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A newly developed PHP (phosphoric acid plus hydrogen peroxide) pretreatment for lignocellulose is integrated to be a multi-product platform for bioethanol, lignin, and ultra-high surface area carbon; the performances of this multi-product strategy are investigated in this work. Based on PHP pretreatment platform, 100.0 g wheat straw yield 16.0 g ethanol from the cellulose fraction, and 7.2 g high purity lignin can be recovered from the derived liquid fraction in pretreatment. Activated carbon (PHPK-800) with ultra-high surface area of 3291 m2 g−1 can be produced from the water-soluble fractions derived from pretreatment. As electrode material for supercapacitor, PHPK-800 displays an excellent specific capacitance of 303.5 F g−1 at 0.5 A g−1, and retains 87.0% of initial specific capacitance with more than 95.0% coulomb efficiency after 5000 cycles. The fabricated symmetric supercapacitor harvests an excellent energy density of 13.2 Wh kg−1 with 199.9 W kg−1 power density. Besides, a superior CO2 adsorption capability of 4.61 mmol g−1 is achieved by activated carbon of PHPK-700. According to these performances, PHP pretreatment platform is promising for converting lignocellulose into bioethanol, lignin and carbons by the biomass full utilization to achieve a more sustainable lignocellulosic refinery.

Trichoderma is cultivated on a solid medium prepared from wheat straw and food waste. The harvested mixture is fully used to prepare high specific surface carbon. The carbon is further assembled into an electrode to assess its electrochemical performance as a supercapacitor. As adjusted by the activation temperature, the carbon derived at 800 °C displays an extremely high specific surface area of 3977.3 m2 g−1, and the carbon derived at 900 °C shows a large pore volume of 2.372 cm3 g−1. Correspondingly, an excellent specific capacitance of 409.7 F g−1 at a current density of 0.5 A g−1 can be achieved in a three-electrode system. The symmetric supercapacitor achieves a high energy density of 11.3 Wh kg−1 with a corresponding power density of 240.0 W kg−1, and exhibits a good capacitance retention of 99.2% after 10000 cycles at the current density of 5 A g−1 in a 6.0 mol L−1 KOH electrolyte. Based on these results, a novel low-cost path for preparing high-performance materials for energy storage applications is achieved from real-world biomass sources and provides new insights to realize the full utilization of biomass waste.

Composting leachate, a potential precursor, was attempted to prepare the activated carbons via hydrothermal carbonization plus KOH activation in this work. The obtained carbons were further investigated to check their electrochemical performances as electrode materials of supercapacitor. The carbon material that activated at 700 °C (CL-700) exhibits the highest specific surface area of 2184.9 m2 g−1 and the largest pore volume of 1.55 cm3 g−1 comparing to the activated carbons at other temperatures. In a three-electrode system, CL-700 displayed an excellent capacitance of 228 F g−1 at 0. 5 A g−1, and it was 178 F g−1 even though at a higher current density of 10 A g−1. After 5000 tests on the charge-discharge cycle, CL-700 showed a superior stability with 83.2% capacity retention and almost 100% coulombic efficiency at 5 A g−1. Moreover, CL-700 had a good energy density of 7.1 Wh kg−1 at a power density of 124.9 W kg−1 in a symmetric two-electrode system. Based on the comparison with the currently reported biomass-deriver carbons, the composting leachate can be regarded as a feasible precursor to harvest carbon materials for supercapacitor electrode, which was meaningful to offer a novel path for the valorization of the leachate fraction from bio-wastes.