Satellite-Based Assessment of NH₃ and CH₄ Levels around Biogas Facilities in Izmir

Abstract. This study investigates atmospheric ammonia (NH₃) and methane (CH₄) concentrations in relation to biogas and biomass facilities in Izmir, Türkiye, using satellite-based remote sensing data from 2019 to 2023. NH₃ levels were retrieved from IASI instrument, and CH₄ from TROPOMI instrument, complemented by meteorological observations and livestock production statistics. Results showed that Izmir exhibited the highest NH₃ concentrations across Türkiye, with annual mean levels rising by 43% between 2019 and 2023, and 2023 wintertime NH₃ nearly doubling relative to 2019. CH₄ concentrations also displayed marked increases, particularly after 2021, with maxima recorded in 2022–2023. Spatial and seasonal analyses revealed a persistent hotspot in the inland basin surrounded by the Bozdag Mountains, where intensive livestock farming and multiple biogas facilities are concentrated. Within a 12 km radius of three plants (B64, B67, B68), NH₃ concentrations rised following their operating, though overlap between neighbouring facilities complicates source attribution. While livestock farming and agricultural waste remain the dominant drivers, these findings indicated that biogas and biomass plants may also contribute to elevated NH₃ and CH₄ concentrations in their vicinity. These results emphasized the importance of balancing the renewable energy benefits of biogas expansion with its potential atmospheric impacts in Türkiye.