QUESTION: Can you use cardboard for compost?
ANSWER: Despite what you may have heard, it is perfectly fine to compost cardboard trash—even if the cardboard is shiny because it’s covered with a gloss coating. When you do include cardboard in compost, though, there are a few things you need to know—there are troubleshooting (or rather, trouble preventing) steps that you’ll need to take to keep the cardboard from causing issues in your composting.
Cardboard tends to be less effective at maintaining the appropriate moisture level than the rest of the components that people use in compost. Shiny cardboard especially has trouble holding onto its hydration because the glossy top layer that’s responsible for its sheen functions as a barrier to keep water from ever being thoroughly absorbed.
In other words, cardboard is out of equilibrium with the other elements of the compost heap when it comes to moisture level from the very start, from the moment when the water is first applied. To restore harmony, you’ll need to take matters into your own hands and help the cardboard along by wetting it down generously right before you throw it into the mix.
Cardboard (especially when it has that slick top layer) is likely to take a while longer than most of your other composting ingredients to complete the process of decomposition and fully break down. This is an easy puzzle to solve, though. You can bring things into balance without a fuss, and do it efficiently, while you’re adding the cardboard to your compost pile, just by tearing any cardboard you include in your compost into small chunks so it will be broken down by the microbes in your compost more quickly.
Warning! Cardboard is extremely carbon rich, so you can’t add too much or it will bring the composting process almost to a complete stop. Use limited amounts and make sure you have plenty of nitrogen rich materials to balance it out.