Activated carbon derived from Japanese distilled liquor waste: Application as the electrode active material of electric double-layer capacitors

Shochu is a major distilled liquor in Japan, and significant shochu waste (approximately one million metric tons) is discharged every year. Wheat shochu waste was precarbonized at 600 or 700 °C and then processed by KOH chemical activation, producing shochu waste-derived activated carbon (SWAC). The material properties and electrochemical performance of SWAC were investigated to verify its potential use as the electrode active material of electric double-layer capacitors (EDLCs), in comparison with two types of commercially available benchmark activated carbons. The precarbonization temperature had a significant influence on not only the development of pores but also the energy and power densities of the SWACs. Among all the samples, the SWAC precarbonized at 700 °C, with a specific surface area of 2434 m² g⁻¹, exhibited the highest gravimetric specific capacitance of 152 F g⁻¹ and the highest gravimetric energy density of 44 Wh kg⁻¹. The SWAC precarbonized at 600 °C achieved the highest volumetric specific capacitance of 75 F cm⁻³ and a volumetric energy density of 18 Wh L⁻¹ but displayed low power performance. The performance of EDLC electrodes using this distilled liquor-originated biowaste was highly promising.