Composting Plants are a potential source of offensive odors that can create annoyance within communities. Therefore, odors have been rated as the primary concern of the public relative to implementation of composting facilities. Engineers must be conscious of this fact and be familiar with odor generation and control. In this study, dispersion modeling and field inspections were used to quantify the potential odor impact, around a particular Composting Plant site in Lisbon, Portugal. The short-term model ISCST3, developed by the Environmental Protection Agency (US-EPA), was applied to this case study. Field inspections, based on VDI 3940 part II: 2006 were made near the composting Plant.
Given the lack of national legislation or guidelines on this subject, the odor levels evaluation was performed based on German Guideline: Determination and Assessment of Odor in Ambient Air (Guideline on odor in ambient air / GOAA). In these guidelines, odor assessment is based on the concept of the so called odor hour. An hour is called “an odor hour” when, at least 10% of the time within this hour odor is perceived (VDI 3788 part I: 2000). The frequency of occurrence of “odor hours” within a year is then compared to given limit values. These limit values are 10% for residential areas and 15% for industrial areas.
In this work, the odor perception frequency was obtained by converting the odor concentrations, simulated by the dispersion model ISCTST3, to “odor hours”, applying a conversion factor. A period of September 2008 was chosen as baseline data for field inspections, and consequent application of model dispersion. These field inspections revealed an impact on local residents, which exceed the limit value of 10% of odors perception. The dispersion modeling confirmed the obtained values, and demonstrated that the odors frequency perception, from the operation of the Composting Plant, could get to the population at a level higher than the 10% limit, in a region that exceeds 1500 m south to the facility.