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A reader recently asked, "What about those grease-stained pizza cartons? Who's to say whether the stain is too much or 'Oh, that will pass!' "

I did some research on this question and found a great response on the Earth911 website. In a nutshell, any part of the box stained with grease and food is not recyclable. Remove those parts of the box and throw them out. The rest can be recycled.

You are doing no favors to the recycling cause if you try to recycle soiled boxes. Here is why: When paper products are recycled, water is added to form a slurry. If this mixture is contaminated by grease (i.e. from pizza boxes), oil forms at the top of the slurry. Paper fibers cannot separate from oils during the pulping process and this results in paper with spots and holes.

Have you heard the expression, "one rotten apple spoils the barrel"? That's what happens to the recycling process from carelessness or laziness. The introduction of contaminants ruins the whole batch, which must then be discarded.

Contamination of this sort results in huge losses for the recycling industry. Some estimate the figure to be as high as $700 million per year. The losses stem from damage to machinery, disposal costs for non-recyclable material and wasted time, materials and efficiency.

Also, when you're examining that empty pizza box, get rid of any stickers or coupons adhering to the outside. The adhesives can be just as damaging to the recycling process as the grease.