A Comparative Performance Study Using Dynamic Headspace Sampling and Sorbent Tube Methods of Broiler Litter Odour

Demand for meat chicken (broiler) expands extensively with growing population and rise income globally (Miller et al. 2022). Broilers are usually grown on bedding material in ventilated tunnel sheds over 7 – 9 weeks. Though the intensive livestock practice ensures minimal nuisance generation to the surrounding condition, the facilities often become a target for odour complaints due to emerging urban encroachment in the rural environment (Powers et al. 2005). Odours from broiler shed are generally generated through aerobic and anaerobic microbial activities within the litter and from the animals (Rappert and Muller 2005; Dunlop et al. 2016). Occurrence of odour annoyance increase with accumulation of waste sources as litter over chicken growth period. This incident results in annoyance complains from the local residents living near the facility (Schiffman 1998; Modak et al. 2019; Dunlop and Atzeni 2020) and also personnel’sworking in the facility (Marinella et al. 2014). To abate odour in poultry production facilities, accurate sampling and characterisation of odours using reliable and representable techniques are essential to gain a clearer understanding of the emission nature (Schiffman 1998; Lacey et al 2004; Powers et al 2005; Conti et al 2020; Guo et al 2022) and to implement odour guidelines.

Sampling of odours from a matrix at ambient condition is often critical and challenging (Laura et al. 2013). Odorous emissions are combination of varieties of compounds with vast range of quality and quantity (Eva et al. 2011; Shicheng et al. 2010 and Lorenzo et al. 2022). Techniques of volatile collection mostly include solvent extraction, sorbent tubes and solid phase micro-extraction in which involves enrichment and collection of representative volatiles, especially those with low concentration, on a suitable medium prior to analysis (Eva et al. 2010). However, these techniques also may cause losses of volatile organic compounds as the sorbent materials tends to absorb water in high humidity circumstances and during multiple stages of stripping and loading of odours, that may change the characteristics of its components (Noelia et al 2010). Focusing of volatiles onto sorbent materials or cold trap offers adequate approach to obtain micrograms and nanograms per litre of concentrated volatiles, resulting in the least amendments on the gas sample and sample matrix and interference of solvent. The desired volatiles are adsorbed on a sorbent material or cold trap at a preset flow rate prior to thermal desorption. Basic prerequisites are the choice of sorbents which are dependent on the affinity of desired chemical, appropriate breakthrough volume for all volatiles present in a gaseous sample, low water affinity, high recovery of volatiles during thermal desorption, low reactivity with volatiles adsorbed and the absence of the formation of artefacts (Pillonel et al. 2002 and Tholl et al. 2006). No one sorbent material is capable of adsorbing all kinds of volatiles and most sorbent material has affinity towards a particular volatile functionality (Munoz et al. 2002 and Ribes et al 2007). This aspect has led to the development and usage of multi-bed sorbent tubes that enables advanced levels of volatiles’ focusing (Ribes et al. 2007). The most common sorbent materials available commercially include Tenax TA, Chromosorb carbon molecular sieves, graphitized carbon and multi-bedded sorbent materials such as Carbograph, Carbotrap C and Carbotrap/ Carbosieve (Chuandong et al. 2018).

Meanwhile, dynamic headspace sampling technique is used to separate volatiles above a liquid or solid prior to instrumental analysis (Curioni and Bosset 2002). It is a simple technique to collect and analyse volatiles with the least amount of deterioration and amendment of the chemicals (Bart 2001; Tholl et al. 2006; d’Acampora et al. 2008 and Hobbs et al. 2004) and significantly suitable for highly humid/wet samples. Dynamic headspace sampling strips volatiles of a sample matrix in a sample vessel using a continuous flow of a gas stream under non equilibrium conditions (Bianchi et al. 1989). Stripped volatiles are concentrated onto a sorbent material or cold trap prior togas chromatography analysis. Two mode of dynamic headspace sampling volatiles extraction are open stripping and closed stripping (Capelli et al. 2013). In open system, problems related to increases in temperature and humidity or an accumulation of damaging vapours in the headspace that are eliminated by a constant air stream. Whereas, using closed-loop stripping, volatiles, especially analytes with low concentrations, are enriched onto sorbent materials during continuous circulation of the headspace air inside closed chambers with minimum air contaminants. Minor drawback of the headspace sampling techniques is related to the cleanliness of sampling apparatus, but this can be overcome with good laboratory practices to enhance the repeatability and reproducibility of the sampling method (Tholl et al. 2006).

Despite availability of several sampling methods for odorant analysis, identification of suitable method serving the objective of particular experimental analysis is essential. Suitability of a sampling technique depends on many factors including environmental aspectse.gambient temperature, sampling site, costing of analysis, skill of staff and availability of compatible instrument and etc. Moreover, the selection and execution of particular experimental techniques should produce relevant output/result for optimum solution of events. Therefore, this study aims to compare the performance of between Tenax TAsorbent tune and dynamic headspace sampling for odour analysis of broiler litter emission. The broiler litter odour was represented using standard solutions containing 13 major odorants prepared based on literature reviews (Lacey et al. 2004; Steven et al. 2010 and Jiang et al. 2023) The sampling techniques were coupled to thermal desorption, gas chromatography – mass spectrometry and olfactory detection (TD-GC-MS/O) system for determine volatile organic compounds with odorant properties. The TD-GC-MS/O system used provides both instrumental and human sensory evaluation of isolated odorants. The study is expected to provide information on effective and suitable sampling technique selection for fast and reliably point source broiler litter odour analysis at ambient temperature. Olfactory analysis is required significantly in intense livestock facility to mitigated odour as the analysis provides clearer understanding of the emission nature. The TD-GC-MS/O technique is often used in the food, water, aroma and environmental studies to enable determination of volatiles with low threshold levels and offensive qualities responsible unpleasant odour (Kozicki 2022; Dang et al. 2022; Hong et al. 2021).