THERMOCHEMICAL CONVERSION OF AGROWASTE BIOMASS INTO BIOCHAR FUEL: A REVIEW ON PYROLYSIS AND TORREFACTION

Abstract

The continuous growth of the global population, urbanization and industrialization has led to a steep increase in worldwide energy demand, exerting immense pressure on conventional fossil fuel reserves. Fossil fuels currently dominate the global energy mix but are associated with severe environmental challenges such as greenhouse gas emissions, global warming and air pollution, highlighting the urgent need to explore sustainable and alternative energy sources. In response, renewable and sustainable energy resources have emerged as viable alternatives. Among these, biomass stands out as an abundant, carbon-neutral and renewable resource capable of producing valuable biofuels and bio-products. This review focuses on biomass availability, classification, composition, conversion pathways and the role of torrefaction and pyrolysis in producing energy-dense solid fuel biochar. The physicochemical characterization of biochar, its testing standards and its comparative performance with coal are discussed in detail. The paper further explores the applications of torrefied biomass, including its use as a co-firing agent in thermal power plants, feedstock for gasification and briquetting and a sustainable substitute for fossil coal in industrial and domestic heating. Moreover, the challenges and opportunities in biomass valorization are analyzed, emphasizing emerging opportunities in circular economy integration and decentralized energy systems. The study also identifies research gaps, particularly in optimizing process parameters for consistent biochar quality, developing cost-efficient torrefaction technologies and establishing standardized testing and classification methods. Overall, this review highlights the importance of optimizing thermochemical conversion processes to improve biochar yield and quality, contributing to clean, sustainable and circular bioenergy systems.