Abstract
The growing demand for renewable fuels has renewed interest in biodiesel production, prompting exploration beyond conventional reactors. This review assesses three-dimensional (3D) printed microreactors for biodiesel synthesis via transesterification, with a focus on their potential for enhanced process efficiency, sustainability, and modular deployment. Compared with conventional batch and stirred-tank reactors, 3D-printed microstructured systems often offer superior mass and heat transfer, enabling biodiesel yields up to similar to 99% in some studies, with critically short residence times (e.g., as low as similar to 5 s) and reported energy reductions of 60% to 90% under optimal conditions. Optimized configurations in recent work achieved energy requirements as low as similar to 0.05 to 0.12 kWh L-1, substantially lower than the typical 0.25 to 0.60 kWh L-1 for conventional setups. However, existing studies remain limited in number and scope: issues such as catalyst leaching, chemical and thermal stability of printing materials, dimensional inaccuracies, and scalability of microreactor networks remain under-investigated. Long-term durability, real-world feedstock variation (e.g., high-FFA waste oils), and comprehensive lifecycle assessments are often lacking, limiting confident extrapolation to industrial scale. Despite these challenges, the emerging evidence suggests significant promise for 3D-printed microreactors as a pathway toward modular, energy-efficient, and potentially low-carbon biodiesel production, provided that future work addresses their practical limitations and validates performance under industrially realistic conditions.