Cardboard is an excellent brown material to add to your compost pile, but make sure there is no extra packaging, films, tapes, or paint on it.
Ink is okay, but nothing with a glossy coating.
Satin-finish cardboards are made of powdered clay and are compostable.
However, laminated cardboard, which is covered in plastic, should not be added to the pile.
To get the most out of your cardboard, add extra water to release the carbon and reap the benefits of composting other organic waste.