In an organic fertilizer production line, composting is a core step in achieving both harmlessness and resource utilization of organic waste. Through microbial decomposition, raw materials like livestock manure and straw are transformed into nutrient-rich, mature materials, laying the foundation for subsequent processing.
The first step in composting is raw material preparation, requiring precise control of the key indicator, the carbon-to-nitrogen ratio. Among commonly used raw materials, straw and mushroom residue are high-carbon, while livestock manure is high-nitrogen. These materials should be mixed in a ratio of 25:1-30:1. For example, a mixture of 60% cow manure and 40% pulverized straw can meet microbial activity while minimizing nitrogen loss. Furthermore, the moisture content of the raw materials should be adjusted to 50%-60%. The material should be held firmly in the hand, with water between the fingers but not dripping. If it is too dry, water should be applied; if it is too wet, add dry straw or sawdust.
The composting process requires scientifically controlled environmental conditions. Windrow and trough composting are two common methods used in production lines. Windrow composting involves piling raw materials into long windrows 2-3 meters wide and 1.2-1.5 meters high. Windrow compost is turned every 2-3 days by a windrow compost turning machine to ensure adequate oxygenation within the windrow. Trough composting, on the other hand, takes place in sealed fermentation tanks, equipped with automated turning equipment to precisely control temperature and oxygen levels, making it suitable for large-scale production. During composting, the temperature must be maintained at 55-65°C, which kills insect eggs and pathogens and facilitates microbial decomposition of organic matter. If the temperature is too low, high-nitrogen raw materials should be added; if it is too high, turning should be used to reduce the temperature.
Determining the maturity of compost is crucial to ensuring the quality of subsequent products. Generally, after 20-30 days, the compost is mature when its color turns dark brown, it no longer has a manure odor but instead has a light earthy smell, and it is loose and free of noticeable lumps. At this time, the organic matter content of the composted material is greatly increased, and it is rich in nutrients such as amino acids and humic acid. It can not only provide nutrients for crops, but also improve soil structure. It is an indispensable “nutrient conversion station” in the organic fertilizer production line.