Biomass Wastes Hydrothermal Carbonization: A Mini-Review on Hydrochar Properties and Combustion Performance

Abstract

Hydrothermal carbonization (HTC) is one of the thermochemical processes commonly used to convert raw biomass into hydrochar, a valuable solid carbonaceous product. Waste biomasses such as forestry residues, agricultural wastes and sewage sludges have drawn considerable interests as hydrochar feedstocks. These materials are regarded as economically sustainable material and their usage provides an effective solution to waste management concerns. The carbonization procedure is accomplished using water as a reaction medium at temperatures between 150 and 300 °C and pressure up to 20 bar. Typically, the biomass transformation process is completed using a carbonization time ranging from several minutes to several hours. In addition to the HTC temperature and carbonization time, the impact of biomass feedstocks utilized on the hydrochar properties and fuel/combustion performance dictated their potential applications as solid fuel and carbon materials. This paper provides a brief commentary on recent studies involving the main biomass wastes transformation using the HTC approach. The impact of raw biomass quality on the resulting hydrochar properties is highlighted and combustion behaviour/performance are compared and discussed.