Engineering properties of hydrochar fabricated from hydrothermal carbonization of lignocellulosic biomass: Practice as adsorbent and catalyst in water treatment

The conversion of waste biomass into value-added products, energy, and materials is a key strategy for establishing a circular bio-economy and achieving sustainable technological development. Among various waste valorization techniques, hydrothermal carbonization (HTC) has emerged as a promising method due to its distinct advantages, including high efficiency and versatility in processing both lignocellulosic and non-lignocellulosic biomass. HTC enables the transformation of biomass into hydrochar , a carbonaceous material with significant potential in energy production, biofuels, and environmental remediation. This review highlights the optimization of HTC processes and strategies for enhancing hydrochar's engineering properties through surface functionalization . Special emphasis is given to the fabrication of adsorbents and catalysts from hydrothermal carbon, enabling the effective removal of emerging contaminants such as dyes, pesticides, pharmaceutical compounds, and heavy metals. Additionally, the modification of HTC carbon into fine and granular forms maximizes its adsorption and catalytic efficiency. The utilization of pelletized HTC carbon as a solid fuel and soil amendment further underscores its environmental and economic significance. With its unique properties—oxygenated functional groups, high surface area, hydrophobic nature, and conductivity—HTC carbon can be further enhanced through nanomaterial functionalization and composite support matrices, broadening its applicability in sustainable waste management and resource recovery. • Biomass-to-hydrochar conversion via hydrothermal carbonization (HTC) reviewed • Includes process optimization and surface functionalization of HTC-derived carbon • Detailed the adsorptive and catalytic degradation of contaminants using HTC • The importance of fabricating HTC as fine and granular particles is highlighted. • Hydrochar is versatile for various environmental remediation applications.