Assessment of agricultural waste-derived activated carbon in multiple applications

Abstract

To minimize waste production and reduce reliance on fossil fuels, agricultural waste such as rice straw has been actively used in biochemical production. In Taiwan, cellulosic waste has been used in anaerobic digestion for bioethanol production. This process produces a large amount of biomass-associated sludge that may become a serious environmental issue. Therefore, in this study, the anaerobic digestion sludge was recycled for the production of activated carbon via pyrolysis and activation by KOH. Surface characterization showed increased surface area and development of microporous structure upon activation. The FTIR image showed that high temperature activation eliminated most functional groups in the activated carbon, except for CO and C-O groups. The results showed that the activated carbon could be used for pollutant adsorbents such as molecular dyes (methylene blue: 217 mg g^-1) and metal ions (copper: 169 mg g^-1) from aqueous solution. In addition, the as-synthesized activated carbon can be used for CO₂ capture and capacitor. Instead of focusing on one single application, we proposed that centralized production of activated carbon could be used in various applications, while further modification could be adopted depending on the need of its specific application.

Keywords: Agricultural waste; Anaerobic digestion sludge; Bio-based economy; Pyrolysis; Waste-derived activated carbon.