How To Shred Cardboard for Compost? (3 Easy Ways)

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When you are creating your compost bin using any waste that you may have lying around you need to be careful what you throw in. Many times, you may be surprised to find that people are not always aware of how things need to be thrown away. Almost every piece of composting material needs to be prepared in some odd way, with cardboard easily requiring the most work to be properly added to your compost bin. 

You should be cutting the cardboard into little pieces before mixing them in with other waste material that you are planning on adding to your compost bin. If you want to create a separation layer with the cardboard you still need to shred them by hand, with scissors, or with a shredder. Shredding the cardboard too small is not an issue, however, they should never be any larger than half an inch square. 

You need to understand why we shred cardboard before adding it to compost heaps, how this affects the compost and the changes that it makes to the process. Many think the cardboard will not affect only to later learn that it greatly affects the entire system of the compost. Understanding how everything is changed, how to do it properly, and what differences can be made is a vital part of understanding how your compost bin will work properly. 

Why do you need to shred cardboard?

Cardboard is not nearly as heavily processed as bleaches white papers are, cardboard is just a lot thicker and stronger without being much cleaner. This is why you can see a cardboard box dissolve in the rain while a piece of paper may only become oddly textured. However, it does mean that you need to take some precautions when adding cardboard to a compost bin. 

Once you have shredded your cardboard though it will have one quite easy effect on the compost bin when you add them, the cardboard will dissolve. This is because the worms, moisture, and bacteria can easily break down smaller pieces of cardboard. Not only does it create smaller pieces that are easier to digest, but shredded cardboard has more surface area than a solid piece.

This increased surface area means that the cardboard is being attacked from all sides to be broken down into smaller and smaller pieces. Making them completely disappear as the composting takes place, with many people surprised to learn that if done properly you will not see the cardboard at all after a few weeks. It should be noted that like all other paper types it is best to mix in the cardboard with other organic materials that need to be composted. 

What happens when you don’t shred the cardboard?

This is the biggest question that first-time composter haves when they realize how much work needs to go into keeping a compost bin. If you do not shred the cardboard it will create a layered barrier within your bin, with the worms unable to easily access new things above the cardboard. Cardboard may not be perfectly waterproof, but it can offer some resistance to moisture that makes it damaging to your compost bin. 

You will need to ensure that the compost bin is ready to take the cardboard you want to add to it, as the cardboard, even when shredded, soaks up a lot of water from the soil around it. If you are adding an entire flat sheet of cardboard you should be aware that you will be building a new ecosystem above the sheet. Many times, you may want to do this if you have something tougher to be composted on a lower level. Allowing the worms to focus on that before moving on to other materials that you are adding into the compost.

If you have a lot of cardboard that needs to be added to compost bins, either inside or outside, it is best to have the cardboard shredded as fine as possible. Making a sort of mulch from the cardboard instead of just the smaller shredded pieces. This allows the cardboard to be stored and to be mixed in with other materials that will easily make your worms ecstatic when eating the new foods you are giving them. 

How do the worms handle the shredded cardboard?

The worms will not immediately start eating the cardboard you are adding to your compost bin, even if you are adding it in mulch form. Cardboard and other papers need to soak for a few days or weeks to become extremely soft before the worms will start munching on them. However, they will eventually start eating them just as they will everything else. 

Some compost bin owners let the mulch mix in with some wetter foods to induce extra fast composting of this tough material. If you would like the worms to work a bit faster creating an environment where they can easily and comfortably eat through the cardboard will be the best. Many times, the cardboard will be eaten with the things that surround them, which is why you will find that cardboard that is goo does not last long. 

However, it should be noted that some treated cardboards, even with wax treatments, will not dissolve so easily and can take several months to be composted. For this reason, we recommend sticking to outdoor bins that are larger and can be left for much longer times without having to worry. Cardboard will as all other things eventually become nothing but more compost you can use to keep your garden nice and healthy. 

What can you use to shred cardboard?

The best thing that we can find to shred cardboard is a woodchipper, as it easily gets rid of all possible large parts of the cardboard. Though we do realize that not only are woodchippers rare, but they are also rather extreme to get just for cardboard. Apart from the easy-to-use industrial machine, I’d recommend a common office shredder. Just make sure that yours can handle cardboard or you’ll burn it up.

To avoid overwhelming the shredder you can chop the cardboard up into strips or smaller pieces first. This will get you the best and most consistent result for your cardboard shredding. Many times, people are not always aware of the work involved with shredding cardboard believe that they do not need to get something special.

If you have neither a chipper nor a shredder we recommend getting a few good scissors that you are sure can cut through almost anything. This will take you quite a while to do but you can easily cut each piece of cardboard into something much smaller and more manageable than what they were before. When all else fails you can tear through the cardboard, this may be inaccurate, but it can be an oddly soothing experience when getting rid of all your daily frustrations. 

What types of cardboard can be composted?

This is where a lot of people can become confused, but you should be able to compost most cardboard as they will not be mixed in with other substances. However, you will need to make sure that the cardboard has been processed properly. Cardboard boxes will have plastic on them, from stickers, tape, and almost everything else they get into contact with. 

You will need to ensure that whatever type of cardboard you are using has been cleaned and shredded properly. Most of the time cardboard will only receive a covering of wax if they need to be waterproof. This is a natural wax that your worms will be able to easily digest and compost, which makes all types of cardboard perfect for your compost bin. 

You should remember that almost all types of cardboard have some part of recycled material in it and you can see that some types of cardboard have more recycled material in them than others. These would be the cardboards that have a greyish color to them, sometimes with little spots in them as well. The most common place you can find this cardboard is with cereal boxes. 


Cardboard boxes are a readily available source of fiber for your compost bin and will help it retain more shape when it is needed. This is why you will see that composters will usually happily take waste cardboard to add to their bins, as it means they have one less stress to think about. With only a few other paper-like materials being entirely safe to use for your bin. 

Just always be sure that the compost bin has enough moisture to handle the sudden dryness that the cardboard will add!

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