Metal recovery

Patent Granted PROBLEM TO BE SOLVED: To provide a method for producing formic acid by wet oxidation of biomass with which the biomass abundantly present in the natural world is converted into the formic acid in a high yield by utilizing actions of high-temperature and high-pressure water and the biomass can be converted into formic acid under relatively mild conditions as compared with the conventional water in the supercritical state without requiring an expensive noble metal catalyst etc., during the reaction with a result that the method is inexpensive with little load even on the environment because only the water is used as a reaction solvent.