NOVELTY - Method for processing digestive liquid (16), involves (a) performing methane fermentation of organic waste (10) in digestive liquid storage tank (301), (b) storing phosphoric acid containing water (19), (c) adding magnesium compound (20) to the phosphoric acid containing water, (d) reducing pressure in the digestive liquid storage tank, (e) introducing ammonia gas (18) emitted from the digestive liquid into phosphoric acid containing water, and (f) precipitating and collecting magnesium ammonium phosphate in the phosphoric acid containing water.    USE - The method is useful for processing digestive liquid.    ADVANTAGE - The method consumes less energy, is cost-effective and environmentally-friendly, and utilizes recovery substances as highly advanced fertilizer.    DETAILED DESCRIPTION - Method for processing digestive liquid (16), involves (a) carrying out methane fermentation of organic waste (10) in digestive liquid storage tank (301) and storing the digestive liquid generated by the fermentation, (b) storing phosphoric acid containing water (19) supplied from outside of phosphoric acid containing water storage tank (302), (c) adding magnesium compound (20) to the phosphoric acid containing water stored in the phosphoric acid containing water storage tank, (d) reducing pressure in the digestive liquid storage tank connected with the phosphoric acid containing water storage tank by gas flow path, (e) introducing ammonia gas (18) emitted from the digestive liquid in the digestive liquid storage tank into the phosphoric acid containing water storage tank by gas flow path and contacting the gas with the phosphoric acid containing water, (f) precipitating magnesium ammonium phosphate in the phosphoric acid containing water, and (g) collecting the precipitated magnesium ammonium phosphate. INDEPENDENT CLAIMS are included for the following:    (1) method for processing organic waste, involves adding dilution water (12) to organic waste to obtain slurry, performing methane fermentation of the slurry, performing the above-cited steps (a)-(g), removing suspended solid from the residual digestive liquid (23) in which the ammonia gas is removed and remains in digestive liquid storage tank, neutralizing the residual digestive liquid, and using the neutralized residual digestive liquid as dilution water;    (2) apparatus for processing digestive liquid (300), comprises digestive liquid storage tank for storing the digestive liquid, phosphoric acid containing water storage tank for storing the phosphoric acid containing water and storage tank pressure reduction unit (303) for reducing pressure by sucking internal gas (21) of the phosphoric acid containing water storage tank; and    (3) apparatus for processing organic waste, comprises preprocessor (100) for adding dilution water to organic waste, methane fermentation apparatus (200) for carrying out methane fermentation of organic waste, digestive liquid storage tank, phosphoric acid containing water storage tank, storage tank pressure reduction unit and residual digestive liquid adjusting device (400).    DESCRIPTION OF DRAWING(S) - The drawing shows flowchart of organic waste processing method and organic waste processing apparatus.    Organic waste (10)    Dilution water (12)    Digestive liquid (16)    Ammonia gas (18)    Phosphoric acid containing water (19)    Magnesium compound (20)    Internal gas (21)    Residual digestive liquid (23)    Preprocessor (100)    Methane fermentation apparatus (200)    Apparatus for processing digestive liquid (300)    Digestive liquid storage tank (301)    Phosphoric acid containing water storage tank (302)    Storage tank pressure reduction unit (303)    Residual digestive liquid adjusting device (400)