Enhancing biomass gasification performance through microwave pretreatment: A comparative study on tar reduction, syngas quality, and process efficiency

The gasification of biomass presents a viable pathway for renewable energy production; however, challenges such as high tar content and low energy efficiency remain significant barriers. This study investigates the impact of microwave pretreatment on the gasification performance of sugarcane bagasse pellets in a 25 kWth downdraft fixed-bed gasifier, focusing on syngas quality, cold gas efficiency (CGE), and tar content, and comparing these parameters to untreated bagasse pellets of various sizes (6, 8, 10 mm), wood pellets, and beech wood chips. Results show that microwave pretreatment significantly alters the physicochemical properties of bagasse, reducing volatile matter from 74.48% to 38.03% and oxygen content from 49.2% to 29.0%, thereby increasing fixed carbon content and improving reactivity. This modification led to a remarkable reduction in tar content from over 2500 mg/Nm 3 to values as low as 71175 mg/Nm 3 and a more stable syngas lower heating value (2.78–2.84 MJ/Nm 3 ). Cold gas efficiency increased dramatically from approximately 27% to 58%, outperforming all untreated feedstocks. Additionally, microwave pretreatment shifted the pyrolysis zone closer to the oxidation zone, promoting better heat transfer and in-situ secondary tar cracking. Compared to wood-based feedstocks, bagasse especially when pretreated demonstrated superior tar suppression and greater process stability. These findings highlight microwave pretreatment as a highly effective strategy for improving syngas quality, reducing operational challenges, and advancing the feasibility of biomass gasification for clean energy applications.