From biomass to biocrude: Innovations in hydrothermal liquefaction and upgrading

[Display omitted] •Hydrothermal liquefaction (HTL) is a key technology to process all biomass/wastes.•Biomass HTL yielded 60–86% biocrude, showed promise alternative to fossil fuels.•HTL recent advancements: catalyst effects, scalability and upgrading are reviewed.•Machine learning tools showed promising to optimize HTL operating parameters.•Continuous HTL and aqueous phase recycling showed potential for commercialization. It is crucial to find sustainable and renewable fuel sources because traditional fossil fuels are running out and pollution levels are rising. In this context, biocrude derived from biomass emerges as a promising alternative, with hydrothermal liquefaction (HTL) playing a pivotal role in this transformation. HTL's versatility in converting a wide range of biomass or waste materials into biocrude is especially notable. Therefore, this comprehensive review focused on the latest advancements in HTL technology, including its potential to process various biomass and waste materials, resulting in high biocrude yields (up to 60–86% from different biomass types). The study explored the latest advancements in HTL such as effects of catalysts in HTL processes, the scalability of the technology, and the potential for commercializing continuous HTL with aqueous phase recycling. It also explored the integration of machine learning for HTL optimization, offering insights into how these advanced computational techniques can enhance process efficiency and output quality. HTL and subsequent hydrotreatment emerge as key technologies for utilizing biomass as a renewable fuel source. This review not only highlights the current state of biocrude refining and upgrading technologies but also stresses the need for ongoing development in these domains. It presented HTL as a transformative solution in the energy sector, offering a sustainable fossil fuel alternative while tackling biocrude impurities and heteroatoms management challenges. The review concluded by underscoring the practical implications of HTL advancements, suggesting a roadmap for future research and development in this field.