Identification, evaluation and quantification of VOCs as biosecure markers of swine carcass degradation

Swine carcasses were composted using passively-aerated composting system designed by the Canadian Food Inspection Agency during the 2004 Avian influenza outbreak in British Columbia. In this system, swine carcasses were fully covered by plastic sheets due to biosecurity concerns and visual inspection of the swine carcasses was impossible. Monitoring volatile organic compounds (VOCs) released from carcasses was a promising approach to assess progress and completion of the carcass degradation. In this study, VOCs were sampled using solid phase microextraction (SPME). Samples were analyzed using multidimensional gas chromatography-mass spectrometry (MDGC-MS) (a) to develop a comprehensive chemical library of volatile organic compounds emitted during carcass composting, (b) to determine if specific compounds could be correlated with various phases of the composting process and therefore be used to determine completion of composting and, (c) to determine the effects of compost operating parameters on the chemical make-up of gaseous emissions.;A completely new quantification method of measuring VOCs was developed with accuracy ranging from 79.04 to 98.53% and method detection limits ranging from 0.01 to 580 ppbv. Eighty five microm CAR/PDMS was shown to extract the highest amount of analytes at one hour sampling time. Dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be produced during degradation of swine carcass tissues but not produced from decaying plant (envelope) materials. These compounds could serve as marker compounds of swine carcass degradation process. Laboratory studies showed that marker compounds cannot be detected in the headspace when the respiration rates of carcasses decrease to a level of 3.25 mg CO2-C/g VS*d (stable compost). Field studies showed that when carcass degradation was incomplete, detection of marker compounds was still possible in the eighth week of the process. After eight week composting time, the highest concentrations of marker compounds were detected for the carcass samples with the highest respiration rates (least stabilization). No relation was observed between temperature data and degradation rates of carcasses. A better estimate of carcass degradation was made by measuring concentrations of the marker compounds. The highest concentrations of the compounds were detected from the swine carcasses with the highest respiration rates and lowest decomposition. Dimethyl disulfide, dimethyl trisulfide, and pyrimidine were produced from all compost units under various conditions regardless of the plant material, moisture content, porosity and temperature. These compounds were reliable marker compounds that could be followed to test completion of a swine mortality composting process when the carcasses were fully covered by plant materials and plastic sheets due to biosecurity reasons.;Keywords. Compost, Dimethyl disulfide, Dimethyl trisulfide, GC-MS, Mortality, Pyrimidine, SPME, Swine, VFA, VOC...