Lignin as a flame retardant for biopolymers

Very recently, China and India as the game changers of the world producing million tons of greenhouse gases have promised to invest up to 35% of their gross domestic product on global climate change before 2030. In line with such green policies, but starting more than 3 decades ago, research centers active in the field of materials sciences and engineering and those working on the development of flame retardants for polymers have been advised by the governments to switch from halogen-based to sustainable flame retardants. Bio-based flame retardants rapidly proved obvious candidates for this purpose, but to display adequate flame retardancy, they require physical and/or chemical modification. Lignin is a versatile biodegradable polymer, which has been widely applied as a part of flame retardant systems in polymers. There is a plethoric number of works on lignin-based flame retardants and flame retardancy of lignin-incorporated polymer systems. This chapter aims at reporting and classifying these works on flame retardancy of unmodified and modified lignin and its "sister", i.e., nanolignin, as flame retardant additives for polymer systems.