Measuring and Modeling Odors from Green Waste Composting Operations

Assessing the potential odor impacts from green waste composting operations presents several unique challenges, both for the measurement of the odor emissions and for the dispersion model simulation of potential odor impacts downwind. In this case study, an extensive odor emissions sampling program was designed and implemented to characterize the odor emissions from the various processes at an existing green waste composting operation, ranging from initial dumping and shredding, through three stages of windrow turning and aging, to final bagging of the compost material. Emission levels and odor character were found to change with aging time and with certain process operations, such as shredding and windrow turning. Spatial variability in emissions was important both for the location of primary, secondary, or tertiary windrows on the property, and also for the sampling location on each windrow from top to bottom. The sampling program attempted to characterize odor emissions based on both time and location. Wind tunnel and surface isolation flux chamber sampling with odor panel analysis were performed for comparison of results. The convective emission flow due to the heat released from composting influenced both the sampling approach and the subsequent dispersion modeling of impacts. Both AUSPLUME and CALPUFF models were used to simulate downwind odor impacts and their results are compared. Special considerations were developed to account for the added buoyancy due to the heat released from the tops of the primary and secondary windrows. The results of the program were used to assess the potential impacts of a new facility on nearby sensitive receptors.