CO2-assisted thermochemical platform for simultaneous production of supercapacitor electrode and high value fuels from pine sawdust

Abstract

The upcycling of lignocellulosic biomass waste has received particular attention in terms of sustainable waste management and the recovery of value-added products. However, rigid and complicated lignin-rich biomass is rarely used because of its limited applications. Here, we constructed a strategic pyrolysis platform for the recovery of value-added three-phase products: energy storage materials, biofuels, and energy-intensive gas. Pine sawdust (PSD) pyrolysis produced highly porous biochar (surface area: 737 m2 g−1) when CO2 was introduced as a flow gas without further activation processes. The PSD biochar electrode showed a large specific capacitance (337.54 F g−1) compared to other biochar activated by vigorous chemical treatment. The current products of PSD pyrolysis are bio-oil and pyrolysis gas, which can be used as biofuels and platform chemicals. The heating value of bio-oils was > 24 MJ kg−1 without further upgrading. The major gaseous products are CH4 and syngas (H2/CO), which can serve as gaseous fuels or as feedstocks for fine chemical synthesis. The estimated energy yield from the gaseous products was 11.05 MJ kg(PSD)−1 under the CO2 condition, which is 4.35 times higher than N2 condition. Here, the pyrolysis of lignocellulosic biomass waste under CO2 produced porous biochar with acceptable electrochemical performance for use as a supercapacitor electrode, and value-added oil and gaseous fuels were obtained. Therefore, a thermochemical platform with CO2 can be used to produce energy storage materials, beneficial biofuels, and chemicals without further treatment.