The HyVent hydrothermal process is about the oxidation of dissolved or suspended components in water using an oxidizer. The oxidation reactions occur in superheated water at a temperature above the normal boiling point of water (100° C).

The system is kept under pressure to avoid evaporation of water. The energy consumption is controlled by avoiding the supply of heat for latent heat of vaporization. Liquid water is necessary for most of the oxidation reactions to occur. Compounds oxidize under these conditions that would not oxidize under dry conditions at the same temperature and pressure.