From sweet sorghum to supercapacitor and biogas: A new utilization strategy for an energy crop

To seek a possible path to being carbon neutral by using an energy crop, a comprehensive model integrating energy storage and energy supply was developed utilizing sorghum juice as raw material. We prepared a microporous activated carbon with an ultra-high surface area of 3278 m2 g−1 by integrating hydrothermal carbonization, high temperature pyrolysis, and KOH activation. The resulting supercapacitor electrode exhibited a high specific capacitance (314.0 F g−1), exceptional cycling stability (99.3% after 10,000 cycles), and a considerable energy density (8.6 Wh kg−1). Additionally, ∼570 kg ha−1 methane can be produced from the post-hydrothermal waste water through anaerobic digestion, which can compensate for the energy consumed in preparing carbon and allow for a cleaner process. This work offers a novel concept for integrating energy storage, carbon sequestration, and energy supply from energy crops.