Compost is a recipe for regeneration.

The composting process gives organic matter a new life, turning carrot tops and coffee grounds into a nutrient-rich material that nourishes our gardens, farms and natural communities.

Food scraps turning into soil supporting a small plant.

Healthy compost helps our soils absorb and hold water, prevents erosion and protects against soil-borne plant diseases. It also acts a carbon bank by removing and storing carbon dioxide, the most common greenhouse gas emission, from our atmosphere.

On the other hand, organic waste that sits in landfills – useless and unable to break down – produces methane. This highly potent greenhouse gas contributes to our changing climate and warming planet.

Still curious about compost? Read Compost: A Multi-layered Solution.

In our celebration of soil, we bring you tips to make Boulder’s compost the best it can be.

Compost Quality Matters

It is important that we work together to create high-quality compost free from plastics, metals and other materials that belong elsewhere. When added to your compost bin, these pollutants have the potential to make their way into our soils and waterways.

Help keep our community’s curbside compost free of contamination.

  • Learn what goes in your curbside compost bin and know before you throw.

    When in doubt, consult Eco-Cycle's A-Z Recycling Guide.
  • Prevent microplastic contamination.

    The composting process causes plastics to fragment into tiny particles, called microplastics, that pollute our environment and bodies indefinitely.

    • Recycle milk and juice cartons in your single-stream recycling bin.
    • Remove stickers from fruit and vegetable scraps.
    • Throw plastic-coated paper plates, cups and takeout boxes in the trash.
    • Choose reusables instead of single-use packaging.
Red onion with produce sticker on it.

Be sure to remove produce stickers from fruits and vegetables before putting them in your curbside or backyard compost bin.

  • Look for Biodegradable Products Institute (BPI) certification.

    These products safe for our soils.

BPI Compostable Logo

Look for the BPI Certified Compostable logo.

These labels also mean certified compostable: ASTM D6400, ASTM D6868, ingeo, NatureWorks LLC and PLA 7

Be on the lookout for non-compostable look-alikes labeled with misleading words like "eco-friendly," "biodegradable" and "plant-based." Surprisingly, none of these phrases ensure that a product is compostable or safe for our soils.

Check out Eco-Cycle's Is It Compostable? guide for a longer list of contamination culprits.

Do not put these items in your curbside compost bin:

  • Pet waste and diapers.
  • Rubber bands, twist ties and mesh fruit bags.
  • Shredded paper mixed with non-paper material.
  • Any type of plastic bag.

Rule of thumb: only compost materials and products that were once alive and/or feature the BPI logo.

Three non-compostable coffee cups.

These coffee cups are lined with a thin plastic coating and do not have a certified compostable label, so they must be thrown in the trash. The single-use plastic lids belong in the trash too.

Four things you can compost in your curbside bin:

  • Low-grade paper like tissues, paper towels and wax paper.
    • Pro tip: scrape wax paper with a butter knife or fingernail. Compostable wax paper will show a line, while plastic-coated paper will not.
  • Dark and brightly colored paper.
  • Meat and dairy.
  • Greasy pizza boxes and other cardboard containers.
    • Make sure cardboard is not covered in plastic film, and remove any stickers or tape.
Empty greasy pizza box.

Greasy pizza boxes should be put in your curbside compost bin.

Practice Compost Sorting

Just starting to learn how to sort? Check out the city’s Zero Waste Sorting Quiz for an interactive and educational game. Already a sorting expert? Test your knowledge with Eco-Cycle's sorting game.