When placed in a landfill, it takes approximately 2 months for cardboard to decompose. However, the time it takes may vary depending on how thick the cardboard is and how wet the conditions are. Decomposition may also be affected by coatings or laminates found on the cardboard.
When compared to other items commonly found in landfills, cardboard biodegrades very quickly. Some items, such as aluminum cans, take several decades to decompose. Disposable diapers and sanitary napkins can take more than 500 years to decompose. Many items are considered non-biodegradable since it can take millions of years for decomposition to occur, if it happens at all.