The revised EU Urban Wastewater Treatment Directive (3019/2024) requires wastewater utilities to monitor and report greenhouse gas (GHG) emissions. In response, Gruppo CAP—operating 40 WWTPs serving about 2.4 million people in the Metropolitan City of Milan—joined the Science Based Targets initiative (SBTi) in 2024 (baseline 2021: 185,297 tCO₂eq·yr⁻¹; –42% by 2030) and became, in 2025, the fourth member of the international Net Zero Partnership. Founded in 2022 by Severn Trent Water, Melbourne Water, and Aarhus Vand, the Net Zero Partnership brings together leading utilities to accelerate decarbonization of wastewater treatment through shared innovation, joint R&D, and knowledge exchange, with ambitions to cut over 1 million tonnes of CO₂ annually. Key initiatives include Severn Trent’s Net Zero Hub at Strongford WWTP and collaborative work on fugitive emissions, particularly N₂O and CH₄. Gruppo CAP’s entry expands the partnership to Southern Europe and strengthens alignment with EU policy. Gruppo CAP’s 2024 GHG inventory reports 229,518 tCO₂eq·yr⁻¹, with direct N₂O emissions accounting for 17.4%, underlining the need for direct measurements. Following a 2024 pilot at Bresso–Niguarda WWTP, full-scale campaigns will be conducted in 2026 at six plants using the LESSDRONE system, an autonomous platform for real-time off-gas monitoring. The resulting datasets will refine inventories, support model calibration, contribute to the CLIMWATER project, and enable standardized, replicable N₂O quantification methods, supporting effective mitigation strategies toward net-zero wastewater treatment.