This research aims to contribute to promoting a circular economy for technical lignin derived from the pulp and paper industry and developing sustainable and environmentally friendly energy storage solutions. Lignosulfonate was used as a precursor, and a three-stage carbonization method was employed to produce the electrode material. Porous carbon was successfully prepared through a self-activation process without the use of any activating agents. The resulting porous carbon was subjected to plasma treatment and screen printing, and assembled into a supercapacitor with a PVA/H2SO4 gel electrolyte. The results showed that carbonizing temperature at 1000°C boasts the highest specific surface area of 531.158 m2/g, a maximum area capacitance of 308.21 mF/cm2, the highest energy density of 27.39 μWh/cm2, and the power density of 0.0665 mW/cm2. These impressive results demonstrate the successful development of a lignosulfonate-based supercapacitor using a clean manufacturing process. This achievement can promote the high-value applications of technical lignin.