How To Shred Cardboard For Compost?

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In Brief: How To Shred Cardboard For Compost

When it is impossible to find dry twigs, leaves, or branches for compost, the next best option is cardboard. It will serve efficiently as a carbon source, even if not a first choice. But knowing how to shred cardboard properly to add to your compost pile is important or it will not break down properly. Here we look at why you should shred the cardboard and how to shred cardboard for your compost heap.

In the absence of carbon sources such as dry leaves, twigs, or barks, compost will not form properly. Getting these materials sometimes could be difficult due to weather conditions.

In such times, cardboard becomes a good option for carbon.

This article looks at how cardboard can be shredded for compost, and we discuss its benefits and some issues that may be associated with it.

Why Shred Cardboard for Compost

Is it really necessary to shred cardboard before using it for compost, or is it just an unnecessary process?

The principle behind Shredding Cardboard for Compost

When creating compost, adequate surface area in which quick decomposition can occur is highly necessary. If materials are large and chunky, the surface area is reduced, decomposition is slowed, and materials get clumped up.

This results in poor aeration of the compost, which is not beneficial.

Conditions that aid shredding of cardboard

When shredding cardboard for compost, it is necessary to take some things into consideration.

First, is there plastic present in the cardboard? If yes, then it must be removed as it does not decompose and would be a nuisance in the compost.

Ensure cardboard is completely flattened to aid easy shredding.

What kind of cardboard is being used? Does it have ink and what kind of ink? If the ink is petroleum-based, it may not be suitable for compost, but if vegetable-based, it poses no problem to the compost.

How To Shred Cardboard For Compost

Time needed: 1 hour.

There are different ways in which cardboard can be shredded for compost, and we will look at each of them here.

  1. Classic Shredding Method

    Once plastic and stables have been removed, the cardboard can be placed on a flat surface at a comfortable working height.

    It can then be cut with the aid of a box cutter or a pair of scissors along the corrugated lines.

    The cardboard can be cut into 8 inch-size pieces and further down to 1 inch with the box cutter or if you want to be faster, feed the 8-inch pieces into a shredder.

    The advantage of the shredder is that you get light and airy pieces which are compost suitable.

  2. Wetting Method

    When cardboard is wet, it is relatively easy to tear, and so wetting is a good idea.

    It can easily be achieved by either leaving the cardboard under heavy rains to get wet all through if you live within a high rainfall region.

    Alternatively, the cardboard can be soaked in a large tub for 2 to 3 weeks, after which it can then be shredded by hand.

    If applying this method, you can allow the cardboard to get wet before removing plastics, as this makes it easier to come off.

  3. Lasagna Method

    This is a borrowed method from the lasagna gardening where cardboard is first laid at the beginning and allowed to compost with the soil and vegetation present.

    This is followed by the addition of nitrogen and carbon-rich substances.

    This same process can be employed when preparing compost by alternating cardboard with layers of other green and brown wastes.

    For quick decomposition, you may also sprinkle water in each layer.

    Soil may also be added to aid microbial action, which will help the decomposition of the cardboard. This method, however, is time-consuming as it takes about 3 to 6 months.

  4. Chipper/Shredder

    This is most likely the easiest and most convenient method.

    Using this method, there is no need for pretreatment, such as cutting into smaller bits or damping to ease tearing. It is an easy and instant process.

    All you need do is remove any plastic tape and then feed directly into the chipper or shredder, and in almost a single blink, you have your cardboard completely shredded.

    Watch this video to see how a shredder shreds cardboard.


Not too many things can go wrong while shredding cardboard for compost. We will look at the few issues that may arise while shredding here.

Chemically Treated Cardboards

The use of chemically treated cardboards is not advisable for compost as it may contaminate the soil and harm the plant.

Therefore, it is of the utmost importance to use clean cardboards for shredding when compost is the aim.

Synthetic Substances

When working with cardboard for compost, it is necessary to remove all synthetic materials as these are not bio-degradable and will be of no benefit in the compost.

Rather, they will hinder the quality of the compost in which they are found.

Time Consuming

When composting with cardboard, it is important to note that decomposition may not be instant.

It could take between 3 to 6 months for complete degradation to occur and for suitable compost to be formed. This can, however, be sped up if the cardboard is cut into tiny pieces.

Benefits Of Shredding Cardboard for Compost

There are some benefits to shredding cardboard for compost, as we will see here.

Easier Breakdown

Shredded cardboard is readily broken down, and this helps the improvement of the compost density as well as the structure. If not shredded, the cardboard pieces may clump together and be of no use to the compost pile.

Reduces foul Odor of Compost

Since cardboard falls into the brown zone or carbon-rich zone, when added to compost, it helps in the reduction of foul odors that may result from excessive nitrogen or green sources.

When shredded, the decomposition is faster and will quickly help to neutralize the odors.

Provides Air Spaces

When cardboard is shredded, it is light, airy, and aids in creating air spaces through which the compost can easily get aerated.

As aeration takes place, oxygen, which is needed for microbial action, is readily supplied to the compost heap.

This video highlights some benefits of shredding cardboard for compost:



Can I shred cardboard that has food stains?

Yes, cardboard with food stains can also be shredded for compost, especially if the grease content is not excessive. This will add some nutrients to the compost.

Does cardboard supply any nutrient to the compost?

Yes, cardboard supplies the carbon content needed for the compost to form and serves as an inlet for oxygen, which promotes bacterial action.

Are all cardboards useful for composting?

All cardboards are useful for compost in the absence of other dry materials. However, care must be taken to ensure synthetic chemicals from colored cardboards do not leach into the compost.

My cardboards are very hard, what can I do?

If you have very hard cardboards, it may be advisable to use the wet method of shredding as this poses less stress to you.

Can I use paper scissors for shredding?

Yes, paper scissors can be used for shredding cardboard in the absence of a shredder and box cutter. It may just be a bit inconvenient and require some patience.


As a carbon source in the absence of materials such as dry leaves, twigs, and barks, carbon is quite useful in compost preparation. But getting the cardboard to a useful state for composting requires shredding.

If shredded properly before added to compost, the cardboard will easily disintegrate in the compost to supply the right amount of carbon needed for the compost.