NOVELTY - Method (M1) for treating biological waste for preparation of fertilizers, comprises: (a) mixing biological waste with a dilute sulfuric acid in a predetermined ratio; (b) filtering the mixture to obtain an organic slurry and an acidic liquid; (c) thermally cracking the organic slurry at an elevated temperature to obtain at least one of an ammonia gas, at least one fuel gas, and char and ash; (d) passing the ammonia gas through the acidic liquid and at least one of an organic slurry washing liquid, a char and ash washing liquid, and a suspension liquid; and (e) drying the mixture.    USE - The method is useful for treating biological waste for preparation of fertilizers (claimed), where the biological waste is manure, leftover food, slaughter remains, decomposed plants, and organic waste.    ADVANTAGE - The method: provides fertilizers without producing foul odors and combustive gases; is capable of extracting large percentage of nutrients from the biological wastes; is economical; utilizes lesser duration as compared to method of composting of the biological waste; and utilizes every bi-product produced in the process.    DETAILED DESCRIPTION - Method (M1) for treating biological waste for preparation of fertilizers, comprises: (a) mixing the biological waste with a dilute sulfuric acid in a predetermined ratio; (b) filtering the mixture of the biological waste and the dilute sulfuric acid to obtain an organic slurry and an acidic liquid; (c) thermally cracking the organic slurry at an elevated temperature to obtain at least one of an ammonia gas, at least one fuel gas, and char and ash, where the ammonia gas, the acidic liquid and the char and ash are used for preparation of the fertilizers; (d) passing the ammonia gas through the acidic liquid and at least one of an organic slurry washing liquid, a char and ash washing liquid, and a suspension liquid, where the organic slurry washing liquid is obtained by washing the organic slurry with water, the char and ash washing liquid is obtained by washing the char and ash with a washing liquid, and the suspension liquid comprises water and lime; and (e) drying the mixture of the acidic liquid and at least one of the organic slurry washing liquid, the char and ash washing liquid, and the suspension liquid to obtain a powder, where the powder is used as a fertilizer. An INDEPENDENT CLAIM is also included for a method (M2) for treating biological waste for preparation of fertilizers, comprising: the steps (a) and (b) as above per se; and thermally cracking the organic slurry at an elevated temperature to obtain a char and an ash, and at least one of an ammonia gas and at least one fuel gas; washing the char and ash with a washing liquid, where the washing liquid comprises water and sulfuric acid.