A review of landfill odors assessment: Advancing from stationary measurement to spatiotemporal monitoring

Abstract

Odor issues from landfills remain a persistent environmental challenge, exacerbated by the increasing urbanization and the decreasing proximity of residential areas to waste disposal sites. Conventional odor measurement methods (e.g., olfactometry, gas chromatography-mass spectrometry) have been instrumental in studying landfill emissions and addressing odor complaints. However, these methods either rely on subjective human assessment or require bulky equipment, limiting their large-scale applications on landfill sites. Additionally, real-time odor measurement is hindered by the need for on-site air sampling followed by detailed panel or lab analysis. To overcome these limitations, there is a need to modernize landfill odor assessment through automation, enabling air sampling and analysis with rapid response to odor complaints. Scaling these odor sensors for instantaneous, widespread measurement presents challenges due to the complex and highly variable composition of landfill gaseous emissions. The primary odorants include volatile compounds (VCs) (e.g., hydrogen sulfide, ammonia) and volatile organic compounds (VOCs) (e.g., aromatic hydrocarbons, organic acids). This work explores the current state-of-the-art olfactory-based and analytical-based methods for landfill odor assessment and examines the latest advancements in automated platforms for large-scale measurement, such as unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs). This work also discusses the integration of graphic information system (GIS) and digital twin (DT) technologies for high-resolution spatiotemporal odor mapping and multi-modal data analysis (e.g., zoning, building classifications). Furthermore, the study provides insights into the future convergence of artificial intelligence (AI)-driven analytics, hybrid sensor technologies, and cost-effective scalable solutions to enhance landfill odor assessment and policy development.