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Can You Compost Mulch? The Things You Should Know First

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Mulch keeps the ground moist and cool, reduces weeds, and provides plants with nutrients. Mulching has many benefits, but what about when it becomes too aged or rotted? 

Mulch can be composted. Organic mulch, such as wood chips, can be composted by mixing the mulch directly into the compost pile or bin. Breaking the mulch into small pieces and soaking it with water before composting will help with a faster decomposition. Artificial mulch should not be composted.

The nutrients derived from composted mulch can benefit plants by supplying them with organic nutrients.

This article explains the benefits of composting mulch, the type of mulch to compost, and how to make it break down faster without compromising your compost bin or pile.

Can Mulch be composted?

Can You Compost Mulch

Mulch can be composted when mixed into a compost pile or compost bin. Smaller-sized chips will tend to break down faster than larger-size chips.

The more organic the mulch, the easier it will be to break down by the bacteria and microorganisms within a compost bin or pile.

The nutrients gained from composted mulch can be used to feed plants when mixed into the soil as an amendment.

The compost can also be spread on top of the soil around the root system and will then trickle its way into the soil when the plant is watered or when it rains.

Artificial mulch, like rubber mulch, should not be composted.

How Long does Mulch take to compost?

Mulch lasts anywhere from 4-7 years when laid on the ground, but when placed into the compost, it can break down within 4 to 6 months. 

The moisture and the bacterial activity within a compost pile or bin aid in the speedy disintegration of mulch chips.

The composting time is significantly reduced if the mulch is broken down into smaller chips. This increases its surface area and allows more bacteria to act in its breakdown into compost.

It’s like reaction rates in chemistry: A larger surface area will allow for more activity.

Placing mulch into a more established compost pile or bin will also speed up the decomposition of the mulch because there will already be an established colony of bacteria and microorganisms ready and waiting.

Additionally, when placing mulch into compost, you should mix the mulch into the compost rather than just layering it on top. This helps for faster decomposition and prevents compaction and oxygen restriction for the microorganisms.

Can Non-Organic Mulch Be Composted

Artificial mulch cannot and should not be composted because it may never break down depending on what artificial material they were made of.

Mulch made of plastic or other synthetic materials cannot be composted.

These mulches should be disposed of properly because they could leach chemicals into the ground which can get into the waterways. This can lead to big health problems in the long run.

How to prepare Mulch to be composted

Although mulch can be scooped up and just placed into a composting pile or bin, there are some preps you can do to help give an extra boost or even reduce the time it takes to be broken down.

Break up into smaller pieces

The mulch should be broken into smaller pieces so that it has a greater surface area.

If you have any kind of wood mulch, cut it into small pieces by using a wood chipper.

If you don’t have any type of fancy machinery, I found that works well by placing the mulch on the driveway and driving the car over it a couple of times.

This softens the mulch and makes it easier to soak in water before placing it into compost.

Soak the Mulch 

Adding water to the mulch before placing it into your compost pile or bin helps with decomposition.

The water soaks into the pieces of mulch and makes it easier for microorganisms within the compost pile to break down into beneficial nutrients.

The mulch can be soaked with a garden hose when watering the plants and allowed to sit for an hour or two, after which it can be removed and placed into the compost.

Best Type of mulch to Compost

Organic mulch is the best type of mulch that can be composted. This type of mulch is usually wood chips that are not heavily treated with chemical additives.

Many different kinds of mulch are considered “compostable” or “biodegradable”. Some examples include straw, hay, leaves, grass clippings, pine needles, paper products, cardboard, and shredded newspaper.

These mulches can be added directly to your compost pile or bin without any preparation.

Types of Organic Mulches

  • Wood Chips, Nuggets, or Bark
  • Straw
  • Newspaper or Cardboard
  • Grass Clippings
  • Cocoa Chips
  • Coffee Grounds

Types of Inorganic Mulches

Can I put mulch in the bottom of my compost bin?

 Old mulch is perfect for lining the bottom of a compost bin because of its rigidity, it can take the weight of the materials above it.

Additionally, mulch chips can take some time to be broken down, so during this time, they can also act as a support material for other lighter compost materials.

If the lighter material was to be placed first into the compost the weight of the mulch will compress the lighter material cutting off air circulation cause anaerobic breakdown, which can lead to a very foul-smelling compost.

Compost Mulch Vs. Mixing it Into the Soil

When Mulch is mixed directly into the soil, microorganisms, and bacteria begin to break down the wood chip there would be an initial deficiency of nitrogen in the soil as the microorganisms use it to decompose the wood chips.

This would temporarily rob the plants that are currently in the soil of nitrogen.

They will start showing signs of nitrogen deficiencies which will include yellowing of leaves because they are unable to make sufficient chlorophyll.

The decomposers consume the organic matter, and the nitrogen contained in the dead organism is converted to ammonium ions. The ammonium is then converted to nitrates by the nitrifying bacteria.

 Composting mulch eliminates the risk of creating a nitrogen deficiency within the soil which can cause the above-mentioned nutrient deficiencies.

Is Old Mulch Bad for Plants?

One of the most common misconceptions about mulch is that it’s bad for plants. Actually, mulch can be great for plants as long as you’re using the right kind and applying it correctly.

Old mulch can be mixed in with the soil, which would then be broken down into nutrients for the plants. It can also be left alone while new mulch is added on top of it. Eventually, the old mulch will turn into soil as time passes.

The aerobic decomposition of the mulch by the bacteria and microorganisms will add beneficial nutrients to the soil for the plants while building a healthy soil structure and increasing drainage and aeration for the plant’s roots.

How to dispose of old Mulch

Composting isn’t an option if you have limited space or dyed mulch. You’ll need to bag up the old mulch and take it to your waste management facility.

Never burn old inorganic mulch because it can release toxic gaseous chemicals. However, organic mulch can be burnt because it’s like burning a piece of wood without chemical additives.

You can also call a professional landscaping company to dispose of your old mulch. Although it may be at a small cost, it will benefit you and the environment.

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