NOVELTY - Environment-friendly system for processing sludge and preparing fertilizer comprises a sludge biogas digester (2), a fertilizer producing machine (4), a purification separator (7) and a steam generator (9). One end of the sludge biogas digester is connected with a sludge inlet pipe (1). The lower end of a sedimentation tube is connected to the fertilizer producing machine and the top through a biogas pipeline. A pump is respectively connected to the lower part of multiple purification separators. The top of the separator has a methane guide tube and is connected to the steam generator.    USE - The system is useful for processing sludge and preparing fertilizer.    ADVANTAGE - The system mixes and digests the sludge containing high organic content, which is easy to decompose; does not dehydrate the moisture content and produces biogas in the biogas digester; utilizes different gases to purify the material to decompose methane and carbon dioxide, and conveys methane for power generation and carbon dioxide for producing fertilizer; and completely utilizes the resources, thus meeting the national requirement of environment protection.    DETAILED DESCRIPTION - Environment-friendly system for processing sludge and preparing fertilizer comprises a sludge biogas digester (2), a fertilizer producing machine (4), a purification separator (7) and a steam generator (9). One end of the sludge biogas digester is connected with a sludge inlet pipe (1). The lower end of a sedimentation tube is connected to the fertilizer producing machine and the top through a biogas pipeline. A pump is respectively connected to the lower part of multiple purification separators. The top of the separator has a methane guide tube and is connected to the steam generator. The guide tube is connected to a transformer to supply electricity. The purification separator is connected with a carbon dioxide gas outlet pipe. The bottom of the purification separator is equipped with a recycling pipe and is connected to the biogas pipeline for further purification and separation.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the environment-friendly system for processing sludge and preparing fertilizer.    Sludge inlet pipe (1)    Sludge biogas digester (2)    Fertilizer producing machine (4)    Purification separator (7)    Steam generator (9)