Chicken manure contains abundant organic matter and high levels of nitrogen (N), phosphorus (P), potassium (K), and trace elements, making it an excellent raw material for organic fertilizer. Dry chicken manure contains up to 50% organic matter, 3.2% nitrogen, 3.1% phosphorus (as P₂O₅), and 2.4% potassium (as K₂O). It is rich in nutrients and contains a large amount of protein, making it one of the best raw materials among animal manures for producing organic fertilizer.
1. Main Technologies for Chicken Manure Composting
Chicken manure composting primarily utilizes biological processes combined with advanced mechanical techniques. The most commonly used method is aerobic fermentation. Aerobic fermentation allows the compost to heat up quickly, reach high temperatures, and have a short maturation cycle. The high temperatures effectively kill insect eggs, pathogenic bacteria, and weed seeds in the manure. Furthermore, with effective mechanical stirring, the drying effect is highly significant.
Currently, the industrial composting processes mainly include windrow composting and trough-type aerobic fermentation.
Trough-Type Aerobic Fermentation: This is currently the most effective method for processing chicken manure and is highly suitable for commercialized and standardized production. It combines biological characteristics with mechanical technology, utilizing natural or inoculated microorganisms to fully mature the chicken manure and convert organic matter into humus, carbon dioxide, and water. This method features a short fermentation time, is easy to scale for factory production, is unaffected by weather or seasons, and causes minimal environmental pollution. Depending on the equipment, fermentation troughs are generally 6 m wide, 1.5 m deep, and 50 to 100 m long, and can be customized based on actual needs.
Windrow Composting: This method involves spreading the materials into rows and stacking them outdoors or under a shed. Each row is typically 4–6 m wide, about 2 m high, and of variable length. Air ducts can be installed beneath the pile, though they are not strictly necessary. Windrow composting allows the materials to be placed closer to farmland without requiring specialized factory buildings, but it involves a longer processing time. If done outdoors, it is highly susceptible to weather and seasonal changes.
To achieve commercialized production and management of chicken manure organic fertilizer, this article focuses on the trough-type aerobic fermentation process. The following data is sourced from a bio-organic fertilizer plant: The fermentation trough is 6 m wide, 1.5 m deep, and 60 m long, with a fermentation temperature of 60℃ and a duration of 20 days. At 60℃, combined with mechanical stirring, the fermentation speed is fast, the process is easy to control, it is unaffected by weather or seasons, and it facilitates large-scale standardized production.
2. Process Conditions for Chicken Manure Composting
2.1 Suitable Fermentation Raw Materials
Organic matter serves as the primary nutrient source for composting microorganisms. The demand for carbon (C) and nitrogen (N) elements by these microorganisms must maintain an appropriate ratio, generally considered to be a carbon-to-nitrogen ratio (C/N) of 20~35:1.
Therefore, based on a typical mixing ratio of chicken manure to auxiliary materials of 3:1, the auxiliary materials should have a C/N ratio between 20:1 and 80:1. Common rural organic wastes such as dry straw, corn stalks, fallen leaves, soybean stems, and peanut stems can all be crushed and used as auxiliary materials.
2.2 Appropriate Moisture Content
The optimal moisture content for microbial fermentation is 50%~60%, with an extreme limit of 60%~65%. Thus, adjusting the moisture content to around 55%~60% is ideal. If moisture exceeds 65%, there is a high risk of the compost failing to ferment (a “dead trough”).
Based on multiple measurements, fresh chicken manure has a moisture content of 80%, auxiliary materials 10%, and inoculated materials 40%. In large-scale production, discharged materials from the trough are generally used as inoculants, accounting for 10% of the total volume (minimum requirement). When fresh chicken manure, auxiliary materials, and inoculants are mixed evenly, the resulting moisture content is approximately 60%. Based on this data, the recommended ratio of chicken manure to auxiliary materials is about 3:1.
2.3 Effective Mechanical Stirring
Chicken manure composting is an aerobic process. Due to the high moisture content (60%~65%) and high viscosity in the trough, aeration is extremely poor, requiring mechanical stirring for auxiliary ventilation.
In actual production, the trough temperature is somewhat affected by seasonal temperatures. In summer, when the workshop temperature exceeds 30℃, the fermentation temperature can reach 60~65℃ or even higher. Stirring once every hour facilitates microbial aerobic fermentation and material drying. In winter, when the workshop temperature drops below 10℃, the fermentation temperature only reaches 45~55℃. Since stirring dissipates heat, stirring once every 4 hours helps maintain high-temperature conditions.
3. Production Technical Management
3.1 Control of Chicken Manure and Auxiliary Materials
Depending on local agricultural conditions, organic materials like straw, corn stalks, and peanut stems can be used as auxiliary materials. Based on moisture requirements, the ratio of chicken manure to auxiliary materials is 3:1. For a trough measuring 50 m long, 6 m wide, and 1.5 m deep, each trough requires 150 tons of chicken manure, 50 tons of auxiliary materials, and 22 tons of inoculated materials. These must be mixed thoroughly inside the trough.
3.2 Inoculant Control
Discharged materials from the trough contain numerous thermophilic microorganisms and can be reused as inoculants to accelerate fermentation. The general inoculation rate is 10% of the total volume, which can be increased to 20% in winter.
3.3 Moisture Evaporation and Stirring
Example Calculation:
When the trough temperature is around 60℃, stirring twice a day reduces total moisture by 2%; at 50℃, stirring twice a day only reduces moisture by 1%.
Assuming a trough receives 150 tons of chicken manure, 50 tons of auxiliary materials, and 22 tons of returned materials daily, with a fermentation temperature of 60℃ and a duration of 20 days, the material balance can be calculated.
After 20 days of fermentation and 40 stirring cycles, the moisture content of the discharged material can be controlled at 40%~45%. After sun-drying or oven-drying, it can be processed into a commercial product requiring a moisture content below 20%. Thus, each trough can produce 103 tons of finished organic fertilizer (at 20% moisture) per batch.
3.4 Composting Maturation Cycle
After mixing chicken manure, auxiliary materials, and inoculants in the trough, the first stirring marks the beginning of the fermentation cycle. It generally takes 3–4 days to heat up (7–10 days in winter) before entering the high-temperature phase. If the trough temperature exceeds 55℃, 15 days are sufficient for complete fermentation; if it remains below 50℃, 30 days are required. Therefore, the summer fermentation cycle is generally 18 days, while the winter cycle is 35 days.
If the temperature has not exceeded 40℃ after 10 days, the trough is deemed “dead” (fermentation failed). At this point, moisture must be tested. If moisture exceeds 60%, more auxiliary materials and inoculants should be added; if moisture is below 60%, consider whether the inoculant volume was insufficient.
4. Conclusion
The trough-type aerobic stirring fermentation process utilizes effective microbial strains to treat chicken manure, fully leveraging both microbial action and mechanical stirring. The high fermentation temperatures effectively eliminate harmful elements such as pathogenic bacteria, viruses, insect eggs, and weed seeds. The short drying time enables factory-scale standardized production, eliminates odors, converts organic pollutants into nutrients easily absorbed by plants, and meets harmless treatment requirements.