​In response to the energy crisis and the need for carbon neutrality,developing green heterogeneous catalysts for converting wastevegetable oils into biodiesel is promising for reducing carbon emissionand pollution. This study introduces a novel sulphonated lignin-basedcarbon aerogel catalyst, synthesised through a sol-gel process to form alignin-based hydrogel, followed by solvent exchange, supercritical CO₂drying, carbonisation at 400°C in an N₂ atmosphere and sulphonationwith sulphuric acid. The catalyst, LCA-S1:10(10), features ananostructured morphology with a high specific surface area of 78.16m²/g and a strong -SO₃H acidic intensity of 2.81 mmol g−1. ResponseSurface Methodology (RSM) was used to optimise reaction conditions,employing a central composite rotatable design (CCRD) with a two-factor, five-level approach. Optimal conditions included 10 wt% catalystloading, an oil-to-methanol molar ratio of 1:45, a reaction temperatureof 65°C, and a reaction time of 5 hours, achieving a maximum biodieselconversion of 91.3%. The biodiesel produced met ASTM D6751 and EN14214 standards, highlighting its potential for broader application​​