Advancements in ZSM-5 Catalytic Torrefaction of Microalga Chlorella sp. for Biochar Production

With the growing studies on microalgae as a sustainable source of biomass and other high-value products, the demand for microalgal biomass has increased. Hence, microalgae waste accumulation has become a growing environmental issue, threatening marine ecosystems and water quality. Torrefaction is a promising method for converting this waste into a solid product called biochar, contributing to carbon capture and reducing greenhouse gas emissions. Inert and oxidative torrefaction have become the primary methods, but both often require high energy and long processing times. Catalysts offer a pathway to improve these limitations by enhancing carbon retention and promoting deoxygenation and decarboxylation reactions. This study utilizes zeolite ZSM-5 as a catalyst for biochar production derived from microalga Chlorella sp. under inert and oxidative conditions. The main objective is to investigate the effects of torrefaction parameters and zeolite on the solid yield, higher heating value, and carbon content of the raw and torrefied microalgae. Results show that ZSM-5 can effectively increase the carbon content up to 58.21 %, and achieve an HHV of 25.82 MJ·kg-1. Comparison with existing literature confirms that catalytic torrefaction improves energy content and shifts biochar properties closer to those of fossil fuels such as lignite and coal. These findings demonstrate the potential of catalytic torrefaction as a sustainable strategy for microalgal waste management and solid biofuel production. Future work will focus on the analysis and characterization of liquid and gaseous byproducts to further elucidate the catalyst’s role in reaction pathways and overall system efficiency.