TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The liquid state fertilizer in step (C) has ammonia nitrogen content of 1000-1600 mg/L, Kjeldahl nitrogen content of 1100-2000 mg/L, total phosphorus content of 200-800 mg/L, and COD content of 25-75 g/L. The alkali liquor of step (F) has a solute of sodium hydroxide and solvent of drainage water of step (G).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The marsh gas in gas storage cabinet of step (C) is separated to separate out methane and carbon dioxide. It comprises 55-65% methane and 25-35% carbon dioxide. The marsh gas in gas storage cabinet is sent to molecular sieve dehydration tank for deep dehydration to make the water content in the marsh gas be reduced to less than 5 mg/L; and the gas is led to a separation tower to separate. The carbon dioxide is absorbed by polyethylene glycol dimethyl ether solution in the separation tower to release methane. The released methane is sent to a booster to boost the pressure of methane at 0.3 MPa and then sent to molecular sieve dewatering tank for deep dewatering. The dewatered methane water content is less than 0.2 mg/L. It is metered through a turbine meter and buffered through a buffer tank and enters a ZW type compressor to compress until 20-25 MPa; and the compressed methane is directly sent to methane steel bottle. The homogenizing pool is internally provided with heating coil having an inlet connected with water outlet of marsh gas boiler and outlet connected with water inlet of marsh boiler; and the temperature of the mixture in the homogenizing pool is controlled at 60-68 degrees C through hot water circulation in the heating coil. The anaerobic reactor in step (C) is a total mixed type anaerobic reactor, which is internally provided with a stirrer, where 24 hours continuous running is performed and stirring speed is 30-50 rpm. It is internally provided with a heating coil having inlet connected with water outlet of marsh gas boiler and outlet connected with water inlet of marsh gas boiler; and the sewage temperature in the anaerobic reactor is controlled at 55 plus minus 2 degrees C through hot water circulating in the heating coil, where hot water coil inlet is at 62 degrees C and hot water coil outlet is at 58 degrees C. The aerobic pool is internally provided with a heating pipe; and the marsh generated in step (C) is heated. The aerobic aeration of step (H) is conducted using an aeration pipe at the bottom of composting pool, where air is blasted from the bottom of the composting through an aeration machine. The autotrophic denitrification filler is used in step (E). It comprises sulfur and calcium carbonate at 1:10-10:1 weight ratio by sintering. The autotrophic denitrification filler is 3-15 vol.% of the total volume of denitrification pool.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The polyethylene glycol dimethyl ether solution absorbed with carbon dioxide is sent to flash tank at 0.05 MPa, where because pressure is reduced, the carbon dioxide is flashed out from polyethylene glycol dimethyl ether solution and filled in carbon dioxide storage tank through a voltage stabilizing valve and sent to crops greenhouse to serve as carbon dioxide gas fertilizer. The coagulant aid in flocculation dewatering of step (D) is non-ionic polyacrylamide, where sludge floc is dewatered by centrifugal dewatering machine through a rotating speed of 8000 rpm, total phosphorus content in the sewage sludge is 30-55 mg/L, ammonia nitrogen content is 500-1000 mg/L, chemical oxygen consumption amount is 4000-7000 mg/L, and water content of sludge after dewatering is 65-72%; and the sludge is led to step (H) through a spiral conveyor for aerobic composting.