In this study, we aim to promote the valorization of technical lignin derived from the pulp and paper industry and develop sustainable and environmentally friendly energy storage devices. Lignosulfonate was used as a precursor, and two different approaches were employed: self-activation and two-stage CO2 physical activation, producing porous carbon (PC) and lignosulfonate-activated carbon (LSAC), respectively. The resulting carbon materials underwent plasma treatment and screen printing before being assembled into supercapacitors with a PVA/H2SO4 gel electrolyte. Pore structure analysis revealed that LSAC exhibited the highest specific surface area of 1015.33 m²/g, while PC achieved 574.41 m2/g. Electrochemical analysis showed that PC, produced via self-activation, achieved the highest areal capacitance of 308.21 mF/cm2, an energy density of 27.39 μWh/cm2, a power density of 0.0665 mW/cm2, and a capacitance retention rate of 103.92 % after 10,000 charge-discharge cycles. In contrast, LSAC, using two-step CO2 activation, attained a higher areal capacitance of 646.78 mF/cm², an energy density of 57.49 μWh/cm², a power density of 0.0667 mW/cm², and 99.13% of capacitance retention after 4,000 cycles. Key processing parameters, including carbonization temperature, pre-oxidation treatment, and activation time, played a crucial role in determining the pore characteristics and electrochemical performance. PC exhibited optimal properties at a carbonization temperature of 1000 °C without any agents. Meanwhile, LSAC achieved its best performance under conditions without pre-oxidation, carbonization at 700°C, activation at 800°C, and a 90-min activation time. The two-step CO2 activation process exhibited superior specific surface area, areal capacitance and energy density. This study successfully demonstrates a clean manufacturing process for lignosulfonate-based supercapacitors, promoting the high-value application of technical lignin and advancing sustainable energy storage solutions.