Agricultural Residue Derived Solid Acid Catalyst: Tomato Stalk Biochar for Biodiesel Production

Abstract

The escalating demand for sustainable and carbon-neutral energy sources has intensified research into biodiesel production from renewable feedstocks using environmentally friendly catalysts. This study presents the synthesis and application of a low-cost solid acid catalyst derived from tomato stalk, a widely available agricultural waste, for biodiesel production from microalgal oil. The catalyst was prepared via carbonization and subsequent sulfonation, and its physicochemical characteristics were thoroughly evaluated. The highest sulfonic acid density was achieved at a carbonization temperature of 500 degrees C and sulfonation at 100 degrees C for 5 h. Under the conditions of 9:1 methanol/oil molar ratio, 5 wt% catalyst and 60 min resulted with a biodiesel yield of 93%. Statistical analysis confirmed the significant influence of carbonization parameters on catalytic efficiency. Compared to conventional homogeneous acid catalysts, produced biochar based solid acid catalyst offers a greener and reusable alternative for biodiesel synthesis. Moreover, the valorization of tomato stalk waste into high-performance catalysts aligns with circular bioeconomy principles, addressing both agricultural waste management and renewable fuel production. This work shows a promising route toward overcoming key economic and ecological barriers in biofuel technology, thereby contributing to the broader transition toward sustainable energy systems.