Hydrothermal Upgrading (HTU) Process

The HTU process converts a large variety of biomass feedstocks into a liquid fuel that can be upgraded to a high quality diesel fuel. The HTU process heats the feedstock in water to 300-350 Celsius at 100-180 bars pressure for 5 to 20 minutes in order to facilitate the removal of oxygen. Typically, 85 percent of the oxygen is removed in equal parts of carbon dioxide and water (Goudriaan et al. 2005).

(Table:Typical HTU product distribution)

The biocrude readily separates from water and can be separated into light and heavy crude through extraction. The light crude is mineral-free and can be used for high-efficiency electricity production. For large-scale applications, the light crude is upgraded to produce a premium gasoil that has excellent ignition properties and can be blended directly with conventional diesel (Naber and Goudriaan 2003). There are no adaptations needed for engines to use this fuel. The heavy crude fraction is formed as a coal-like solid that can be co-combusted for power production. The heavy faction may also be gasified to produce ‘green hydrogen’ for use in catalytic hydrodeoxygenation.

The first commercial HTU plant demonstration is being conducted by Total France and NV Huisvuilcentrale Noord Holland. The capital investment for the plant is estimated at US$25 million. Currently, the HTU process can compete with premium diesel made from petroleum when crude prices are near US$50/barrel and biomass can be obtained for US$2.50/GJ. When the process is coupled in a bio-refinery concept with protein extraction, HDO upgrading, and gasification, the products that can be produced expand beyond the biocrude and energy production to include premium cattle fodder, green kerosene for aviation fuel, and naphtha feedstocks for chemical plants (Naber et al. 2004).