Hydrochar Production by Hydrothermal Carbonization: Microwave versus Supercritical Water Treatment

Abstract

Hydrochar, a carbonaceous material produced through hydrothermal carbonization of lignocellulosic biomass, has gained significant attention due to its versatile applications in agriculture, energy, and environmental protection. This review extensively explores hydrochar production by hydrothermal carbonization, specifically microwave and supercritical water treatment. These innovative approaches hold substantial promises in enhancing the efficiency and sustainability of hydrochar synthesis. The review commences with an in-depth analysis of the fundamental principles governing hydrochar production, emphasizing the distinct mechanisms of microwave and supercritical water treatment. Insightful discussions on the influence of critical process parameters, such as temperature, pressure, and residence time, underscore these factors’ pivotal role in tailoring hydrochar characteristics. Drawing on a wide array of research findings, the review evaluates the impact of different lignocellulosic biomass feedstocks on hydrochar properties, which is crucial for optimizing hydrochar production. The comparative assessment of microwave and supercritical water treatment sheds light on their unique advantages and challenges, guiding researchers toward informed decision-making in selection of methods. Furthermore, the review delves into the myriad applications of hydrochar, spanning soil amendment, carbon sequestration, and renewable energy. Environmental considerations and life cycle assessments associated with microwave and supercritical water treatment are also explored, providing a holistic perspective on the sustainability of hydrochar production. In conclusion, this comprehensive review synthesizes current knowledge on hydrochar production from diverse lignocellulosic biomass sources, emphasizing the efficacy of microwave and supercritical water methods.