During the period 1982-1993, the Royal Dutch Shell Laboratory developed the HTU (Hydro-Thermal Upgrading) process to convert wet biomass such as wood, plants or organic waste into a liquid fuel, so-called biocrude. Biomass is firstly treated in an aqueous slurry at 200°C and 30 bar, followed by a treatment at 330°C and 200 bar. This process results in a biocrude, an oil with low oxygen content, which can be further upgraded by a catalytic hydrodeoxygenation step to a high-quality naphtha or diesel oil with very low oxygen, nitrogen and sulfur contents that can be blended in any ratio to fossil diesel [60, 61].