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A crushed white recyclable paper coffee cup with a brown coffee spill.
Knowledge Base

How Clean Do Our Recyclables Need to Be?

Contamination from food residue and moisture makes our waste streams nearly impossible to recycle. Learn the key steps to keeping recyclables clean!

Ryan Deer | February 17, 2021


When you accidentally throw something away that’s valuable, why is it that you hesitate to retrieve it? Is it because it’s gross to dig in rotting food and filthy packaging? Or is it because you may believe the very thing itself will already be ruined?

This is the challenge of the U.S. recycling stream in a nutshell and what leads to 25% (or more) of our recyclables being lost and landfilled due to contamination—a total that would otherwise garner billions of dollars. 

The issue has been present since the inception of the inefficient process of single-stream recycling. On one end of the spectrum, there’s the case of the wrong types of recyclables—like plastics #3–7—finding their way into a stream. And then there’s contamination caused by our ignorance (or possibly laziness): the jambalaya of dirty containers and water-logged cardboard that we create in our dumpsters.

Americans are failing in a standard procedure of a circular economy. It falls on us—not “the next guy”—to rinse and prepare our recyclables properly for the dumpster or bin.

Combating contamination is crucial for making recycling work for everyone, and employing the skills and habits to do so is easier than you’d think. 

It all comes down to four steps, but first, you’ll need to understand the why behind keeping your business’s recyclables clean, ensuring the material’s value stays in your budget and out of the dump.

What is Contamination, and Why is it a Problem?

If you’ve ever experienced how hard it is to get the last scoop of the peanut butter out of the jar, separate wet pieces of paper, or find every shard from a broken wine glass—consider the people tasked with trying to recycle it.

As a basic definition in the waste industry, contamination is anything that significantly reduces the value of recyclable materials and renders them unusable. Commercial haulers depend on the resale value of your materials to turn profit, and when those materials are diminished, the haulers have no choice but to send it to the dump at their own expense. 

Worse, they’ll transfer that charge to your business by way of a contamination fee. It’s common practice...because we don’t learn from our mistakes.

[More from RoadRunner’s Waste Watcher’s blog: What is Recycling Contamination?]

Just one saucy container can contaminate an entire pickup of recyclables. And that’s because of something called commingling, the single-stream method behind both curbside and commercial recycling.

Like we mentioned above with jambalaya, by not keeping your recyclables clean, dry, and oil-free, you’re essentially the master chef responsible for a disastrous recipe. Half a bottle of soda, bacon fat on foil, well-saturated cardboard—all of it gets stirred up in your stream.

But why does residue or dampness make things like plastic and cardboard unrecyclable?

Illustrated paper sheets and a pizza box on a conveyor belt.

Let’s start with the items that stand to lose the most in a traditional recycling stream: paper and cardboard.

The big issue is integrity. Kept clean and dry, paper can be recycled four to six times, while cardboard can return five to seven times without considerable degradation in quality. This changes when thrown in with your soiled, damp, or sometimes moldy food containers.

Salad dressing (a natural enemy of cardboard) or even just a half-full bottle of water can spill, spreading to every dry item that’s floating free in your dumpster. When paper and cardboard become wet, the fibers can become brittle and crumbly, resulting in their recyclability falling close to zero.

Compounding this issue is how MRFs (materials recovery facilities) work. Paper and cardboard need to be lighter than the other materials that hit the conveyor belt, like aluminum and plastic. The facilities count on separating techniques like air jets, robots, and the basic laws of gravity—and when there’s water-logged, heavy cardboard in the mix, these methods fail.

[Infographic: Cardboard Recycling 101]

As a rule of thumb, paper and cardboard should be like Life cereal before the milk goes on; not the soggy, concrete mess when you let it sit too long.

Various plastic bottles and containers on a conveyor belt.

Aside from spoiling the party for paper products, plastics have their own issues with contamination, particularly oily residue and leftover food or beverages. Most plastic bottles and containers are rid of their contamination through a washing process at the MRF or are burned away when plastics are melted into pellets. But some contamination is inevitable, and it matters with the economy of plastic.

Virgin plastic, new resins created using zero recycled material and a natural gas-intensive process, is already cheap. When waste services try to sell their dirty recycled plastic, they’re competing in a beauty contest against the fresh stuff—and often take runner-up. With no takers, haulers cut their losses and dump that bale of sub-par plastics into the landfill.

That being said, there’s no need to run plastics through your dishwasher, and a single raindrop won’t doom your Amazon box.

How Clean Are We Talking?

The level of acceptable cleanliness is fairly straightforward. Ask yourself: How likely is this to spill? How much of it can get on other recyclables? How messy is the substance?

If the grease stain shows you exactly where your pizza was sitting in the box, it unfortunately needs to go in the trash. A quarter-sized spot? You can recycle that. 

If your stack of papers is already disintegrating into pulp, that’s a no-go. Some dry, crispy junk mail? Pitch it in.

If the plastic container is clear, you should be able to see through to the other side—plus, you can even leave the label on. Same goes for the aluminum can, minus the stuck-on SpaghettiOs.

Meanwhile, if there’s sitting liquid or your leftovers still in the bottom, that needs to go before you toss it. It’s not only guaranteed to taint the other recyclables in the stream, but food rots, dampness molds, and bacteria grows—a major sanitary risk for MRF facility workers.

Getting recyclables in a proper state of cleanliness will only take a moment, and we’ve broken it down into just a couple easy steps.

Four Easy Steps to Prepping Your Recyclables

1. Empty. Ensure that bottles, containers, boxes, and cups are cleared of food, liquid, and other bulk substances.

2. Rinse. To eliminate the majority of residue and oil-based substances that stick to plastic, aluminum, or glass, try running the item under warm water. (Skip this step for cardboard and paper.)

3. Swish. Once filled with water, a circular swishing motion is good for loosening up food debris or carbonation foam that would otherwise leach out. (Skip this step for cardboard and paper.)

4. Shake/Dry. A few droplets are fine, but shaking out, patting dry, or airing out your recyclables after a rinse is the best practice. Ensure your dumpster or recycling bin has a closed lid to prevent rain from ruining your work.

While this four-step process is effective for the majority of your recyclables, some particulars require a little extra effort. These include: peanut butter and mayonnaise jars, honey and molasses bottles, and the container from your takeout salad.

5. Scrape. For the most stubborn of residue, take a spoon, sponge, or flexible rubber spatula to scrape and squeegee off as much of it as possible.

With just a few moments of your attention, you’ll be able to turn trash back into treasure—or at least stop taking hits on your recycling bill for being sloppy.

At RoadRunner, we take it a step further for businesses. Our method, clean-stream recycling, cuts contamination from start to finish—and you keep a share of the treasure.





Let's get the conversation started on how to drive recycling and cost savings for your business.