Valorization of seaweed industrial by-products as potentially sustainable activated carbon precursors: Production routes, preparation, and characterization

The growth of the global seaweed industry has led to the generation of substantial by-products, which, if not properly managed, can damage the environment. Simultaneously, the rising demand for activated carbon (AC) highlights the need for sustainable AC precursors. Hence, this study examined the potential of valorizing by-products from agar and carrageenan production as AC precursors. This study investigated in detail the by-product production routes, preparation steps, and characterization. The production routes encompassed material flow, mass balance, and the equipment employed, while by-products obtained from the initial cleaning, filtration, and milling processes were selected for subsequent valorization. The preparation process for valorizing each by-product was outlined. Subsequently, the physical and chemical properties, surface morphology, elemental composition, and thermal stability of the prepared by-products as AC precursors were characterized. In the production route for processing 1000 kg of raw seaweed as feedstock (Eucheuma cottonii for carrageenan and Gracilaria sp. for agar production), the filtration process using membrane filter press equipment produced the highest amount of by-products, which is approximately 472.39 kg from carrageenan and 493.39 kg from agar production. Furthermore, washing, drying, grinding, and sieving were required to valorize the by-products as AC precursors. Ultimately, the by-products valorized from the initial cleaning process of agar production have the highest potential to serve as sustainable AC precursors, as evidenced by their high organic matter and carbon content. This study provides an industrially grounded assessment of valorizing seaweed industrial by-products as AC precursors, which offers a foundation for future AC synthesis and applications.