Paper, which is made from the pulp of wood from trees, is generally considered a non-renewable resource because trees are being cut down faster than they can grow. Because paper is in such high demand in our society, paper recycling is important. Many types of paper can be ground back down to a pulp and remade into paper to be used again. But there are some kinds of paper that should not be recycled.

You should always throw dirty paper away in the trash, and never in the recycling bin. The city of San Francisco's recycling website lists pizza boxes, napkins, tissues, paper towels, paper plates and take-out boxes as common examples of unclean paper that should not be recycled. It's important not to get food in your recyclables because of the way paper is processed; it is mixed with water and turned into a slurry of pulp. If this slurry is contaminated with oil from food, it ruins the entire mixture and it must be dumped in a landfill instead of dried into new paper. Soiled paper also poses a health hazard to the people who work in the recycling plants who try to separate out contaminants. Old tissues, napkins and food can carry dangerous viruses, bacteria and molds.

Many people shred confidential papers to protect their privacy. Unfortunately, shredding paper shortens and weakens the length of the paper fiber, which needs to be long and strong in order to be worth recycling. Therefore, according to the Earth911 website, you should not put shredded paper in with your recycling. But the good news is that although you cannot recycle your shredded paper, you can compost it. It is necessary to add substances that are high in carbon and low in nitrogen, such as paper, to compost piles to offset nitrogen-rich decaying food so composting is a great way to reuse shredded paper.

Some items that are mainly composed of paper also have a small amount of wax, plastic or foil added to them, rending them not recyclable. Frozen food boxes, juice boxes, dairy milk cartons and soymilk cartons are specific types of these items, according to Earth911. The thin layer of foil lining the inside of soymilk containers, for example, is necessary to maintain its freshness, but is too difficult to separate from the paper during the recycling process. Carefully examine paper cartons that you are unsure of-opening them up to revel the insides if necessary-so that you do not accidentally recycle paper with one of these contaminates on it.