How To Compost Cardboard: The Best Composting Tips

When it comes to composting, many people think of kitchen scraps and yard waste as the primary materials to toss into their compost pile or bin. While these organic materials are indeed essential for a successful composting process, there’s another often-overlooked component that can significantly contribute to your compost’s richness: cardboard. In this comprehensive guide, we’ll delve into the world of composting cardboard, exploring why it’s a great addition to your compost heap, how to do it properly, and the various types of cardboard you can use. By the end of this article, you’ll have a clear understanding of how to turn cardboard waste into “black gold.”

Closeup photo of cardboard scraps which you can compost

Why Compost Cardboard?

Composting cardboard may seem unconventional, but it offers several benefits to both your compost pile and the environment. Here are some compelling reasons why you should consider incorporating cardboard into your composting process:

1. Organic Material Richness

Cardboard, in its various forms, is considered an organic material. It’s made from wood fibers, making it an ideal carbon-rich component for your compost pile. Carbon-rich materials, often referred to as “brown materials,” balance the nitrogen-rich “green materials” like kitchen scraps and grass clippings. Achieving the right carbon-to-nitrogen ratio is crucial for a healthy compost mix, and cardboard can help maintain this balance.

2. Waste Reduction

Cardboard waste, including cardboard packaging, cereal boxes, and shoe boxes, is a common household item that often ends up in landfills. By composting cardboard, you can reduce the amount of waste sent to landfills and contribute to a more sustainable environment. Recycling cardboard is beneficial, but composting takes it a step further by transforming it into nutrient-rich soil.

3. Air and Moisture Regulation

Cardboard is excellent at regulating air and moisture levels within your compost pile. It creates air pockets and helps prevent compaction, ensuring that oxygen can reach the microorganisms responsible for breaking down the organic matter. Additionally, cardboard can absorb excess moisture, preventing your compost pile from becoming too soggy, which can impede the decomposition process.

4. Diverse Cardboard Sources

Cardboard comes in various forms, such as corrugated cardboard, flat cardboard, egg cartons, and more. This diversity allows you to experiment with different types of cardboard to find what works best for your composting needs. However, it’s essential to know which types are suitable and which may contain harmful chemicals or coatings.

Types of Cardboard Suitable for Composting

Not all cardboard is created equal, and not every type is suitable for composting. Here’s a breakdown of cardboard materials you can safely include in your compost pile and those you should avoid:

Acceptable Cardboard Materials:

  1. Cardboard Boxes: This includes cereal boxes, shoe boxes, and pet food bags. Be sure to remove any plastic tape or stickers before composting.
  2. Paper Products: Items like paper towel rolls, toilet paper rolls, and egg cartons can all be composted.
  3. Shredded Cardboard: Using a paper shredder or simply tearing cardboard into smaller pieces can speed up the decomposition process.
  4. Pizza Boxes: While many people assume pizza boxes are off-limits due to grease, as long as the grease is minimal, you can compost them.
  5. Clean Cardboard: Cardboard that hasn’t been contaminated with harmful chemicals, heavy dyes, or excessive inks is safe to compost.

Avoid These Cardboard Materials:

  1. Wax-Coated Cardboard: Cardboard coated in wax or other non-organic materials should not be composted as it can introduce harmful chemicals into your compost.
  2. Shiny or Glossy Cardboard: These types of cardboard often contain modern inks and coatings that may not be suitable for composting.
  3. Heavy Metals: Some cardboard may have heavy metals in their printing inks, which can harm your compost and pose environmental risks.

To ensure that the cardboard you’re composting is safe and suitable, always check for any coatings, inks, or dyes that may be harmful. Remember that removing any non-organic elements like plastic tape and stickers is crucial before adding cardboard to your compost pile.

How to Compost Cardboard

Composting cardboard is a straightforward process, but it does require some attention to detail to ensure you do it effectively. Here’s a step-by-step guide on how to compost cardboard properly:

1. Prepare Your Cardboard

Start by collecting cardboard materials that are safe for composting. These could include cardboard boxes, paper products, and shredded cardboard. Make sure they are clean and free of contaminants like plastic tape, stickers, or heavy dyes.

2. Shred or Tear Into Smaller Pieces

To expedite the decomposition process, it’s a good idea to shred or tear the cardboard into smaller pieces. Smaller pieces have more surface area, allowing for faster breakdown by microorganisms.

3. Layer with Green Materials

In your compost pile or bin, create alternating layers of cardboard and green materials (such as kitchen scraps and grass clippings). The green materials provide nitrogen, while the cardboard offers carbon. This balance is crucial for successful composting.

4. Maintain Proper Moisture Levels

Ensure that your compost pile has the right moisture content. Cardboard can absorb excess moisture, so if your compost pile is too wet, adding shredded cardboard can help regulate moisture levels. Conversely, if it’s too dry, make sure to water it adequately.

5. Turn and Aerate

Regularly turn your compost pile to introduce oxygen and promote even decomposition. Cardboard’s ability to create air pockets will aid in this process.

6. Monitor Your Compost

Keep an eye on your compost pile’s temperature, as it should heat up during the decomposition process. This indicates that the microorganisms are active and breaking down the organic matter. If your compost pile doesn’t heat up, you may need to adjust the carbon-to-nitrogen ratio by adding more green materials or smaller pieces of cardboard.

7. Be Patient

Composting cardboard may take a bit longer than composting some other materials, but it’s well worth the wait. Eventually, the cardboard will break down, and you’ll be left with rich, nutrient-dense compost.

How to Compost Cardboard using the Lasagna Method

The lasagna method, also known as sheet composting, is a fantastic technique for composting cardboard. It involves layering different materials, including cardboard, to create a nutrient-rich compost pile. Here’s how you can use this method effectively:

1. Choose Your Location

Select a suitable location for your compost pile or bin. Ensure it has good drainage and is easily accessible for turning and maintenance.

2. Start with Cardboard

Begin by laying down a layer of shredded cardboard as your base. This will create a carbon-rich foundation for your compost.

3. Add Green Materials

On top of the cardboard, add a layer of green materials like kitchen scraps, grass clippings, and fruit peels. This provides the necessary nitrogen to balance the carbon from the cardboard.

4. Continue Layering

Repeat the process by alternating layers of cardboard and green materials until your compost pile reaches the desired height. Make sure to finish with a layer of green materials on top.

5. Let It Decompose

Allow the compost pile to decompose naturally. Over time, the layers will break down, and you’ll have a healthy compost mix.

The lasagna method is an excellent way to incorporate cardboard into your composting routine, as it ensures an even distribution of materials and promotes a healthy balance of carbon and nitrogen.

How to Compost Cardboard in a Worm Bin

If you’re into vermicomposting (composting with worms), cardboard can be a valuable addition to your worm bin. Red wigglers, a common type of composting worm, love munching on cardboard. Here’s how to use cardboard in a worm bin:

1. Shred or Tear Cardboard

As with regular composting, start by shredding or tearing the cardboard into smaller pieces. This makes it easier for the worms to consume.

2. Mix with Other Worm Bin Materials

In your worm bin, combine the shredded cardboard with other worm-friendly materials like kitchen waste and small amounts of yard waste. The worms will happily consume the cardboard as part of their diet.

3. Monitor Moisture Levels

Ensure that your worm bin maintains a moist but not soggy environment. Cardboard can help absorb excess moisture, but you should still monitor it regularly to prevent any issues.

4. Harvest Castings

As the worms consume the cardboard and other materials, they’ll produce nutrient-rich castings (worm poop) that make an excellent addition to your garden or potted plants.

Using cardboard in your worm bin not only benefits your compost but also provides a food source for your worms, keeping them happy and active.

How to Incorporate Cardboard for Sheet Composting

Sheet composting is another way to utilize cardboard effectively in your garden. This method involves laying sheets of cardboard directly on your garden bed to suppress weeds and improve soil quality. Here’s how to do it:

1. Prepare the Garden Bed

Clear the area where you plan to plant or improve the soil. Remove any existing weeds or debris.

2. Lay Cardboard Sheets

Place sheets of cardboard directly on the cleared soil. Overlap the edges to create a weed barrier. You can use large pieces of cardboard for this purpose.

3. Add Organic Matter

On top of the cardboard, add a layer of organic matter such as leaves, grass clippings, or compost. This provides nutrients and encourages earthworms and other beneficial organisms to move into the area.

4. Plant or Mulch

If you’re planting, make holes or slits in the cardboard to accommodate your plants. If not, cover the cardboard with a layer of mulch to improve aesthetics and moisture retention.

Sheet composting with cardboard is an effective way to enrich your garden soil while suppressing weeds naturally. Over time, the cardboard will decompose, leaving behind nutrient-rich soil.

Safety Considerations and Environmental Impact of Composting Cardboard

While composting cardboard is an eco-friendly practice, there are some safety considerations and potential environmental impacts to keep in mind:

1. Harmful Chemicals

Some cardboard may contain harmful chemicals, particularly in the printing inks. Be cautious about composting cardboard that you suspect has heavy inks or coatings. It’s always better to err on the side of caution and avoid composting cardboard with unknown or potentially harmful elements.

2. Methane Emissions

If cardboard ends up in a landfill, it can contribute to methane emissions when it decomposes anaerobically. Composting cardboard at home prevents this release of harmful greenhouse gases.

3. Recycling vs. Composting

While composting cardboard is an excellent way to reduce waste, it’s also important to prioritize recycling when possible. Recycling cardboard saves energy and resources compared to composting. Reserve composting for cardboard that cannot be recycled due to contamination or other factors.


Composting cardboard is a fantastic way to reduce waste, enrich your garden soil, and contribute to a more sustainable environment. By following the steps outlined in this guide, you can safely and effectively incorporate cardboard into your composting process. Remember to choose the right types of cardboard, shred or tear it into smaller pieces, and maintain proper moisture levels for optimal results.

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