The complete use of biomass and also the efficient management of waste materials are big challenges that must be overcome in this century. The work presented in this article uses lignin extracted from rice husk, using the organosolv method, as a filler in the residual expanded polystyrene (PS) matrix to obtain a PS/lignin composite. Two different carboxylic diacids (adipic acid and itaconic acid) were also employed as aditives. The initial materials and solvent were mixed and exposed to a medium pressure UV radiation source. The concentration of the lignin content was varied to evaluate its effect on the final material. The material was characterised using UV-Vis, FTIR, EDS, MEV, GPC, and mechanical assays. The spectroscopic and chromatographic data showed that 10 min of exposure was enough to promote changes in the polymeric chain. Due to the new spectroscopic features, a photografting reaction occurred resulting in a stable PS/Lignin composite. Morphological analysis showed that even with a magnification of 40,000X some conditions result in films with great homogeneity. The mechanical tests showed a reduction in the tensile strength value with an increased lignin content, but in general, maintained the value of Young's modulus. Photochemical reactions were performed using a low complexity setup, in fast and mild reaction conditions, generating new uniform materials from polymeric residue and industrial waste. 1.