Extruded granular fertilizers (also known as compacted granular fertilizers) are produced by mechanically compressing powdered fertilizer raw materials into granules. Their key features are as follows:

1. Process Characteristics

• No High-Temperature Drying Required:
  Extrusion granulation is typically performed at room temperature or low heat, making it suitable for heat-sensitive materials (e.g., biofertilizers, organic fertilizers).

• No Chemical Reaction:
  The process involves physical compression, preserving the original chemical properties of the raw materials.

• Flexible Formulation:
  Allows blending of various materials (inorganic fertilizers, organic fertilizers, microbial agents, etc.) for customized production.

2. Product Characteristics

• High Granule Hardness:
  Compacted granules have high density and strong compressive resistance, reducing breakage during transport and storage.

• Slow-Release Potential (Partial):
  If binders or slow-release materials (e.g., humic acid) are added, nutrient release can be prolonged.

• Uniform Appearance:
  Granules are evenly sized (typically 2–5 mm) with a smooth surface, enhancing marketability.

• Low Moisture Content:
  Finished product moisture is usually <5%, minimizing caking.

3. Applicability and Pros & Cons

• Suitable Raw Materials:

  • Organic fertilizers (composted manure, straw, etc.).

  • Inorganic fertilizers (e.g., potassium chloride, ammonium sulfate in powder form).

  • Functional fertilizers (e.g., those containing microbial agents).

• Advantages:

  • Low investment cost and simple production line.

  • Energy-efficient and eco-friendly, with no waste gas or water emissions.

  • Ideal for small-batch, multi-variety production.

• Disadvantages:

  • Slower dissolution rate (requires microbial or moisture breakdown in soil).

  • Poor granule integrity if raw materials lack sufficient fineness.

4. Applications

• Organic Farming: Production of organic-inorganic compound fertilizers and bio-organic fertilizers.

• Cash Crops: Customized formulas (e.g., fertilizers for flowers, fruits, and vegetables).

• Soil Improvement: Granular fertilizers containing soil conditioners (e.g., humic acid, silicon, calcium, magnesium).

Comparison with Other Granulation Methods

Key Considerations

• Raw Material Pretreatment: Must be crushed to 80–100 mesh to prevent mold clogging.

• Mold Selection: Adjust die holes based on desired granule size and shape (cylindrical, flat, etc.).

• Binder Addition: If raw materials lack adhesion (e.g., potash fertilizers), binders like bentonite or starch may be needed.

Extruded granular fertilizers are well-suited for small and medium-sized enterprises aiming for differentiated products, particularly in organic-inorganic blends or functional fertilizer applications.