Adsorption

Composite number

Engineering

Sewage treatment

Pyrolysis

Materials science

Raw material

Sewage sludge

Cellulose

Hydrothermal liquefaction

Carbon fibers

Chemical engineering

Geology

Coal

Oceanography

Waste management

Organic chemistry

Hydrothermal circulation

Biofuel

Biomass (ecology)

Carbonization

Combustion

Aqueous solution

Process engineering

Environmental science

Composite material

Chemistry

Pulp and paper industry

Solid fuel

Hydrothermal carbonization

Fuel

HydroThermal Carbonization (HTC) is a thermochemical process by which biomass is treated in aqueous environment under temperatures of 180–300 °C and self-generated pressure to produce solid fuel as hydrochar from wide range of organic wastes such as garbage, bio solids, agro residues and organic wastes from industrial operations. It is an economically efficient process as it eliminates the need for pre-drying and generates energy rich carbonaceous products. This paper reviews the hydrochar formation mechanisms of hydrolysis, dehydration, decarboxylation, condensation, polymerization and aromatization in terms of the critical hydrothermal parameters such as temperature, residence time, solid load, pressure, pH and aqueous conditions to derive fundamental understanding in the improvements required in HTC process design for waste to energy conversion. The identification of design protocols of HTC for solid fuel production is expected to expedite further research and field level scale up of this technology.

Hydrothermal carbonization of organic wastes to carbonaceous solid fuel – A review of mechanisms and process parameters