Fig. 3: Outsized contribution of top emitters.
a, Comparison of the EFs (n = 84) of N2O and CH4, as normalized by influent TN and BOD5, respectively. The secondary treatment process and average flow rate of each facility are depicted, as well as those with and without AD. The top 10% of emitters (n = 9) are denoted by ×. The horizontal and vertical dashed lines represent the 75th percentiles of the N2O (0.036 gN2O gTN−1) and CH4 (0.089 gCH4 gBOD5−1) EFs, respectively. b, Cumulative distribution of the carbon footprint and flow across the measured sites. The vertical dashed black line depicts the top 9 (10.7%) plants, and the horizontal blue and orange dashed lines represent the cumulative fraction of flow and carbon footprint contributed by the top 9 (10.7%) plants, respectively. The carbon footprint is defined as the GWP of each gas (28 for CH4 and 265 for N2O) multiplied by the ER of that gas (\(Q_{{\rm{CH}}_4}\) and \(Q_{{\rm{N}}_{2}{\rm{O}}}\)).
