Granular organic fertilizer is widely used in agriculture due to its balanced nutrients, ease of application, and long-lasting effects. Standardized factory production enables effective control over fertilizer quality. The organic fertilizer manufacturing process is rigorous and systematic, comprising six main stages—raw material pretreatment, fermentation and maturation, crushing and mixing, granulation, drying and cooling, and screening and packaging—with strict operational requirements for each step.
Raw material pretreatment forms the production foundation. Factories typically utilize organic waste such as livestock manure, crop straw, oilseed cakes, and spent mushroom substrate. Impurities like stones and plastics are removed, and equipment is used to adjust the moisture content to approximately 55%. Biological inoculants are added to ensure optimal conditions for subsequent fermentation. During this stage, it is crucial to balance the raw material mix to prevent nutrient deficiencies caused by relying on a single source and to strictly exclude moldy or contaminated materials.
High-temperature fermentation and decomposition constitute the core stage. The pre-treated raw materials are transferred to the fermentation workshop, where windrow or in-vessel (trench-style) fermentation processes are employed, involving regular turning and aeration using a compost turning machine. A 15–20 day high-temperature fermentation period thoroughly eliminates insect eggs, pathogens, and weed seeds while fully decomposing the organic matter. Operations require strict temperature control—maintaining 55–65°C for sterilization; excessive heat causes nutrient loss, while insufficient heat fails to achieve harmlessness. Adequate oxygen supply must also be ensured to prevent anaerobic fermentation, which causes unpleasant odors and incomplete decomposition.
The decomposed material is finely crushed and screened to produce a uniform powder. Nitrogen, phosphorus, potassium, and other macro- and micro-nutrients are added as needed, followed by thorough mixing to ensure nutrient uniformity. The mixture then enters the granulation stage, where a disc granulator forms the powder into granules with diameters of 2–4 mm. Consistent feeding rates and moisture regulation are essential to maximize the granule formation rate and minimize the production of fines (broken granules).
The formed granules undergo rotary drying and air cooling to reduce moisture content to below 20%, preventing mold and clumping. Finally, screening equipment separates the qualified granules; fines are recycled for reprocessing, while the finished product is sealed, packaged, and placed in storage. Throughout the organic fertilizer production process, attention must be paid to workshop ventilation and dust control to prevent dust pollution. Finished products require storage in a dry, light-protected environment; furthermore, production standards must be strictly adhered to—preventing the release of incompletely decomposed fertilizer—to avoid root burn and the proliferation of diseases.
