OVERVIEW: Supercritical water is a great medium in which to perform chemical reactions and to develop processes. Due to its unique thermo-physico-chemical properties, supercritical water is able to play the role of solvent of organic compounds and/or to react with them. These specific properties have been used since the 1990s to develop new technologies dedicated to the environment and energy. IMPACT: Supercritical water based technologies are innovative and efficient processes having a strong impact on society, the environment and the economy, and is termed a sustainable technology. APPLICATIONS: Three main applications for supercritical water technology are under development: (i) supercritical water oxidation (SCWO); (ii) supercritical water biomass gasification (SCBG); and (iii) hydrolysis of polymers in supercritical water (HPSCW) for composites/plastics recycling. In this paper some fundamentals of supercritical water are first presented to introduce the above three major developments. Then these technologies are reviewed in terms of their present and future industrial development and their impact on the environment and on energy production. (C) 2010 Society of Chemical Industry