This chapter explores how lignin’s complex organic polymer structure can be integrated into thermoelectric materials to enhance their performance. Also, this chapter covers how the unique composition of lignin can be exploited in tuning electrical and thermal conductivity and, in turn, enhance thermoelectric efficiency using methods such as doping, nanostructuring, or composite formation. It also sheds light on lignin’s contributions to improving carrier mobility, thermal stability, and sustainability, developing a clearer understanding of how lignin-based materials could support the advancement of more efficient and eco-friendly thermoelectric technologies. This chapter highlights lignin’s potential in converting low-grade waste heat into usable energy, with attention to environmental and cost considerations. Additionally, it specifically covers recent developments in lignin-derived ionic conducting membranes, hydrogels, solar-driven thermoelectric generation, and the functionalization of carbon nanotubes with lignin biopolymers, as well as a model for ionic conducting membranes.