Achieving carbon neutrality in wastewater treatment plants (WWTPs) by 2060 requires effective strategies to mitigate greenhouse gas (GHG) emissions. This study explores the potential of flexible carbon source regulation to reduce GHG emissions while improving the nutrient removal efficiency under varying influent conditions. A plant-wide model was developed, calibrated with one year of hourly monitoring data, to quantify GHG emissions in a full-scale WWTP. We evaluated three carbon regulation strategies: anaerobic digestion (AD), short fermentation (SF), and adaptive carbon source regulation (ACSR). Results show that AD was most effective in high carbon-to-nitrogen (C/N) ratios, reducing GHG emissions by 29.2%. SF performed best at low C/N ratios, reducing N