Hydochar and biochar: Production, physicochemical properties and techno-economic analysis

Utilization of natural, abundant, and renewable resources for the production of carbon materials with simple and energy-efficient processes is an upsurge interest. The production processes and resultant biochar can address widespread concerns such as climate change, energy crisis, and environmental pollution. The properties of produced chars (biochar/hydrochar) depend on the production methods, feedstock, and operating parameters, which significantly affect their use for various applications. In this review, production, physiochemical properties, and techno-economic analysis of chars are summarized. This review provides the fundamentals and reaction mechanism of char production methodologies. Physicochemical properties based on chemical composition, functional groups, structure, porosity, and shapes have been compared. The effects of operating parameters on the physicochemical properties of chars are discussed. In addition, this review offers insights on new directions for char production and research in the future, based on the updated and detailed investigation of energy balance with economy of char production methodologies.