Case studies in the use of source specific odour modelling guidelines

Two case studies are compared where source specific odour modelling guidelines have been used: odour emissions from a new brewery and odour from stabilised wastewater biosolids proposed for use in a quarry rehabilitation. In the case of brewery odour, two odour modelling guidelines were used to assess the effects of the proposed brewery operation on a green-field site: 8 OU/m³ at the 99.5th percentile and 6 OU/m³ at the 98th percentile. These guidelines were selected based on published guidance in the United Kingdom which demonstrates that industries with more offensive odour have a different odour exposu re criteria than those with lower offensiveness. For an assessment of digested, stabilised biosolids covered with topsoil, a modelling guideline of 6 OU/m³ at the 99.5 th percentile was proposed, based on a dispersion mod elling calibration and field observations of a similar existing operation. The two case studies show that there is no single odour standard or guideline that will fit all processes and types of odours. The “one size fits all” threshold which assumes all odours hav e the same nuisance threshold is shown to have limitations, in particular, when assessing effects of odours which may not normally be considered offensive.