Pit composting and Windrow composting are two common methods of composting organic waste. Let’s look at them in detail.

Pit Composting:

Pit composting is a small-scale method of composting that involves digging a pit in the ground and adding organic waste materials. The pit is covered with soil and left to decompose over time. The capacity of a pit composting system can vary depending on the size of the pit and the amount of organic waste generated. In India, the CPHEEO guidelines recommend the following minimum and maximum capacity for pit composting facilities:

  • Minimum capacity: 100 kg per day
  • Maximum capacity: 5 tonnes per day

Technical guidelines for pit composting in India:

  • Location: Choose a location that is well-drained, away from water bodies, and at a safe distance from residential areas to prevent odor nuisance.
  • Size of the pit: The size of the pit depends on the quantity of waste generated. For a household, a pit of dimensions 1.5m x 1.5m x 1m is sufficient. For larger quantities of waste, the pit can be scaled up accordingly.
  • Lining the pit: The pit should be lined with a layer of concrete to a thickness of at least 5cm to prevent leachate from seeping into the ground.
  • Preparing the composting material: The composting material should be a mixture of brown and green organic waste, such as dry leaves, grass clippings, kitchen waste, and cow dung. The carbon to nitrogen ratio should be between 25:1 and 30:1.
  • Adding the composting material to the pit: The first layer of the composting material should be about 10cm thick. The subsequent layers should be added as the waste is generated.
  • Moisture management: The composting material should be kept moist but not waterlogged. Sprinkle water on the composting material if it appears dry.
  • Turning the compost: The compost should be turned every 10-15 days to aerate it and ensure that it decomposes evenly.
  • Composting time: The composting process takes between 4-6 months. The compost is ready when it is dark brown, crumbly, and has an earthy smell.
  • Using the compost: The compost can be used as a soil amendment in gardens, agriculture, and horticulture.
  • Maintenance of the pit: The pit should be cleaned after every composting cycle. The concrete lining should be checked for cracks and repaired if necessary.

These guidelines can help in setting up a concrete pit composting system that is efficient, easy to maintain, and environmentally friendly.

Windrow Composting:

Windrow composting is a large-scale method of composting that involves piling organic waste materials in long rows, or windrows, and turning them periodically to aerate the compost. The capacity of a windrow composting system can vary depending on the size of the operation and the amount of organic waste generated. In India, the Central Public Health and Environmental Engineering Organisation (CPHEEO) guidelines recommend the following minimum and maximum capacity for windrow composting facilities:

  • Minimum capacity: 5 tonnes per day
  • Maximum capacity: 200 tonnes per day

Technical guidelines for windrow composting in India:

  • Site selection: Choose a site that is well-drained, level, and away from water sources to prevent contamination. The site should also be easily accessible for the transport of organic waste and finished compost.
  • Size of windrow: The size of the windrow will depend on the amount of organic waste generated and the available space. Windrows should be between 1.5 to 2 meters wide and up to 2 meters high. The length of the windrow can vary depending on the amount of organic waste available.
  • Composting materials: The organic waste used in windrow composting should be a mixture of carbon-rich (e.g. dry leaves, straw) and nitrogen-rich (e.g. food waste, green leaves) materials. The ideal carbon-to-nitrogen (C:N) ratio is between 25:1 and 30:1.
  • Windrow construction: Begin by creating a base layer of coarse materials such as twigs or branches to promote air circulation. Then, alternate layers of carbon-rich and nitrogen-rich materials, watering each layer lightly to achieve a moisture content of around 50%.
  • Turning the windrow: The windrow should be turned every 7-10 days to promote aeration and decomposition. Turning can be done using a front-end loader or manually using a pitchfork.
  • Composting time: The composting process can take between 2-6 months, depending on the size of the windrow, moisture content, and temperature.
  • Monitoring: Regular monitoring is essential to ensure that the windrow is decomposing properly. The temperature should be checked using a thermometer, and the moisture content should be monitored using a moisture meter. Adjustments can be made to the windrow, such as adding water or adjusting the C:N ratio, as needed.

Windrow composting is a low-cost and effective way to manage organic waste in India. By following these technical guidelines, you can produce high-quality compost for your garden or farm while reducing waste and promoting sustainability.

Further reading resources: Composting for improved at-source wet waste management >