What Is The Best Way To Compost Cardboard?

Have you ever wondered what the best way to add cardboard to your compost bin is? Cardboard is a valuable addition that will prevent your compost from getting too wet, but you need to make sure you are adding it in a suitable way to maximize its usefulness in your compost heap.

Cardboard In Compost

You can add cardboard by tearing it up into shreds before you put it in the compost bin. You may also find it beneficial to add water to the cardboard, as this helps it to break down. Cardboard adds “browns” to your compost heap, increasing the carbon and reducing the risk of the heap getting too soggy.

Should I Add Cardboard To My Compost Bin?

Adding cardboard to your compost bin can be useful. In order to operate efficiently, a compost bin must include a mix of “brown” materials and “green” materials. Brown materials are carbon-rich, while green materials are nitrogen-rich. Too much of one or the other will upset the balance of the compost heap and stop it from operating properly.

There are other forms of browns, including dry leaves, straw, nutshells, eggshells, and any woody material from your garden. Some of these will offer more nutrients and structure to the compost, but cardboard is a good substitute if you don’t have enough of these other things.

What Do I Need To Do To Compost Cardboard?

First, assess the cardboard. You should remove all tape, staples, and non-degradable parts (e.g. foil liners). These won’t break down in your compost heap and could contaminate it, so make sure you get rid of them all.

Once you have done this, shred your cardboard as much as possible. Some cardboard tears easily, while you might need to use a box shredder or another tool to break up other cardboard.

The more you can break the cardboard up before you compost it, the better. This will make it easier to mix into your compost bin and aerate, which will encourage it to break down. The cardboard will add structure to the bin, but in large pieces, it may compact and squash the oxygen out.

shredded cardboard

Oxygen is needed for the decomposition process to happen, so it’s important to pay attention to this. Any big pieces of cardboard can cause problems within the heap.

Furthermore, tearing up the cardboard increases its surface area. This exposes more of it to the microbes that are responsible for breaking down the materials in your compost bin, and speeds up the decomposition process.

When you add the cardboard to the bin, make sure you mix it in thoroughly. You can use a garden fork or a large stick for this. The more you combine it with the other ingredients, the faster it will break down.

Can You Compost Glossy Cardboard?

Many people choose not to compost glossy cardboard because they don’t want the inks entering their compost bin. In the past, these inks might have contained harmful chemicals, which could have spread into the soil, and to any crops that were fertilized with that compost.

Now, however, more effort is made to use non-toxic inks. A lot of inks are vegetable-based and contain fewer toxins. This is not true of absolutely all inks, so a lot of people do still prefer to keep glossy cardboard out of their compost bins, but it is probably safer now than it was in the past.

You can compost glossy cardboard if you choose to. If you feel comfortable with the contents and make an informed decision, there’s no reason not to. The cardboard will break down just like unprinted cardboard, and shouldn’t linger in your compost bin for any longer than plain cardboard.

However, it is worth checking that there is no plastic seal over the cardboard. In some instances, manufacturers add a sheet of thin plastic wrap to protect the cardboard. You may be able to peel this off if it is in place.

One way to test for it is to wet the cardboard. If water will not penetrate it, there is likely some sort of barrier, such as plastic. In such cases, you should try to remove the barrier before composting, or put the card in your general waste bin instead. You don’t want to introduce plastic to your compost bin.

Why Should You Water Cardboard Before Composting It?

You don’t have to water cardboard when you compost it, but it’s often a good idea to do so. This is because cardboard is a very dry material, and water is needed for the compost bin to operate properly.

If you add a lot of dry material to a bin that is already dry, the microbes will likely stop operating, because they won’t have enough water. Watering the compost prevents this from happening and speeds up the microbial processes, resulting in cardboard that breaks down more quickly.

Wet Cardboard

If your compost bin is already pretty wet, it may be best not to water the cardboard when adding it. A bin that is too wet is at risk of turning anaerobic (this means it runs out of oxygen and therefore the “good” microbes die off). When this happens, you will end up with methane-producing bacteria that will smell bad, and the compost heap will turn slimy and unpleasant.

You can use dry cardboard to balance things out if this happens, because it will soak water out of the heap and restore the balance. However, assuming that your compost bin is operating normally and isn’t too damp, adding a lot of dry cardboard isn’t a good idea.

Most people toss the cardboard on the compost heap and then lightly water it to stop it from causing problems. This has the added advantage of preventing the cardboard from blowing away if you have an open compost heap.


You can add cardboard to your compost heap by shredding it as much as possible, tossing it in, stirring it, and adding a bit of water if necessary. This should help the cardboard to break down quickly, providing a good boost of carbon.


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    Author, blogger, podcaster, homesteading and permaculture enthusiast. I have a passion for sharing what I learn and helping others on their journey. If you're looking for me, you'll usually find me in the garden.

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