Correlation of chemical composition and odor concentration for emissions from pig slaughterhouse sludge composting and storage

• PSS composting and storage gas samples were determined by chemical and olfactory analyses.
• For gas samples, correlations between the chemical composition and its OC was investigated.
• OAVMAX assumed that OC was equal to the sample’s highest OAV value.
• OAVSUM assumed that OC was equal to the sum of all OAV for sample.
• The 3 most odorant compound offered a good prediction of the olfactory results.

The objective of this study was to correlate the chemical composition and the odor concentration of emissions produced during storage and composting of pig slaughterhouse sludge (PSS). Seven experimental conditions were monitored using composting reactors with forced aeration and cells designed to simulate storage. Sixty-six gas samples were collected and characterized by both GC–MS and olfactometry. Two types of correlation were investigated between the chemical composition and the odor concentration (OC) of every gas sample. The odor activity value for a given emitted compound (OAV) was computed as the ratio of its chemical concentration to its odor detection threshold (ODT). The correlation OAVMAX considered that the OC of a gas sample was equal to its highest OAV whereas the correlation OAVSUM considered that the odor of the gas sample was equal to the sum of the OAV of every compound contained in the gas sample. As per Standard EN 13725, both OAVMAX and OAVSUM were compared using a confidence level for OC defined as [OC/1.65 to 1.65 × OC]. Whereas OAVMAX values were within the confidence level of OC for 62% of the 66 gas samples, OAVSUM values were within this confidence level for only 53%. Validating OAVMAX as a satisfying correlation between chemical composition and OC, only three compounds among the 66 identified namely trimethylamine, hydrogen sulfide and methanethiol, accounted for the prediction of OC measured during composting and storage of PSS.