TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Device: In the mixture precipitating device, one side of the biogas slurry waste heat conducting tank is in contact with the mixing tank by the heat conducting device; the heat conducting device includes a cooling metal plate and a cooling angle iron, two sides of the cooling metal plate are respectively in contact with the biogas slurry waste heat conducting tank and the mixing tank, and one side of the cooling metal plate adjacent to the mixing tank is provided with multiple cooling angle irons. Two ends of the cooling metal plate are fixedly connected with the sides of the biogas slurry waste heat conducting tank via fixed expansion bolts, and the cement is poured into fixed connections between the cooling metal plate and the biogas slurry waste heat conducting tank at second time. A left side of the mixing tank is communicated with the precipitating tanks, an upper side is communicated with grit chamber via a sewage grid, and a lower side is in contact with the biogas slurry waste heat conducting tank via the cooling metal plate; the upper and lower sides at the bottom of the mixing tank are provided with cross inclined bases, a part at the bottom of the mixing tank adjacent to the fermentation tank is provided with a feeding pump, a middle part at the top of the mixing tank is provided with the mixing blender, and the feeding pump, a central shaft line of the mixing blender and a central shaft line of the mixing tank are overlapped; the upper and lower sides at the bottom of the precipitating tank are provided with transverse inclined bases, a left side at the bottom of the outmost precipitating tank is further provided with a vertical inclined base, and the upper and lower ends of the vertical inclined base are connected with the transverse inclined bases; the middle parts at the bottom of the separation walls are provided with one way valves, and the middle shaft lines of the one way valves are overlapped with the shaft line of the mixing tank. The top parts of the mixing tank and the biogas waste heat conducting tank are covered with the same transparent glass cover or glass house. Three precipitating tanks are provided. The biogas waste heat conducting tank is arranged inside the mixing tank or revolved around an outer part of the mixing tank. Preferred Method: In using mixture precipitating device for heating by waste, the fermentation solutions in the mixing tank are respectively 10 degrees C and 30 degrees C before and after conducting heat quantity of the heat conducting device, and the hot biogas slurry is 53 degrees C. In (c), the biogas slurry and biogas residues are obtained after solid-liquid separation, the biogas slurry is drained into the biogas slurry tank to manufacture foliar fertilizer, and the biogas residues are utilized manufacture solid particle fertilizer.