In the composting of organic fertilizer production line, ventilation has the functions of oxygen supply, heat dissipation and water removal. Ventilation control depends on the air supply mode to a large extent.
① Tipping (natural ventilation)
② Forced ventilation includes positive pressure blast, negative pressure ventilation and mixed ventilation composed of positive pressure blast and negative pressure ventilation;
③ The combination mode of dump and forced ventilation;
④ Passive ventilation. The "chimney effect" caused by the rise of hot gas causes air to pass through the stack, which is called passive ventilation. The composting system applying this ventilation method is called passive ventilation stacking system. As shown in Figure 1, with the hole of perforated pipe facing upward, it does not need to turn over and forced ventilation. Compared with the stack system and the static stack system with forced ventilation, it greatly reduces the investment and operating costs. Natural ventilation and passive ventilation are often used in strip stack system, while forced ventilation is used in static stack system and reactor system. In different composting stages, the turning frequency of the stacking system is different, which should be determined according to the specific situation. The temperature is usually used as the mark of whether to turn the pile (the center temperature of the pile is 55 or 60 ℃). For example, rice straw, rice husk, hay, dry leaves, wood chips or sawdust are used as adjusting agents, and the moisture content of the mixture formed with sludge is about 60%. After the pile is built, it is turned over 3 days after the pile is built, and then every other time Turn the pile once until the fourth time, and turn the pile every 4 or 5 days after the fourth time. If waste paper is used as conditioner, as long as the moisture content of sludge mixture does not exceed 50%, it can be turned over at the following frequency.

Different ventilation methods have different effects on the composting process of organic fertilizer production line. Natural ventilation, passive ventilation and forced ventilation were used to compost pig manure (moisture content as high as 76%). The results showed that under passive ventilation and forced ventilation, the composting temperature decreased faster, but they could supply oxygen to the compost more effectively. Compared with other ventilation methods, forced ventilation is easy to operate and control, and is the most effective way to provide oxygen for the biodegradation of stack. However, it has obvious cooling effect on the stack near the vent pipe.