Supercapacitors, with their high power density and quick charge/discharge capability, have gained attention as the highly desirable energy storage devices. Recent studies have shown that carbon-based materials with high surface area have huge potential for energy storage applications. It will be interesting if such carbon materials can be produced with desirable characteristics using a green approach. Herein, we report a highly reproducible sustainable approach of producing high surface area activated carbons directly from styrene acrylonitrile (SAN) plastics, obtained from the end-of-life printers. Activated carbons had high specific surface area and pore volume due to the mesopores and micropores generated in the carbon skeleton during the activation process, thus making these activated carbons a good potential candidate for supercapacitor electrode fabrication. We have studied the supercapacitance performance of these activated carbons with varied surface areas by conducting electrochemical experiments using a three-electrode system, with 2 M KOH as electrolyte, at scan rates ranging from 5 to 150 mV/s. While being used as a supercapacitor electrode without the addition of any conductive additives such as carbon black, specific gravimetric capacitance values of as high as 220 F/g were achieved. This is an outstanding supercapacitance performance of carbons produced using waste resources.