Hydrothermal Carbonization of Industrial Sludge: Recent Advances, Challenges, and Perspectives

Industrial sludge is a ubiquitous by-product of various manufacturing processes, including wastewater treatment, food processing, pulp and paper production, and chemical synthesis. However, the disposal of industrial sludge presents significant environmental and economic challenges due to its high water content, organic content, and potentially hazardous contaminants. Therefore, the development of sustainable and cost-effective methods for industrial sludge treatment and disposal is crucial. Hydrothermal carbonization (HTC) is an emerging technology that shows promise for the treatment of industrial sludge. The HTC process involves heating the sludge at high temperatures (usually between 180 and 250 °C) and autogenous pressure under aqueous conditions. The organic compounds in the sludge undergo hydrolysis, dehydration, and condensation reactions during the process, leading to the formation of a solid product called hydrochar. HTC technology has several advantages for industrial sludge treatment, including the conversion of sludge into a valuable solid fuel, volume reduction, and environmental pollution mitigation. This chapter provides an overview of the principles and potential benefits of HTC technology applied to industrial sludge treatment. The chapter discusses the effects of key process parameters on HTC performance, such as pressure, temperature, residence time, and feedstock characteristics. Additionally, the current state of HTC technology applied to industrial sludge treatment is discussed and future research directions are highlighted. By converting industrial sludge into hydrochar, HTC technology offers a sustainable and efficient method for the treatment and management of industrial waste.