Many people assume that they can recycle pizza boxes. In fact, most pizza boxes have recycling symbols on them and are traditionally made from corrugated cardboard. They are, in and of themselves, recyclable before they are used.
However, what makes parts of them non-recyclable is the hot, tasty treat that comes inside them, specifically, the oily crust, savory sauce, and greasy toppings and cheese that make the pizza great. They all soil the cardboard.
A pizza box — or any paper product — that is stained with grease or food is not recyclable unless you remove all of the soiled portions.
But why is this? And what are the implications for the general, pizza-loving public?
How Pizza Boxes Get Recycled
Food is one of the worst contaminants in the paper recycling process. Grease and oil are not as big of a problem in plastic, metal, and glass recycling, as those materials are processed using a heat process. But when paper products, such as cardboard, are recycled, they are mixed with water and turned into a slurry. We all know that water and oil don’t mix, so what are the implications for paper recycling?
Grease from soiled paper products causes oil to form at the top of the slurry, and paper fibers cannot separate from oils during the pulping process. Essentially, the oily contaminant ruins the entire batch of paper fibers. This is also why other food-related items are non-recyclable (such as used paper plates, used napkins, and used paper towels).
“The oil gets in when you’re doing your process of making paper,” said Terry Gellenbeck, a solid waste administrative analyst for the City of Phoenix. “The oil causes great problems for the quality of the paper, especially the binding of the fibers. It puts in contaminants, so when they do squeeze the water out, it has spots and holes.”
But what about other things regularly found on paper products, like ink? “Most inks are not petroleum-based, so they break down fast. Food is a big problem,” said Gellenbeck.
When recycling, do be mindful of adhesives that may be on the pizza box (like coupons and other stickers), as those are also contaminants. Known as “pressure sensitive adhesives (PSAs),” these can ruin a batch of recyclable paper just like as oil or food remains.
Don’t Be a Recycling Sneak
Many people admit to “sneaking” their pizza boxes into their recycling bin along with cardboard boxes and other recyclable products. Unfortunately, this does more harm than good as the contaminated cardboard could ruin the whole recycling batch.
In fact, recycling contamination is a big problem in the United States. The high rate of contamination in our recyclable materials is why, in January 2018, China stopped accepting most of the recyclables the U.S. had been exporting there for decades. Now, communities are scurrying to find enough U.S. recyclers to handle the extra load. In some cases, the materials that people are faithfully placing in their recycling bins are ending up in landfills.
So, What Do I Do?
The easiest remedy for your pizza box quandary is to cut or tear out the soiled portions of the box and trash them. If the entire box is grease-free, the whole box can be recycled with a clean conscience. But make sure it really is clean, without grease, food, or stickers; you don’t want to contaminate a whole load of recycling!
Instead of recycling, you may want to compost the pizza box, although the grease is still problematic.
“Even with oils, you shouldn’t compost [greased cardboard]. It causes rotting, you get more bugs and smell and it’s just not good for the plants,” said Gellenbeck. Note that some communities accept food-contaminated pizza boxes in curbside compost bins. Check with your provider if you’re not sure.
Most importantly, make sure you understand clearly what your local recycling provider accepts so that you avoid contamination in your recycling.
“It all depends on where your processor sends your paper, too,” said Gellenbeck. “If you can keep a particular thing like the food out, the plastics out, all those things that really shouldn’t be there, it would help.”
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Editor’s note: Originally published on June 15, 2016, this article was updated in July 2018.