A computer-implemented method for quantifying greenhouse gases, denoted as GHG, emissions produced by a reactor in a wastewater treatment plant, denoted as WWTP, comprising: at time instant t, obtaining (1001a, 1001b, 1001c) a first 2D image from a first thermographic camera, a first 2D image from a second thermographic camera and a first 2D image from a third thermographic camera, said first 2D images corresponding to views of the plume of the greenhouse gases emitted by said reactor at time instant t; obtaining a first 3D image of the plume of the emitted greenhouse gases from said first 2D images; at time instant t+1, obtaining (1001a, 1001b, 1001c) a second 2D image from the first thermographic camera, a second 2D image from the second thermographic camera and a second 2D image from the third thermographic camera, said second 2D images corresponding to views of the plume of the greenhouse gases emitted by said reactor at time instant t+1; obtaining a second 3D image of the plume of the emitted greenhouse gases from second 2D images; obtaining differences between said first and second 3D images; obtaining from said differences a mass flow of the greenhouse gases emitted by said reactor at time instant t+1; wherein said stage of obtaining a first 3D image and a second 3D image of the plume of the emitted greenhouse gases from said first 2D images is done as follows: for each 2D image captured by each thermographic camera (500, 501, 502), applying an artificial neural network for obtaining (1012a, 1012b, 1012c) a directrix for each 2D image; obtaining (1013a, 1013b, 1013c) contour lines and corresponding contour surfaces parallel to each directrix, and generatrixes for each 2D image, thus obtaining a volumetric surface and associated partial solid; from said partial solids, obtaining said 3D image. at time instant t, obtaining (1001a, 1001b, 1001c) a first 2D image from a first thermographic camera, a first 2D image from a second thermographic camera and a first 2D image from a third thermographic camera, said first 2D images corresponding to views of the plume of the greenhouse gases emitted by said reactor at time instant t; obtaining a first 3D image of the plume of the emitted greenhouse gases from said first 2D images; at time instant t+1, obtaining (1001a, 1001b, 1001c) a second 2D image from the first thermographic camera, a second 2D image from the second thermographic camera and a second 2D image from the third thermographic camera, said second 2D images corresponding to views of the plume of the greenhouse gases emitted by said reactor at time instant t+1; obtaining a second 3D image of the plume of the emitted greenhouse gases from second 2D images; obtaining differences between said first and second 3D images; obtaining from said differences a mass flow of the greenhouse gases emitted by said reactor at time instant t+1; wherein said stage of obtaining a first 3D image and a second 3D image of the plume of the emitted greenhouse gases from said first 2D images is done as follows: for each 2D image captured by each thermographic camera (500, 501, 502), applying an artificial neural network for obtaining (1012a, 1012b, 1012c) a directrix for each 2D image; obtaining (1013a, 1013b, 1013c) contour lines and corresponding contour surfaces parallel to each directrix, and generatrixes for each 2D image, thus obtaining a volumetric surface and associated partial solid; from said partial solids, obtaining said 3D image. for each 2D image captured by each thermographic camera (500, 501, 502), applying an artificial neural network for obtaining (1012a, 1012b, 1012c) a directrix for each 2D image; obtaining (1013a, 1013b, 1013c) contour lines and corresponding contour surfaces parallel to each directrix, and generatrixes for each 2D image, thus obtaining a volumetric surface and associated partial solid; from said partial solids, obtaining said 3D image.