Are pizza cardboards stained with oil still recyclable?



I was told some months ago that paper and cardboard recycling processes need clean raw material. In particular, paper stained with oil may be inappropriate to recycle, and should rather be thrown away.

Where I live we separate our waste between:

  1. glass
  2. paper, cardboard, recyclable plastic containers, metal cans
  3. garbage, that is, everything else

When I happen to have a used pizza box, it is often stained with oil.

As I am not aware of the chemistry that is at stake for paper/cardboard recycling, I don't know if I should throw the oily pizza cardboard in the recycling or the trash. More finely, how oily can the cardboard be and still be a good candidate for recycling?

Stephane Rolland

Posted 2013-04-08T17:53:28.893

Reputation: 400

3I find the lid of the box is often clean, so I rip that off and recycle it at least... it's a good question though; how much contamination is ok? – Highly Irregular – 2013-04-08T21:52:21.573

1Unfortunately, as much as we want to maximize our recycling, if a batch of recycled paper is contaminated then the whole batch will have to be discarded. So in this case it is better to be conservative when in doubt. – half-integer fan – 2013-04-10T23:09:16.113



According to Stanford University, soiled food packaging should not be recycled like unstained paper and cardboard waste:

Q: Why can't pizza boxes be recycled?
A: Pizza boxes are made from corrugated cardboard, however the cardboard becomes soiled with grease, cheese, and other foods once the pizza has been placed in the box. Once soiled, the paper cannot be recycled because the paper fibers will not be able to be separated from the oils during the pulping process. Food is a major source of contamination in the various paper categories.


Posted 2013-04-08T17:53:28.893

Reputation: 1 184

5It's a shame they don't provide a definition for what counts as soiled. Small amounts of contamination might be ok. – Highly Irregular – 2013-04-11T07:54:12.817


In Boise, Idaho, US they used to prohibit food-contaminated cardboard (and still sort of do), but recently, on the official Facebook page of single-stream recycling program they stated that pizza boxes can be recycled, so long the food residue is scraped off (greasy spots are supposedly fine). So, who knows. Maybe technology improved?

– theUg – 2013-04-30T06:02:56.163


it is worth noting that although you can't recycle pizza boxes as cardboard, this doesn't mean you have to merely throw them away either. They form an almost perfect barrier layer for sheet mulches for example and you can compost them otherwise keeping in mind that they are a "brown" (i.e. high carbon, low nitrogen) and therefore act as a bit of a nitrogen sink in the compost pile.

There are a number of strategies for doing this. The most simple (as I mentioned above) is sheet mulching where soil may be disturbed but then covered with something like pizza boxes, newspaper, and other high carbon barriers, then packed with various layers and then left to compost in place briefly before plants are planted in the composting material.

So just because you can't recycle it into more cardboard doesn't mean it is best thrown away.

Chris Travers

Posted 2013-04-08T17:53:28.893

Reputation: 5 716

1Local reuse is almost always better than transport for recycling. The exception being things like reusing high embodied energy materials (like aluminium or titanium) as filler where it's replacing low embodied energy material (usually rock or timber). – Móż – 2013-07-24T00:11:39.120


Our local recycling center now takes food-soiled paper products for use in their composting program. You might look into that and see if there is anything like this in operation where you live.


Posted 2013-04-08T17:53:28.893

Reputation: 811