Lignin derived carbon fiber and nanofiber: Manufacturing and applications

Concerns over unsustainable technology-driven economies, environmental threats, and the continuous reduction of petroleum feedstocks have stimulated research in green, biodegradable, and naturally available resources. Within this context, lignin is considered one of the promising alternatives for producing sustainable materials, as it is the second most abundant material in Nature after cellulose and has a unique and versatile structure. Despite being highly abundant, lignin has not found a place in economic policies and is often considered an unutilized waste product. In recent years, extensive efforts have been made to develop lignin as an active precursor for carbon fiber (CF) production. CF is typically produced from expensive and unsustainable polyacrylonitrile (PAN) precursors, and lignin offers a low-cost and environmentally friendly alternative. This review provides a detailed insight into the manufacturing process and applications of lignin-derived carbon fiber (CF) and carbon nanofiber (CNF). It also highlights the major challenges that lie ahead for the industrialization of lignin as an established CF precursor. While lignin has yet to effectively penetrate the CF market, standardizing its product, conducting well-organized cost analyses at various stages of production, and developing low-cost processing techniques could pave the way for wider adoption of carbon-based materials."