Advancements and environmental impact of hydrothermal processing of algal biomass

Over the past 10 years, there has been a growing interest in the field of hydrothermal processing of algal biomass. By making use of a thermochemical process, biomass can be transformed into char, biocrude, and other useful compounds. Because hydrothermal technologies are economical and environmentally benign and provide high-quality products, they are becoming more and more popular among thermochemical techniques. Examples of these technologies are hydrothermal carbonisation, liquefaction, and gasification. Different kinds of wet biomass are converted using hydrothermal technology into products with added value including syngas, bio-oil, and hydrochar. Because the biomass is treated wet in hot-compressed water as slurry, this method has been found to be particularly suitable for high-moisture aquatic biomass, such as macro- and microalgae. This article has provided an overview of the several methods for harvesting algae and the variables that impact its growth. The role of algae in hydrothermal processing and the mechanism of hydrothermal processing of algal biomass are put forward in this investigation in order to systematically grasp the current situation and create a basis for promoting the technology. This content has also emphasised the factors that affect the hydrothermal process, and the discussion has also been directed towards the diverse uses of hydrochar derived from algal biomass, including solid biofuel, adsorbent, carbon sequestration, nutrient retention, and supercapacitor applications. In order to achieve a comprehensive environmental profile, the life cycle assessment (LCA) concludes by discussing the limitations of the state of the art as well as the introduction of new possible input categories. The LCA of hydrothermal biomass conversion and hydrothermal technologies are the subjects of this comprehensive study.