Assessing the Significance of Fugitive Emissions from a Landfill Biogas Collecting System Using a Quantitative Optical Gas Imaging (QOGI) Method: a Case Study

The biogas collection system in landfills is a crucial environmental safeguard aimed at either recovering gas energy or producing biomethane. However, the unintentional release of biogas during collection and utilization processes poses an environmental risk due to its high greenhouse potential and could significantly contribute to overall odour emissions from landfills. While recent studies have addressed odour emission issues from the landfill surface, there is a notable gap in research focusing on the impact of fugitive biogas emissions on odour impact assessment. The escape of pure biogas from the collection system has an extreme odorous impact compared to biogas emissions from the landfill surface, which are significantly depleted in odour concentration. Moreover, while technical guidelines exist for evaluating biogas dispersion from the landfill surface, comprehensive studies addressing fugitive emissions from landfills are still lacking. This paper proposes an approach for estimating the impact of fugitive biogas emissions on overall odour emissions from a non-hazardous landfill that collects biogas through a network of over 408 vertical wells. Initially, we assessed the mass flow rate of biogas leaks from each fugitive source using Quantitative Optical Gas Imaging (QOGI), a valuable tool in environmental monitoring that provides accurate real-time measurements of gas concentrations and flow rates. QOGI measurements were compared with Flame Ionization Detector (FID) measurements on critical wells to evaluate the technique's reliability. After field validation of biogas fugitive flux measurements, a Langrangian puff model was used to compare overall odour exposure from the landfill, considering scenarios with and without fugitive emissions. The significance of fugitive emissions in terms of odour impact on receptors was assessed at the level of individual biogas wells, driving improvements in landfill biogas collection. This approach enables design engineers and plant managers to reduce fugitive emissions by inspecting and repairing valves and connections within the wellfield system or by expanding the biogas capture network through the addition of new wells.