Types of Anaerobic Composting and Their Pros & Cons of This Eco Friendly Approach

The process of composting organic wastes in the absence of oxygen with the involvement of anaerobic microbes is known as anaerobic composting. There are many types of anaerobic composting. Some of the easy methods that can be followed by gardeners are

1. Bokashi method
2. Trench method 

1. Bokashi method: 

Bokashi is a popular anaerobic composting method. The term Bokashi is a Japanese word that it refers to “fermented organic matter”. Generally, an inoculant is used to follow the bokashi method of composting as it contains the required microbes to ferment the wastes by controlling the bad odours. Using this anaerobic method, you can get the compost in no time (within 40 days). 

Go through the links below to know about other types of composting: 1. Composting and its types 2. Aerobic composting and its types 3. Indoor /bokashi method of composting 4. Vermicomposting 5. Special methods of composting (Indore, Banglore, Coimbatore, NADEP)

Essentials for Bokashi method: 

1. Any container with an airtight lid
2. Bokashi bran
3. Kitchen scraps
4. Filter and tap
5. Soil/Coco peat

Any container with an airtight lid: 

As it is an anaerobic composting this method needs an airtight container of any size (depends on kitchen wastes that a family produce) to ferment the food scraps. It should be made/designed in a way that it should lift the composting material to drain any liquid to the bottom of the container or bin. 

 If you wish to prepare compost in no time, you can either manage to set up a bin like mentioned above or buy a ready-made Bokashi bin online .

Bokashi inoculant: 

When you buy a bokashi compost kit, you will get a packet containing microbial inoculant in the form of powder. This medium is more or less made of brans/mill runs of grains (like rice, wheat), sawdust, dried leaves and is inoculated with anaerobic microbes like yeasts (Saccharomyces spp), lactic acids producing bacteria (Lactobacillus spp), purple non-sulfur bacteria (Rhodopsuedomonas spp). These anaerobic microbes help in the fermentation of kitchen scraps without producing foul odours.

Kitchen scraps: 

All the kitchen scraps like vegetable/fruit leftovers, peels, meat, skin, dairy products can go into the bokashi composting bin. Make sure you cut any wastes into small pieces before introducing them into the bin. The quality of the bokashi tea and compost completely depends on the wastes you put into the bin.

Kitchen scraps should be layered with sprinkling of inoculant powder in between them. Do not open the lid more than once a day (to add kitchen scraps) as it may kill the anaerobic microbes due to their contact with the oxygen. So make sure you close the lid tight.

Filter and Tap:

Due to the fermentation, food materials break down and release some liquids. These liquids are rich in nutrients and need to be separated to prevent the drowning of kitchen wastes. In a ready-made set-up, a filter and a tap are provided to ensure the collection of these liquids. The filter (lifts kitchen waste from the bottom of the bin) takes a role in draining these liquids to the bottom of the compost bin and the tap at this level helps in collecting the liquid from time to time. This liquid is otherwise known as “Bokashi Tea”.

This liquid/liquid fertilizer (as it contains the goodness of nutrients) can be used to fertilize plants after diluting them with water. You can even pour this liquid (without diluting) to clean your drains/pipelines.

Soil/coco peat:

After few days(15 days), kitchen wastes break down and decompose completely by anaerobic fermentation. Now this pickled wastes need to be left for curing. This phase is known as maturation. You can either bury these fermented wastes in your garden for maturation or can be layered with soil or coco peat in a container under shade. After 15 days of maturation, you can either use this compost to fertilize your plants or can be used as a soil amendment. Additional compost can be stored in a cool place that is away from direct sunlight.

You can try the bokashi method of composting by buying an indoor composter (Trustbin). Click the link to know more about the process of composting using an indoor composter.

Advantages: 

• Fastest anaerobic composting process.
• Kitchen scraps get converted into compost in less time.
• does not require turning.
• Does not produce greenhouse gases.

Disadvantages: 

• Applied only in small-scale composting.

2. Trench method of composting:

The trench method is one of the anaerobic composting process (not always. Depending on the trench’s depth) and it is an oldest method of enriching the soil, which has been followed for thousands of years. It is also the easiest way to enrich the soil and a convenient method for those who can’t compost waste in bins (who can’t handle the mess/odours).

Unlike regular composting methods, the trench method can be useful to compost the wastes like meat and dairy products along with the regular kitchen scraps and garden wastes. After few months of decomposing, planting can be done directly above those trenches by which plants acquire required nutrients from the composted materials. Even pet waste can be composted in trench methods. 

Steps to compost in trenches: 

1. Choose a location where you want to grow edible plants in future.

2. Dig a long narrow ditch (trench) about 45-60 cm deep (depending on the amount of waste you compost) in the late fall (before the ground freezes) so that materials will be decomposed by spring.

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3. Add organic wastes (kitchen scraps, garden wastes like dry leaves, grass clippings, soft twigs, meat) about 15-30 cm and cover it with soil.

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4. Now cover these organic wastes with the displaced soil and give a modest press. Mark the area with the date to remember and avoid accidental digging in that area.

5. Cover the enclosed trench with mulches like leaves, straw or shallow-rooted plants/cover crops to avoid weed growth on trenches.

 
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Anaerobic microbes (sometimes aerobic microbes and earthworms take a role if the trenches are shallow) act on composting materials to decompose them. Within 3-4 months (depends on wastes used, microbial count and type of soil) wastes get decomposed and planting can be done above it.

Points to be noted about trench composting: 

• The trench should not be dug until the wastes are completely decomposed.
• Food scraps should not be grown above trenches where pet wastes are composted while ornamental plants can be grown over them.
• Do not add wastes like branches, wood chips, hard twigs as they take a longer period to decompose.
• Make sure your composting material is below 30 cm of the soil cover to prevent the attack of rodents.
• Wastes like meat and dairy products can be avoided if you plan to compost for short periods.

Types of trench composting:

• Dig and drop method: this type of trenching can be done at any and many points in your garden. dig a hole of 30 cm, drop the wastes and cover the holes with at least 4-6 inches of soil. This adds nutrition to your garden.
  
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• Trench between rows: Trenching is done between wide planted rows. So that plants on both rows obtain nutrients from it.
  
  
  

• Side dress method: Dig trenches around plants (a little away from root zone) and deposit daily wastes in them. 
  
  
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• Trench rotation method: Divide your entire garden area into three parts i.e. walking space, growing area and composting area. Rotate these areas every year so that you can trench compost in all three areas and make all the garden area productive. 
  
  
  

Advantages: 

• Increases the populations of earthworms and useful microbes in your garden.
• Increases soil fertility by increasing the organic matter and nutrient content in it.
• No foul odours.
• No threat of rodents or flies
• No turning/watering.
• No digging out
• Planting can be done directly over the trenches.
• Pet waste can be composted
• Wastes like meat, dairy products can be composted.

Disadvantages: 

• Digging is a task
• Takes a longer period for decomposition.

FAQs Related to Anaerobic Composting

1. What is the bokashi method of composting?

Bokashi is a method of composting that was first introduced in Japan. Organic wastes get fermented by anaerobic microbes within 15 days and can be used on plants after leaving it to mature (in pits or with soil/cocopeat) for another 15-20 days. Bokashi powder helps in fermenting the wastes without producing foul odours.

2. Can I put coffee grounds/eggshells in bokashi bin?

Yes. wastes like coffee grounds, eggshells, paper towels, meat, dairy products, can be composted in the bokashi method.

3. Can I place the bokashi bin outside?

Bokashi bin should be maintained indoors. and it should be kept away from direct sunlight. The heat from sun rays kills the anaerobic microbes and result in improper/poor fermentation.

4. How deep should I bury the fermented bokashi compost for maturation?

Dig a hole of 30 - 40 cm (depends on the quantity of waste) deep in your garden and add the fermented waste. Cover it with soil and make sure that the waste is covered with at least 15 - 20 cm of soil. If you do not have a garden/space to bury the fermented waste, you can allow it to mature with the alternate layers of soil/coco peat for the same purpose (maturation).

5. How long does it take for trench composting?

Generally, it takes around 3 months (in humus-rich soil) for the kitchen wastes to decompose. It may take a little long (6 months - 1 year) when you add materials like meat as it takes a longer time for the breakdown. The time for composting also depends on the type of wastes you add and type of soil in which you bury the waste.

6. Is it good to trench compost?

Composting in trenches has many advantages as this method is not associated with problems like turning, rodents attraction, flies, foul odours. In addition to these, you can grow plants directly above the trenches (after few months) without digging out the trenches.

7. Do rats create problem in trench composting?

Yes, as gardens are a good source of food, rats burrow into the soil to stay within proximity to the food. If you trench compost in gardens, rats may get into the trenches and end up eating them all in the meantime. So make sure that your gardens are free of rats by block the rat holes if any. 

8. How can I compost without attracting rats?

If you are composting materials like meats, fish, they produce strong odours that attract rats to the trenches. But if the wastes are buried at least 30 cm deep into the soil, your trenches can escape the threat from rats.

9. Can I compost pet waste in trenches?

Yes, you can compost pet waste in trenches if you do not intend to grow edible plants above it. It is not recommended to grow edible plants above trenches that are composted with pet wastes while ornamentals/flowers can be grown for landscaping.

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