Title : Waste-derived eggshell-based catalysts for sustainable valorization of tamarind seed waste into value-added bio-oil
Abstract:
The valorization of agro-industrial residues into value-added chemicals represents a sustainable approach to resource utilization and supports the transition toward a circular bioeconomy. In the present study, tamarind seed waste, an underutilized lignocellulosic biomass, was investigated as a renewable feedstock for bio-oil production through catalytic pyrolysis in a fixed-bed reactor. To enhance the yield and chemical quality of the bio-oil, waste-derived CaO-based catalysts, including calcined eggshells and mixed calcined CaO–MgO, were evaluated and systematically compared with commercial CaO under identical operating conditions. The catalysts were characterized using structural and thermal analytical techniques, which confirmed their high thermal stability, strong basicity, and favourable surface characteristics, making them suitable for catalytic cracking and deoxygenation reactions during biomass conversion. The presence of these catalysts significantly altered the distribution of pyrolysis products by promoting the conversion of heavy oxygenated compounds into lighter and more valuable oxygenates, thereby improving the overall quality of the liquid product. GC–MS analysis revealed a distinct shift in the bio-oil composition, with allyl alcohol emerging as the predominant compound, indicating efficient deoxygenation and selective upgrading of the pyrolysis vapours. Among the catalysts investigated, eggshell-derived CaO demonstrated promising catalytic performance while simultaneously providing an effective route for the valorization of food waste. The integration of tamarind seed waste and biogenic catalysts into a single thermochemical process highlights an environmentally benign and resource-efficient strategy for converting multiple waste streams into high-value platform chemicals. This approach not only reduces dependence on commercial catalysts but also contributes to waste minimization, renewable energy production, and sustainable chemical manufacturing. The findings demonstrate the potential of waste-derived inorganic catalysts for biomass valorization and underscore their significance in developing low-cost, eco-friendly catalytic technologies for future bioenergy and biorefinery applications.
