Recent advances in the characterization and applications of biochar and hydrochar

• • Biochar produced via pyrolysis at >400 °C yields high porosity and thermal stability, enabling long-term CO2 sequestration and gas-phase applications; hydrochar from hydrothermal carbonization retains higher oxygen content and surface functional groups (carboxyl, hydroxyl, carbonyl), favoring aqueous-phase reactions and liquid adsorption. • • Comprehensive characterization using BET, SEM, XPS, XRD, and Raman spectroscopy is essential to link structural and chemical attributes to performance, confirming the potential of both materials for diverse environmental and technological challenges. • • Future development requires application-driven material design, integrating advanced analytics such as in situ characterization and machine learning to predict performance based on feedstock and production parameters, accelerating optimization cycles. • • Sustainable and scalable industrial deployment demands overcoming economic and logistical hurdles, developing robust energy-efficient production systems, and securing supply chains for diverse feedstocks, while exploring novel integrated biorefinery concepts and resource recovery (e.g., phosphorus from wastewater).