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

Abstract : The objective of this study was to correlate the chem. compn. and the odor concn. of emissions produced during storage and composting of pig slaughterhouse sludge (PSS). Seven exptl. 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 chem. compn. and the odor concn. (OC) of every gas sample. The odor activity value for a given emitted compd. (OAV) was computed as the ratio of its chem. concn. 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 compd. contained in the gas sample. As per Std. 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 chem. compn. and OC, only three compds. among the 66 identified namely trimethylamine, hydrogen sulfide and methanethiol, accounted for the prediction of OC measured during composting and storage of PSS.