A pizza box may be labeled as recyclable but once it is soiled, it cannot be recycled. According to earth911, food is one of the worst contaminants in the paper recycling process. Grease and oil are not as big of a problem for plastic, metal or glass, as those materials are recycled using a heat process. But when paper products are recycled, they are mixed with water and turned into a slurry. Since we all know water and oil don’t mix, the issue is clear.
Believe it or not, bright paper can stop a whole batch of paper from being recycled. The idea behind this one is simple, explains Dan Baril, recycling program manager at the University of Colorado, “It’s like the red sock in the white load syndrome.” If you need to buy colored paper, avoid really rich colors, and opt for pastels. Paper mills can usually handle the lighter tones.
Currently, paper coffee cups (also called hot cups) are accepted for recycling at only few communities in the U.S. The thin polyethylene plastic coating on the cups that helps prevent liquid leaking has made it difficult for most processing services to recycle the cups.