Mechanized Rice Straw Composting

Mechanization Process

The mechanization of organic fertilizer production combines physical and biochemical effects to optimize the efficient composting process and the quality of organic manure. This technology has been verified in Vietnam with the following characteristics:

• Productivity: 30 – 50 tons/hour for each batch, depending on the capacity of the machine.
• Composting time: Approximately 45 days for the manure to reach market quality.

Composting process

Step 1: Building composting windrow

Depending on practical conditions, the materials used for compost windrow can include:

• Straw and animal manure, or
• Straw, soil and N supplements (such as Urea).

Prepare a compost windrow in layers (20 cm) alternating between straw and cow manure (or soil) with a width of 1.2 m; height of 0.7 m.

Make sure the mixing component has a C/N ratio of 25 – 30 for optimal decomposition.

Step 2: First turning of the windrow by a compost windrow turner

In the process of using compost windrow turner, microorganisms or enzymes are mixed with water and sprayed into the windrow during turning. Key points to note while doing this process include:

• Speed of the machine: 1.5 m/min, (1.2 – 1.8 m/min, depending on the size of compost window)
• Ensure the moisture content of materials in the window is 50-60% MC.

Step 3: Incubation stage creates a decomposition environment (heat, moisture and pH)

After the first turning, use nylon canvas to cover the compost.

• Temperature: 50-70°C. The windrow is covered with canvas when the temperature is low; Open the canvas and use the mixer when the temperature is > 70°C.
• Humidity: 50-60% MC. This parameter is kept at the specified level by adding water.
• pH: 6.5-7

Step 4: Stage for ventilation and cooling

After the heating stage, when the temperature is too high, and usually after 10-15 days, use the mixer to mix it up to increase ventilation, oxygen and uniform quality. Parameters to be controlled:

• Temperature: 30 – 50°C. Use nylon canvas to cover the windrow when the windrow temperature is low or when it rains; Open the canvas when turning or when the temperature is > 50°C.
• Moisture: 40-50% MC.

In order to reduce costs and increase quality, it is possible to mix organic ingredients in the windrow with the ratio of 40% straw manure: 40% coir: 40% rice husk ash (at the same moisture content).

Step 5: Finishing stage: organic fertilizer

Depending on the type of input materials, about 30 – 45 days after the first turning, the finished product is ready-to-use organic fertilizer. Products with 30 – 40% moisture content, can be screened to remove large impurities.