Synthesized biomass-based carbonaceous materials from Palmae plant wastes with self-adhesive properties, converted into coin-like shapes, are used as supercapacitor electrodes with high power and energy density, high specific capacitance, excellent electrical conductivity, low cost, and environmentally friendly. Therefore, this study aims to investigate a simple and cost-effective method to generate porous carbon activation from Palmae plant waste biomass, namely areca leaf midrib (ALM). Activated carbon (AC) material derived from ALM was obtained through precarbonization, alkaline chemical activation, and two-step pyrolysis, namely carbonization and physical activation at 600 °C and 700 °C in the N2 as well as CO2 atmosphere, respectively. Its physical properties show an sp2 structure with high graphitization or amorphousness and two sloping peaks in the hkl plane at an angle of 2θ, approximately 24 deg and 44 deg. The electrochemical properties of AC supercapacitor cells derived from ALM biomass have the highest specific capacitance value of 216 F g−1 at a scan rate of 1 mV s−1 in a two-electrode system. Furthermore, the cell obtained a maximum energy density of 11 W h kg−1 and a power density of 196 W kg−1, respectively. Therefore, this study recommends an innovative and environmentally safe approach for producing high-performance supercapacitor cell electrodes for energy storage without adding nanomaterials and externally doped heteroatoms.