Landfill Odor Analysis – Monitoring or Dispersion Modeling and AERMOD modeling Assessment

Landfill odor evaluations are essential to communities to manage waste in a way that is good for the planet.   In some cases, landfills also produce significant odor complaints, most notably associated with releasing hydrogen sulfide, a gas with a low odor threshold and rotten eggs odor.   Depending on the sequencing of the cells at a landfill, certain areas may release more or less gas, i.e., the releases are not necessarily uniform across the full extent of the landfills.  Our staff can monitor or model odors and other releases using software such as AERMOD.

Sullivan Environmental specializes in characterizing landfill odor from complex fugitive area sources that impact landfills. We have developed two techniques to calculate the emission rates of chemicals such as hydrogen sulfide. The first is the profile method, which collects concentration and wind data using masts between 0.3 meters and 3-6 meters high. We utilize the integrated horizontal flux method for this approach. The second method is the back-calculation method, which relies on measured concentrations around the perimeter of the source.  

This method combines with normalized air quality dispersion modeling to back-calculate the emission rate. If multiple areas need to be evaluated, we can determine several source areas simultaneously, provided adequate upwind monitoring at each location ensures accurate isolation. The back-calculation method can also assess composite airborne emissions from wastewater lagoons.

Once we identify the emission rates, we can use air model software to show the worst-case scenarios, average conditions, and frequency analysis related to odor thresholds. We typically utilize the AERMOD dispersion model for most applications, while the CALPUFF model is used for specific cases.

Sullivan Environmental has extensive air quality monitoring equipment to support our air quality programs, including the following (partial list):

• 46 air quality sampling systems that sample the air quality based on validated methods.
• 15 sonic anemometers to support multiple meteorological sampling profiles to complement air quality monitoring and support data interpretation.
• 2, 3-dimensional sonic anemometers to provide heat flux data and three-dimensional turbulence data to support air quality modeling initiatives further.
• 3 Odor sampling systems to support the collection of odor samples for presentation to odor laboratory panels.
• two soil monitoring systems to measure soil temperature and soil moisture at multiple sampling depths.