Supercritical fluid extraction (SCFE) can reduce sample preparation time, and recovery from the methods can be equal or better than that of the classical extraction techniques for solid and semi-solid samples. The properties of a supercritical fluid (SCF) can also improve extraction efficiency and speed. The process is based on the use of dual effect (extraction and entrainment) SCF solvents. Conversion by SCFE of biomass to liquids has been demonstrated with the use of a number of processing configurations. These different processing techniques tend to emphasize different mechanism subsets within the large group of potential chemical mechanisms by which biomass is converted to primary products and, thereafter, further converted by varying degrees to final products. SCFE with CO2 is an attractive alternative to conventional Soxhlet extractions using hazardous organic solvents. (C) 2000 Elsevier Science Ltd. All rights reserved.