Advances and challenges on hydrothermal processes for biomass conversion: Feedstock flexibility, products, and modeling approaches

Developing technologies to harness biomass energy is essential for the transition to a low-carbon economy. Emerging biorefineries, where biomass energy is converted via thermochemical processes like Hydrothermal Liquefaction (HTL), could be at the core of this transition. This review offers a comprehensive analysis of biomass Hydrothermal Processes (HTP), emphasizing HTL as a sustainable approach to convert high-moisture, heterogeneous biomass—including municipal solid waste, lignocellulosic residues, and microalgae—into biofuels and valuable bioproducts. This review examines the flexibility of feedstocks suitable for hydrothermal processes, including organic solid waste, food waste, and sludge, while critically assessing recent advances in reactor design, as well as kinetic and phenomenological modeling. Additionally, to the best of our knowledge, this work proposes the first strategies to model and simulate transport phenomena within HTL technology, capturing the structural effects generated by the chemical reactions involved. The analysis identifies existing challenges in understanding these processes, highlights research gaps, and proposes a roadmap for future studies. ... mehrThis roadmap integrates theoretical and experimental approaches aimed at accelerating the development of next-generation biorefineries and supporting the shift towards a circular bioeconomy.