Concentrated Seawater‐Assisted Greener Production of Biochar: Waste Valorization and Its Implication in Circular Economy

Converting waste biomass into functional biochar offers a promising approach to carbon sequestration, but a sustainable manufacturing method is yet to be developed. The current work demonstrates the proof of concept of biochar production using concentrated seawater, a by‐product from seawater desalination, as the templating agent. The resulting biochar shows mixed meso‐ and micropores, high specific surface area and low oxygen content. Owing to these features, the biochar demonstrates applications as a modest methylene blue adsorbent (adsorption capacity up to 8.2 mg/g), satisfactory supercapacitor electrode (specific capacitance up to 135 F g −1 ), and superior CO 2 adsorbent (maximum capacity 4.05 mmol g −1 ). Moreover, we propose that the biochar production can be combined with other established processes for implementing circular economy to achieve concentrated seawater valorization, carbon sequestration and waste minimization.