Lignin-based carbon fiber toward sustainability: Opportunities and challenges

With the increasing world energy consumption and escalating environmental issues in recent decades, renewable and low-cost carbon fiber has attracted ever-increasing attention from various industry sectors. Since its first development in the 1960s, lignin-based carbon fiber has been a continued interest worldwide due to the low costs and abundance of lignin. Besides traditional pulping industries, producing carbon fibers is among the most attractive solutions for emerging cellulosic biorefineries to valorize lignin-containing byproduct streams. Despite the increasing demands, the commercial realization of lignin-based carbon fiber currently faces significant technical challenges. This chapter describes the background of carbon fiber and reviews previous approaches to developing lignin-based carbon fiber. The desired precursor characteristics are described and the most critical factor for enhancing the quality of carbon fiber is discussed. This chapter further describes several approaches the authors employed to develop lignin-based carbon fiber with enhanced structural orientation and improved tensile properties. Finally, future research directions are recommended to improve the commercial perspective of lignin-based carbon fiber.