Cardboard Journey Into Green

There are times where finding enough “browns” for compost can be a tall order. That is why in this post I discuss the use of cardboard and the cardboard journey into green. Cardboard is an amazing resource from carbon, but it requires a bit of prep and some understanding of how it is produced.

Most people do not realize that the paper used to make cardboard is actually pretty high-quality. The inks that are used are all required to be soy-based inks, and the glue that binds cardboard together is often corn-based. The difficulty with cardboard is the tape and the glues and adhesives that OTHER companies might use.

Tapes! And Why I hate them.

A quick word on tapes. Tape on cardboard is the bane of my existence. It is unusable, period. It will NOT decompose, it will destroy your shredder, and it is toxic in that it’s adhesive is usually made of tolulene which contains heavy metals.

The processing strategy I have outlined below will make removing tape a breeze, as the tape will EASILY separate from the cardboard with ease. There is no good tape – even black Amazon tape which uses a soy-based adhesive has strings in it that will clog your shredder.

White Labels

Shipping labels are another issue. They are paper (usually) but sometimes they are plastic. Almost always they are produced from thermo-responsive paper that uses a compound known to be a hormone disruption factor. The UV radiation probably destroys this compound but I do not have data on that.

A good rule of thumb is do not try to recycle cardboard if you are not willing to deal with and manage tape and white labels. White labels are usually temperature responsive thermal print paper which contain hormone disruptor chemicals. Best to avoid both.

The Tape! Remove it!

There is nothing more annoying than finding tape in your compost. It makes you feel like your compost is substandard and it is annoying to collect it piecemeal. Remove it from the waste stream early.

Not All Cardboard Is Alike

Cardboard is a remarkable, high quality source of paper and carbon. It also comes with some limitations that one must understand. Not all cardboard is alike so here are three classifications I find useful in discussing cardboard.

  • Traditional Plain Cardboard (Amazon, moving, plain brown affairs)
  • Bleached or Dyed Cardboard (ny box that has color – especially white boxes)
  • Wax-Coated Cardboard (This is shiny and covered with a thin sheet of plastic printing or such)

The paper and glues used in most cardboard boxes in use today are all either soy or corn-based adhesives. So they are naturally organic. Here is a quick video on just how cardboard is made from pulp to package.

The issue with cardboard is that it is not always clear if the final glue joint is also a corn-based adhesive. Sometimes it is made from a resin, and you have to be mindful that the end user might also use a strong resin-based adhesive. But the cardboard itself is entirely organic.

The glossy printed boxes pose another problem. While the paper is organic as is the ink, the two degrade at vastly different rates and respond to water and UV radiation differently. To make the glossy paper degrade quicker, recyclers use heat and select chemicals to return the glossy paper to pulp.

Since most gardeners do not have that luxury or equipment, I suggest we stick with brown, unbleached boxes just to be safe. The real issue is cardboard that has been bleached white. I am not certain what process is used, and I just try to find another use for that.

The Minor Inconvenience of Readying Cardboard

Cardboard stock is DESIGNED to be durable. Therefore you cannot just process cardboard and use it. It needs to undergo setting in the sun and rain for a short period of time. Chlorinated water is not sufficient for breaking down the bonds and glues of cardboard. Rain and UV work best.

That means a week or two in the elements. This looks bad, but pays dividends. A fantastic and virtually limitless source of browns at your disposal and delivered to your home. You can’t beat that.


After your broken down boxes (yes, you should break them down to expose as much surface area as possible) have weathered outside it is wise to break them down to pieces that actually fit beneath a lawnmower. The lawnmower is the final step in this process.

Lawnmower Prep

First make sure your lawnmower is at least 3/4 HP and your blades are sharp. If you are not sure, it is best to look at the blade first. If you can, remove the blade, clean it and hand sharpen it yourself, or better yet, buy a blade specifically for this task.

Slow and Steady

When you are ready, stack the cardboard in a pattern. The pattern should have air in it so that that as much edge of the boards are exposed against each other as possible. Then slowly mow over them to shred them.

I suggest using a bag on your mower and a semi solid surface as even though the cardboard is wet and weakened it will fly everywhere. You’ll want to be able to collect that confetti, and your bag will clog quickly. But you will have perfectly small and highly shredded cardboard on demand.

Cardboard in a compost pile or garden bed is ideal because it holds water well and breaks down quickly in acidic soil conditions. But it must be smaller to increase the edges that microorganisms can chomp on and hide between. You’ll find this breaks down quite quickly.

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