For good composting to take place, it’s important to maintain a balance of nutrients, air and moisture. Bulking agents are added into the compost to help maintain that balance.

In this blog we’ll see how bulking agents help in the process of composting and the real importance of it.

What are Bulking Agents?

Organic material which is added to compost to improve the physical structure of the compost is known as bulking agent. Bulking agents are usually high in carbon and low in nitrogen, the C-N ratio is between 25:1 to 30:1 and is usually added to improve the physical structure of the compost.

Some common material used for bulking are wood chips, sawdust, straw, and dried leaves but other materials such as shredded paper, cardboard, and corn stalks can also be used.

Importance & Benefits of Using Bulking Agents in Compost

Using bulking agents in composting is important for several reasons:

Improves Aeration

Bullking agents help the compost become more poros leading to proper ventilation which is very important for the microbal activity in the pile.

Improves Compost Structure

Bulking agents are good at enhancing the structure of the compost which creates air pockets in the compost and helps improve drainage of the compost too which leads to proer decomposition of organic material in the pile.

Improves Moisture Absorption

Bulking agents are very moisture absorbant and decrease the chances of pile getting waterlogged which can further lead to slowdown and anaerobic activities in the compost pile.

Balances Carbon Nitrogen Ratio

Because bulking agents are high in carbon content and help in making the C-N ratio of the pile balanced for adding it in the soil.

Adds Nutrient to Compost

Bulking agents adds carbon and nitrogen into compost pile which later help in enhancing nutrient content of the soil.

How to Choose the Right Bulking Agent

There are a few more things that you should consider while selecting the right bulking agent for your compost pile:

  • Carbon-Nitrogen Ratio: The ideal C-N ratio of bulking agents is between 25:1 to 30:1 which means that th bulking agents are high in carbn content as compared to nitrogen.
  • Particle Size: Make sure that the bulking agent contains wood chips and other mateirals which are slightly bigger in size so that they make air pockets in the compost pile and help create good ventilation in the compost.
  • Absorption Capacity: The water absorption capacity of the bulking agent should be high, it should be able to absorb water in the compsot and maintain ideal moisture levels for proper decomposition and prevent bad smell.
  • Availability: It’s not important to be very specific about the bulking agents. Add whatever is easily available in your area and make sure it’s in good condition to work as a bulking agent.

Bulking agents are high in carbon and include materials such as:

  • Dry leaves
  • Straw
  • Hay
  • Sawdust
  • Wood chips
  • Shredded paper
  • Cardboard

Benefits and Drawbacks of Different Bulking Agents

  • Wood chips: Wood chips are highly porous which increases their absorption capacity. The only drawback is the wood might be processed and contain metals whcih slow the process of decompositon.
  • Sawdust: Sawdust is also very porous and rich in carbon but the particle size is very small which can lead to poor ventilation in the pile.
  • Straw: The only benefit of straw is that it is available in abundance almost everywhere and is very cheap. On the other hand the absorption capacity is very low and might contain weed seeds.
  • Dried leaves: Dried Leaves are also available everywhere and are cheaper. But the absorption capacity of the leaves is very low and it can also cause compression in the pile due to small size.

How to Use Bulking Agents in Composting

There are several methods by which are used to incorporate bulking agents into the compost, most common methods are mentioned below:

  1. Mixing: This involves blending of bulking agent into the compost and creating a pile which is a mix of organic matter and bulking agent. In this method, there is a uniform distribution of bulking agent.
  2. Layering: In this method, you create layers of organic matter and bulking agents. While layering, you have to make sure that the layers are equal in size and there is a uniform distribution of bulking agent and organic matter.
  3. Top Dressing: As suggested by the name, in this method you create a layer of bulking agent on the top of the pile. It’s hard to get even distribution of bulking agent everywhere in the compost and it majorly remains above the pile till the time you turn the pile.
  4. Trench Composting: In this method, you dig a hole in the land and put the bulking agent along with organic matter into it. The hole is then covered with soil and then left to decompose.
  5. Composting Toilet: In this method, bulking agent is added into toilet bowl after every use, it is then mixed and composted. This is how bulking agent is used to compost human waste and is mainly used in areas with low access to sanitation system.

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