Hydrothermal liquefaction process: Review and trends

The processing of biomass into biofuels has become an increasingly attractive option as a tool against climate change. One of the most relevant technologies is hydrothermal liquefaction, since it allows processing biomass with high water content without the need for prior drying, obtaining as a product a biocrude oil with high energy densification, lower density, and lower heteroatom content compared to other processes such as pyrolysis. In addition, its operating conditions are moderate, with pressure ranges of 100 to 200 bar and temperatures of 200 to 400 °C, which are much less drastic conditions than gasification and methanation, competing technologies in the transformation and valorization of biomasses for fuel production. Therefore, this article reviews the current state of research on the hydrothermal liquefaction process through of a bibliometric analysis with scientometric parameters that show the growing interest, the collaboration between countries, the evolution, and trends in research topics.