How is organic fertilizer produced from crop straw?

Converting crop straw into organic fertilizer not only addresses the pollution caused by straw burning but also improves soil structure and fertility; it is a common raw material strategy for organic fertilizer plants. Materials such as corn, wheat, or rice straw can be used. The production process consists of three main stages: pre-treatment, aerobic fermentation, and post-treatment. Huaqiang Heavy Industry offers a complete range of equipment for these processes.

The first step is raw material pre-treatment. Because straw has coarse fibers and a high carbon content, it cannot be composted directly. It must first be shredded into 5–10 mm pieces using a straw crusher to increase the surface area, facilitating decomposition by microorganisms. Since straw has a high carbon-to-nitrogen (C:N) ratio, it should be mixed with livestock or poultry manure (such as chicken or cow manure) to adjust the overall C:N ratio to between 25:1 and 30:1. The moisture content of the mixture should be maintained at 55%–65%. Specialized microbial inoculants are added, and the mixture is thoroughly blended using a mixer. If the proportion of straw is too high, a small amount of urea can be added to supplement the nitrogen source and ensure the fermentation process begins effectively.
The second step is high-temperature aerobic fermentation, which is the core stage of straw-based organic fertilizer production. The material is placed into fermentation tanks or designated composting areas, where a trough-type compost turner is used to continuously turn the material and supply oxygen. The temperature of the compost pile must reach above 55°C and be maintained for at least 7 days; this process eliminates insect eggs, pathogens, and weed seeds, ensuring the product meets safety standards. If the temperature exceeds 65°C, the material should be turned to lower the temperature and prevent beneficial bacteria from being killed by excessive heat. In large-scale production, the primary fermentation typically takes 10–15 days, followed by a secondary maturation phase. During this time, the organic matter decomposes fully; the material turns dark brown and loses any pungent odor, signaling that the composting process is complete.
Once fermented and matured, the material moves to the post-treatment stage. A rotary screen (trommel screen) is used to remove any large, undecomposed pieces of straw and other impurities. For the production of powdered organic fertilizer, the material can be packaged directly after screening. If granular organic fertilizer is desired, the material is fed into granulation equipment—such as a disc granulator or a new type organic fertilizer granulator—to form granules. The finished granules are then dried and cooled as needed, followed by automated packaging and storage.
Many small-scale processing plants often encounter common pitfalls: incomplete shredding of straw, an imbalanced carbon-to-nitrogen ratio, or insufficient oxygen within the compost pile—all of which lead to slow fermentation and foul odors. It is strictly prohibited to apply uncomposted straw-based fertilizer directly to the soil, as it may undergo secondary fermentation, causing "root burn" to crops. Based on the specific characteristics of straw as a raw material, Huaqiang Heavy Industry offers customized straw-based organic fertilizer production lines tailored to various capacity requirements. These solutions enable enterprises to achieve the circular utilization of straw resources, reduce raw material procurement costs, and establish a comprehensive organic fertilizer production system.