TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalysts are oxides and hydroxides of metal in group-I and group-II of periodical system, or aluminosilicate compounds. The oxides and hydroxides of metal are preferably sodium hydroxide, potassium hydroxide, calcium hydroxide, or calcium oxide. The aluminosilicate compound is synthetic or natural zeolite.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Property: The residence time of decomposition reactor is preferably 5-30 minutes. Preferred Components: The mechanical device is a pump. The mixer is a horizontal mixer.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Property: The boiling point of heavy oil is more than 280 degrees C. Preferred Process: Conversion of organic material to hydrocarbon products further involves subjecting organic material in the hydrothermal decomposition apparatus to high-local energy transfer through the cavitational effect, providing cavitational energy with respect to cavitation chamber using mechanical devices or ultrasounds transducers, diffusing decomposition vapors into the condenser and performing condensation process, conveying a portion of char in the form of fine particles from the reactor, conveying slurry in a stagnant zone containing particles capable of separating from heavy organic liquids, recycling heavy liquids in the decomposition reactor, and condensing vapors and passing condensed vapors to the entrance of cavitation chamber. The hydrothermal decomposition is enhanced by adding water at the entrance of cavitation chamber. The heat for decomposition process is provided directly inside the reacting mixture, without using solid exchange surfaces. The slurry is obtained by adding hot-recycled organic heavy oil to the pre-charged solids containing organic material and catalysts. Preferred Components: The organic material is plant biomass, bio-renewable fats and oils, animal biomass, organic municipal waste, sewage sludge, plastics, and/or petrochemical-based waste feedstock. The solid particles remain suspended in the heavy oil. The heavy oil is a mineral oil.