FIG. 1 is a bird's-eye isometric view showing the front, top, and side of my new ornamental design for a recycling system; FIG. 2 is a front elevational view of the recycling system shown in FIG. 1; FIG. 3 is a rear elevational view of the recycling system shown in FIG. 1; FIG. 4 is a top plan view of the recycling system shown in FIG. 1; and, FIG. 5 is a side elevational view of the recycling system shown in FIG. 1, the opposite side of which is a mirror image.