Boosting wet yeast-based biodiesel production by in-situ transesterification using a novel acid-base bifunctional carbon-based catalyst derived from spent coffee ground and cement residue

Production of yeast-based biodiesel using waste-derived catalyst correlates with the sustainable development concept. For this goal, a novel waste-derived acid-base bifunctional carbon-based catalyst, SCG@CR-SC, was generated from spent coffee ground and cement residue by wet impregnation and direct hydrothermal sulfonation, and their catalytic ability was evaluated for enhancing biodiesel production from SCO-rich wet cell of Rhodotorula sp. KKU-WP2 (SCO-RWP2) through wet in-situ transesterification (W-ISTE). The SCG@CR-SC characteristic underwent comprehensive analysis through FE-SEM-EDX, FTIR, XRD, Raman, and TGA techniques, confirming the successful introduction of CaO and sulfonic (–SO3H) groups on the SCG@CR-SC surface. SCG@CR-SC exhibited good catalytic efficiency for producing SCO-RWP2-biodiesel under optimized W-ISTE conditions (3.0 wt% catalyst amount, 15:1 MeOH/SCO-RWP2 ratio, 65 °C for 1.0 h), reaching 96.9 % (1st cycle), 89.9 % (4th cycle) and >93 % (regenerated catalyst) of FAME conversion yield, surpassing results reported for similar studies. Notably, the estimated fuel properties of SCO-RWP2-biodiesel were correlated well with the requirements for ASTM D6751 and EN 14,214 international standards, representing great application prospects. The findings underscore the potential of using SCO-RWP2 as a promising feedstock and SCG@CR-SC as an eco-friendly catalyst for boosting biodiesel production, that might mitigate environmental concerns and promote the sustainable development of clean and renewable energy.