The Synergy of Olfactometry and Sensorial Analysis – Setting a New Standard to Determine Odour Emission Thresholds for Bref Slaughterhouses and Animal By-products

Processing meat and animal by-products is often accompanied by the release of unpleasant odour. Within the BREF Slaughterhouses and Animal By-Products Best Available Techniques (BAT) are therefore supplied in order to reduce emissions to air of organic and malodourous compounds originating from slaughter and animal by-product processing activities. To determine the efficiency of these BAT’s, BAT-associated emission levels (BAT-AEL’s) are defined for odour concentration, TVOC, NH3 and H2S. In the first draft of the BREF (May 2005) the BAT-AEL of odour concentration was solely defined by olfactometry. Determining the efficiency on olfactometry alone will often provide a biased result as some emission reduction techniques create their own odorous air that might impede the required BAT-AEL. To address the missing link, OLFASCAN developed a sensorial analysis technique to determine the odour characteristics of emission reduction techniques. The analysis involves assessing undiluted air samples, taken before and after the emission reduction technique, by a panel consisting out of minimal six calibrated human examiners. The goal of the analysis is to obtain a qualitative odour assessment by scoring air samples based on their odour intensity and unpleasantness and by supplying an odour description. In combination with olfactometry, the sensorial analysis approach was tested on emission reduction techniques of a rendering facility to showcase the synergy between olfactometry and sensorial analysis in assessing BAT-AEL’s. The following four emission reduction techniques were examined: (I) well-performing biofilter, (II) insufficiently performing biofilter, (III) well-performing thermal oxidation and (IV) insufficiently performing thermal oxidation. The obtained results highlighted two important findings: (I) a high odour removal efficiency according to olfactometry is not necessarily an indication of a properly working reduction technique if process odour can still be determined via sensorial analysis and (II) a high odour concentration at the outlet of the emission reduction technique is not necessarily an indication of an insufficient technique if the process odour is completely absent. From these findings, the BAT-AEL for odour concentration was redefined in the final draft of the revised BREF, stating: “An exception to the BAT-AEL is allowed if, in the case of combustion techniques (BAT-AEL = 1.100 ouE.m-³), the odour abatement efficiency is = 99 % or, as an alternative, process odour is no longer perceptible, or, in case of non-combustion techniques (BAT-AEL = 3.000 ouE.m-³), the odour abatement efficiency is = 92 % or, as an alternative, process odour is no longer perceptible”. The elaboration of a well-defined procedure by OLFASCAN on how to examine odour samples in a qualitative way gives answer to the new rules defined in the revised BREF.