This paper introduces an efficient and low-cost method for fabricating lightweight carbon aerogels (CAs) using lignin as a renewable and aromatic biopolymer. By adjusting the ZnCl₂/lignin ratio, the porosity of the CAs is controlled, leading to a tunable epsilon-negative response in the radio-frequency (RF) region. The intrinsic plasmonic state of the 3D carbon network enables this response, which is distinct from traditional periodic building blocks. The CAs exhibit a weakly and low-dispersion epsilon-negative response, with values ranging from ≈−1500 to −200. EM simulations and equivalent circuit analysis highlight the inductive characteristics of the CAs, which are crucial for their effective EM shielding performance. The study demonstrates the potential of lignin-derived CAs in creating lightweight, tunable EM metamaterials with broad applications in extreme conditions.This paper introduces an efficient and low-cost method for fabricating lightweight carbon aerogels (CAs) using lignin as a renewable and aromatic biopolymer. By adjusting the ZnCl₂/lignin ratio, the porosity of the CAs is controlled, leading to a tunable epsilon-negative response in the radio-frequency (RF) region. The intrinsic plasmonic state of the 3D carbon network enables this response, which is distinct from traditional periodic building blocks. The CAs exhibit a weakly and low-dispersion epsilon-negative response, with values ranging from ≈−1500 to −200. EM simulations and equivalent circuit analysis highlight the inductive characteristics of the CAs, which are crucial for their effective EM shielding performance. The study demonstrates the potential of lignin-derived CAs in creating lightweight, tunable EM metamaterials with broad applications in extreme conditions.