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Trying to decide what is and isn’t recyclable can be a bit confusing. Does anyone really understand all those numbered plastic recycling codes? But some items seem straightforward—like pizza boxes. They’re just giant chunks of cardboard. They have to be recyclable, right? Well, the answer is, actually, not always.

The Atlantic’s CityLab website recently received the question, “Can I recycle a used pizza box or not?” They spoke to Darby Hoover, senior resource specialist at the Natural Resources Defense Council, who said the short answer is no. According to CityLab, “Even if you remove the crusty cheese and sauce the slices leave behind, grease will have already soaked into the cardboard, ruining it for recycling.”

But wait, it’s not like the pizza box is inherently not recyclable: The grease is the culprit. So one little drop of grease is going to turn my pizza box from eco-friendly to garbage? Other sites contest this point.

Back in 2013, Gothamist asked the powers that be in one of the world’s greatest pizza cities about recycling the boxes.“Oh yeah, we'll recycle your pizza boxes,” New York’s Deputy Sanitation Commissioner Ron Gonen told the site. “If the grease seeps through to where you can see a big hole through the box, or if you leave a slice of pizza in there, yeah that's too much, we can't recycle that…. But if it's just some grease stains and no solid matter, you're fine.” For pizza boxes specifically, the sanitation department instructs: “Remove and discard soiled liner, and recycle plastic supporter in your blue bin.” Grease is conveniently, or confusingly, omitted—though they do later state that “soiled paper” is not accepted.

If you really want to be a recycling superhero, you can even separate the greasy cardboard from the good cardboard yourself. “Cut off or out the tainted portion of the box,” suggests the Science Center in Philadelphia.

Or just stop ordering pizza altogether. If you really want to be environmentally conscious, you should probably be stretching your own dough anyway.