NOVELTY - Conversion of organic material to hydrocarbon products involves feeding the organic material and catalysts to a hydrothermal decomposition reactor, decomposing the organic material into gas, vapors and char in the hydrothermal decomposition reactor by fast catalytic hydrothermal method, separating the product into a heavy slurry of char and oil, vapors and gas, condensing the vapors, separating the vapors into an aqueous fraction and an hydrocarbon fraction, and recycling a portion of char slurry in cavitation chamber (2).    USE - Conversion of organic material to hydrocarbon products e.g. crude oil used as fuel for diesel engine.    ADVANTAGE - The method enables efficient conversion of organic material to higher-value hydrocarbon products with improved stability, yield, and quality, and reduced oxygen content, by fast catalytic hydrothermal method.    DETAILED DESCRIPTION - Conversion of organic material to hydrocarbon products involves feeding the organic material and catalysts to a hydrothermal decomposition reactor, operating the reactor at a temperature of 200-380 degrees C for a residence time of 1-60 minutes, decomposing the organic material into gas, vapors and char in the hydrothermal decomposition reactor using high-local energy transfer through a cavitational effect by fast catalytic hydrothermal method, separating the product into a heavy slurry of char and oil, vapors and gas, condensing the vapors, separating the vapors into an aqueous fraction and an hydrocarbon fraction, recycling a portion of the char slurry in cavitation chamber, and conveying the excess char out of decomposition reactor. INDEPENDENT CLAIMS are included for the following:    (1) fast hydrothermal decomposition apparatus, which consists of a system for convenient preparation of feed, a decomposition reactor comprising a cavitation device having sharply-increasing local temperature and decomposed organic material, an inlet for feeding the organic material into the cavitation device, a vapor condenser and separator, and a char conveyor for conveying the char away from the reactor; and    (2) apparatus for preparation of slurry, which consists of a solid-liquid mixer, a degassing system, and a vapor condenser.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of fast hydrothermal decomposition apparatus.    Recirculation pump (1)    Cavitation chamber (2)    Reactor drum (3)