Methods of Composting

Methods of composting:

Compost can be prepared in many ways by using raw materials like farm waste, kitchen waste, town refuse, cow dung, cow urine. All these raw materials undergo aerobic or anaerobic decomposition in certain periods resulting in a finished product that is completely organic and rich in nutrients. Apart from providing nutrients to plants, compost benefits in many other ways.

• Act as a soil amendment.
• Helps retaining moisture.
• Reduces the use of chemical fertilizers and saves those expenses.
• Increases the population of beneficial microbes.
• Decreases the carbon footprint .

Compost is a boon to gardens and farmers as it has all the goodness of organic materials. Based on the combinations and layering of raw materials, compost can be prepared in many ways. Some of the popular methods of composting are 

1. Bangalore method of composting: 

This Bangalore method of composting is developed by scientist Dr. L.N. Acharya in 1939 (at IISC Bangalore) to make use of town residues and night soil. It is an anaerobic method that is conventionally carried out by digging trenches or pits. This method is mainly suitable for scanty rainfall areas.

Pit preparation: 

 Pits/trenches should be dug 1 m deep while length and breadth can be varied according to the land availability and volume of wastes to be composted. 

Filling the pit:

The pit should be filled with alternate layers of organic residues and night soil and could be covered/plastered with a layer of soil/earth to protect the compost from external elements like rain and flies. It is necessary to have sloping walls and sloping bottom to prevent the waterlogging conditions in the pits/trenches

• At first, 15 cm of organic refuse is added at the bottom of the trench/pit.
  
  
• A 5 cm layer of night soil is spread over the refuse layer
  
  
• This alternate layering is carried out until the pit is full. 
  
  
• Now, these layers of wastes/pit are covered with 15 - 20 cm of refuse above the ground level.
  
  
• Now the pit is left undisturbed (without turning) for 3 months. Meanwhile, a reduction in the volume of the wastes takes place.
  
  
• Alternate layers of refuse and night soil are added again on top of reduced the contents.
  
  
• Now the pit/trench is ultimately covered with a layer of soil/earth in a dome shape. This layer prevents unwanted organisms to enter the compost and also helps in moisture losses from the compost.
  
  
• For initial 8 -10 days, aerobic composting takes place while, anaerobic composting takes place at a slower rate thereafter.
  
  
• Compost will be ready in six to eight months. 

Nutrient composition of the Bangalore compost:

• Nitrogen = 1.5%
• Phosphorus = 1%
• Potassium = 1.5%

Advantages: 

• Compost is protected from altering weather conditions.
• Problems such as breeding of flies, moisture loss 
• No need of turning
• Protected from rains

Disadvantages:

• Requires a long time for the stabilization of the materials
• Need more load space.
• Expensive to follow.

2. Indore method of composting:

Indore method of composting was developed by A. Howard and Y.D. Wad (at Institute of Plant Industry, Indore). It is an aerobic composting that is associated with turnings when needed.

Raw materials used for Indore method of composting: 

1. Plant residues (all the weeds, prunings, stalks, stems, fallen leaves, chaff, and fodder leftovers)
2. Animal dung and urine
3. Urine soaked earth/mud
4. Inoculum 
5. Wood ashes
6. water

Each type of plant residue is laid out in layers of about 15 cm until the heap attains a height of 1.5 meters. Now the heap is cut into vertical slices so that each slice contains all types of wastes. These slices (about 20-25 Kgs) of organic wastes are spread in the cattle shed to serve as bedding for a complete night. This bedding along with dung, urine, and urine-soaked mud is collected on the next day. These materials are used in filling the pits of Indore composting. This bedding and collections continues until the organic wastes get over(or until pit gets full).

Location of the Indore composting pit: 

The location of the pit should be close to the cattle shed and water source. If the pit is located in slope areas, rainwater gets collected into the pits so the level of site of the pit should be a little high to prevent the entry of rainwater into the pit. Constructing a temporary shed over the pit is highly recommended to protect the pits from heavy rains.

Measurements of the pit:

Length: 3 - 3.5 m (depends on the quantity of waste)

Breadth: 1.5-2 m

Depth: 1 m

Filling the pits:

• At first, organic materials (dry wastes) that are brought from the cattle sheds are spread at the bottom for 15-20 cm
  
  
• Now a slurry made from 4.5 kgs dung, 3.5 kgs urine-soaked mud, and 4.5 kgs of inoculum from a 15-day old compost pit is added evenly over the dry waste layer.
  
  
• Water is sprinkled to make the materials wet enough (50% moisture should be maintained)
  
  
• In this way, the pit should be filled (within 1 week) until it reaches 1 foot above the ground level.
  
  
• Now the pit should be covered with a thin layer of bedding material with wood ashes and urine-soaked mud. 

Turning: 

Turning of the materials should be done to aerate the pits for proper decomposition of the wastes.

• 1st turning: Between the 10th-15th day after filling the pits
  
  
• 2nd turning: After 15 days of the first turning
  
  
• 3rd turning: After 2 months of the second turning

Nutrient composition:

• Nitrogen:       0.8%
• Phosphorus:  0.3%
• Potassium:    1.5%

Advantages: 

• Requires short period for stabilization of the materials
• Need less land space
• This method is not associated with odour problems
• It is a complete environment friendly process.

Disadvantages: 

• No protective layer
• Requires regular turning to ensure proper aeration in the pits
• Composting pit needs to be at an elevated site, near to cattle shed and water source 
• Need manpower for turning
• Associated with problems like moisture loss and breeding of flies.

3. Coimbatore method of composting:

The Coimbatore method of composting was introduced by Manickam in 1967. Composting occurs mainly in trenches/pits under shade. In the initial stage of composting, anaerobic decomposition takes place and it is followed by aerobic decomposition. 

Raw materials for the Coimbatore method of composting:

1. Farm wastes (weeds, straw, leaves)
2. Vegetable refuse
3. Animal dung
4. water

Size of the pit:

• Length: 3.6 m (according to the volume of the wastes)
• Breadth: 1.8 m
• Depth: around 1 m

Filling the pit: 

• A layer of farm wastes and vegetable refuse is spread at the bottom of the pit up to 15 - 20 cm
  .
• A thin layer of wet cow dung (about 5 cm) is spread over the dry wastes.
  
  
• Water is sprinkled to make sure the materials are well moistened. The pit should have 50-60% moisture to carry out the Coimbatore method of composting.
  
  
• This process of filling is continued until the mass reaches the height of 0.6 m above the ground level.
  
  
• Now the mass is covered with a layer of mud to favor the anaerobic decomposition. 
  
  
• Now the pit is left undisturbed for 1 month. Meanwhile, the mass gets flatten due to the decrease in the volume of the mass (due to decomposition).
  
  
•  Now a turning is given after removing the mud plastering over the heap.
  
  
• Hereafter aerobic decomposition takes place. Within 4 months of time process of composting will be completed and the compost will be ready to use.
  
  
• Meanwhile, water can be sprinkled to maintain the moisture in the pit.

4. NADEP method of composting:

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The NADEP method of composting was introduced by N.D. Pandharipande from Maharashtra. This composting takes place in constructed brick tanks and around 2.5 tons of compost can be prepared in short period (4 months) using this method.

Raw materials:

1. Agriculture waste (Weeds, crop residues, forest litter) - 1350 - 1400 kgs
2. Cattle dung/biogas slurry - 98-100 kgs
3. Fine sieved soil - 1675 kgs
4. Water - 1350 - 1400 ltrs

Size of the tank: 

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• Length: 10 feet
• Breadth: 5 feet
• Height: 3 feet

Tank construction: 

• A rectangular tank using bricks and mud (to seal) should be constructed near to cattle shed or farm. Tanks can be constructed either using mud or cement mortar. 
  
  
• To ensure aeration, 6-inch vents are provided by removing alternate bricks after the height of 1 ft from the bottom of the tank.
  
  
• All four walls of the tank need to be plastered with cow dung slurry before filling it. This helps to facilitate microbial activity from all four sides of the tank.

Filling the tank:

• First layer: 4 - 6 inches of stems and sticks are spread at the bottom to facilitate aeration. It is followed by a 4 - 6 inches layer of agricultural wastes (about 10-100 kg).
  
  
• Second layer: A slurry, that is made using 4 - 5 kgs of cow dung and 100 - 125 liters of water is sprinkled over the dry wastes to facilitate microbial activity.
  
  
• Third layer: 60 kg of sieved dry soil is spread evenly over the second layer for moisture retention. This layer also acts as a buffer during the biodegradation of the materials.
  
  
• The entire tank needs to be filled by the same process within 24 hours (not more than 48 hours) of time. 
  
  
• Now a layer of 3-inch sieved sand should be spread and sealed ultimately with a layer of cow dung and mud plaster.
  
  
• After 15-30 days the volume of the materials gets reduced to 2 feet and is refilled with the layers of the dry wastes, slurry, and sand. 
  
  
• Now the entire mass is covered with a thatched roof to prevent the loss of moisture from the tank.

Now the tank is left undisturbed for 3 months. Meanwhile, water is added for every 1 - 2 weeks to maintain the moisture percentage in the tank. If the tank develops any cracks, those can be filled with the slurry to maintain the quality of the compost.

Advantages: 

• A large quantity of Quality compost can be prepared with minimum human effort.
• Compost can be prepared in less time.
• Decrease the dependence on outside inputs (mineral/chemical fertilizers, soil amendments)

Frequently asked questions:

1. What is the advantage of the Bangalore method over the Indore method of composting?

Bangalore method of composting was developed by: Dr. L.N. Acharya.

Indore method of composting was developed by:  A. Howard and Y.D. Wad.

NADEP method of composting was developed by: N.D. Pandharipande.

Coimbatore method of composting was introduced by: Manickam 

It takes around 6-8 months to decompose the wastes as the anaerobic composting occurs at a slower rate.

The NADEP method of composting was introduced by Gandhian worker Narayan Deorao Pandharipande (also known as Nadepkaka) from Maharashtra. The specialty of the NADEP method is that it can produce large quantities of compost in short periods with minimum human efforts and without any additional expenses.

Garden/farm waste, kitchen waste, cow dung, cow urine, straw, hay, water are some of the basic raw materials that are needed to prepare a compost.

Time taken by the following composting processes are

Bangalore method: 6-8 month

Indore method: 4 months

Coimbatore method: 5 months

NADEP method: almost 4 months

References: 

http://www.fao.org/3/y5104e/y5104e06.htm#TopOfPage