ASSESSMENT OF ODORS FROM LIVESTOCK WASTES BY A PHOTOIONIZATION DETECTOR, AN ELECTRONIC NOSE, OLFACTOMETRY AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A photoionization detector (PID) and an electronic nose (EN) based on polypyrrole sensors, were evaluated against odour concentration measurement by olfactometry using odours from pig and chicken slurry. Both instruments were less sensitive than olfactometry, the PID and the EN giving responses down to 1,000 and 60,000 Odour Units m(-3) in air, respectively. The EN was better at discriminating between different odours through the pattern of sensor responses. Gas chromatography-mass spectrometry (GC-MS) analysis was used to demonstrate differences in the chemical composition of the pig and chicken odour. Extraction of odorous compounds from slurries by solvent and purging with air gave different chemical profiles. Some of the major odour compounds were chemically unstable, so rapid, portable devices for odour measurement may have considerable advantages.