QUESTION: Can shiny cardboard be composted?
ANSWER: Any cardboard or paper product can be composted, however, some shiny paper products may take longer to break down and can slow the decomposition process. Shiny paper products used to be made with natural materials, like kaolin, which would break down at the same rate as the other paper products in the compost pile.
Today, however, shiny paper products are often made with plastic-like polymers, which can take much longer to break down than other paper products. In general, it is okay to compost any paper product, but it might be smart to avoid composting shiny cardboard or paper to keep your compost decomposing at a quick pace.