Methane (CH 4 ) and nitrous oxide (N 2 O) are potent greenhouse gases with global warming potentials (expressed in terms of CO 2 -equivalents) of 28 and 265, respectively. When emitted to the atmosphere, they significantly contribute to climate change. It was previously suggested that in wastewater treatment facilities that apply anaerobic sludge digestion, CH 4 continues to be emitted from digested sludge after leaving the anaerobic digester. This paper studies the CH 4 and N 2 O emissions from anaerobically digested sludge in the subsequent sludge treatment steps. Two full-scale treatment plants were monitored over a 1-year period. Average emissions of CH 4 and N 2 O were 509±72mg/m 3 -influent (wastewater) and 7.1±2.6mg/m 3 -influent, respectively. These values accounted for 22.4±3.8% of the indirect reduction in CO 2 -emissions when electricity was generated using biogas. They are considered to be significant.