Ngwabie et al., 2008; Shaw et al., 2007) and pig production (Feilberg et al., 2010; Hansen et al., 2012b; Liu et al., 2011). The aim of the present study was to develop a mobile laboratory including an olfactometer and a PTR-MS and to evaluate the effect of abatement technologies on odour based on 1) on-site measurements of dynamic olfactometry and chemical odorants and 2) dynamic olfactometry with storage of air samples in sampling bags. DOI: 10.3303/CET1440043 Please cite this article as: Hansen M., Jonassen K., Feilberg A., 2014, Evaluation of abatement technologies for pig houses by dynamic olfactometry and on-site mass spectrometry, Chemical Engineering Transactions, 40, 253-258 DOI: 10.3303/CET1440043 253 2. Materials and methods 2.1 Mobile laboratory A mobile laboratory was constructed in an insulated trailer that was divided into two rooms where one room contained an olfactometer (TO8, Odournet GmbH, Kiel, Germany) and the other room a PTR-MS (High sensitivity PTR-MS, Ionicon Analytik GmbH, Innsbruck, Austria), see Figure 1. The room for the olfactometer was equipped with air conditioning with a charcoal filter in the air inlet. The dilution air to the olfactometer was provided by an air compressor (Dr. sonic, Fini, Bologna, Italy) and before entering the olfactometer the dilution air was filtered by a column containing silica gel and charcoal. The air compressor was placed within 25 m of the mobile laboratory. The mobile laboratory was connected to two odour sources by insulated and heated Teflon tubes (inner diameter: 6 mm and outer diameter: 8mm, Mikrolab A/S, Aarhus, Denmark). The Teflon tubes were ca. 30 m long and were flushed continuously with a diaphragm Teflon pump (Capex L2, Charles Austen Pumps Ltd, Byfleet, UK) with a flow at ca. 7 L min-1. Teflon filters (0.2 µm, POLYVENTTM 16, GE Healthcare Europe GmbH, Brøndby, Denmark) were used in the end of the Teflon tubes to protect the analytical instruments from dust particles. Figure 1: Schematic drawing of the mobile laboratory containing an olfactometer and proton-transfer- reaction mass spectrometry (PTR-MS). 2.2 Abatement technologies The mobile laboratory was applied at two pig production facilities with abatement technologies. A biological air cleaner (Farm AirClean three-step Bioflex, SKOV A/S, Glyngøre, Denmark) was installed at a facility with ca. 350 growing-finishing pig (ca. 30-100 kg). The pig house was designed with one large pen with fully slatted floor and ad libitum dry feed. The ventilation system was a negative pressure system with wall inlets. The biological air cleaner was composed by three vertical filter walls of cellulose pads. Step one and two were 15 cm wide and step three was 60 cm wide. The filter walls in step one and two were irrigated with re-circulated water from a pond beneath the filter walls whereas the filter wall in step three was humidified by the air. A slurry acidification system (Jørgen Hyldgård Staldservice A/S, Holstebro, Denmark) was installed at a facility with ca. 650 growing-finishing pigs (ca. 30-100 kg) and was compared to an identical control facility. The pig houses were designed with 36 pens with fully slatted floor and restricted liquid feed. The ventilation system was a negative pressure system with a diffuse ceiling inlet. The slurry acidification system consisted of a process tank outside the pig house where the slurry was treated daily with sulphuric acid (96%). The slurry was acidified to a pH at 5.5 and afterwards a part of the slurry was flushed back into the pig house and the rest was transferred to a storage tank. 254 2.3 Experimental setup Eight panellists were selected according to the European standard for dynamic olfactometry. At the facility with biological air cleaning five measurements days were performed and at the facility with slurry acidification six measurements days. Four panellists were used each day. At each measurement day three repetitions were carried out at each odour source (before and after biological air cleaner; control versus slurry acidification). At each repetition the concentrations of chemical odorants were measured by PTR-MS and odour concentration by dynamic olfactometry in the mobile laboratory. Simultaneously with the measurements in the mobile laboratory air samples were collected in 30 L Nalophan sample bags and sent to analysis at a stationary laboratory (Danish Technological Institute, Roskilde, Denmark) according to the European standard for olfactometry ca. 24 h after sampling. The olfactometer applied at the stationary laboratory was a TO8 from Odournet GmbH. 2.4 Calculation of odour activity value The odour activity value (∑OAV) for each sample based on the chemical odorants measured by PTR-MS was calculated according to Eq(1), where OTV is the odour threshold value for each of the ten odorants included in the study. Odour threshold values reported by Nagata (2003) were used in the study. (1) 3. Results and discussion In Table 1 the average concentrations of ten chemical odorants measured by PTR-MS at two abatement technologies installed at pig houses with growing-finishing pigs are presented along with the average odour activity value (∑OAV) and the odour concentration measured by dynamic olfactometry in the mobile laboratory (Field odour) and in a stationary laboratory (Lab odour). The chemical odorants presented in Table 1 are considered to be some of the most important odorants found in air from pig houses with respect to concentration level and influence on odour (Hansen et al., 2012a). Table 1: Average concentrations of chemical odorants (ppbv) measured by PTR-MS at abatement technologies installed at pig houses with growing-finishing pigs along with odour activity value (∑OAV) and odour concentrations measured by dynamic olfactometry (OU/m3). Compound OTVa Biological air cleaner Slurry acidification Before After Control Acidified Hydrogen sulphide 0.41 578 62 306 33 Methanethiol 0.07 16 13 5.5 4.0 Dimethyl sulphide 3.0 13 9.3 2.7 2.9 Trimethylamine 0.032 30