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Friday January 20, 2017
Posted: Apr 29, 2014

Plastic can’t take the heat

Under Current

When I started studying ocean plastics four years ago, I was a gung-ho recycler. I had lobbied to have recycling bins brought to our condominium. I was excited for all the different plastics I could put into the bins. I loved the very idea of “closed loop” recycling, bottle-to-bottle, reusing plastic endlessly. All the hype the plastics industry has heaped on us for years.

The trouble is, it’s bunk.

Plastic is not endlessly recyclable. It’s not even truly recyclable once. Why not? One word: Heat.

When you recycle steel or aluminum, you melt it down completely, skim off the impurities, and are left with 100% steel/aluminum again. It’s the same material, the same properties. It’s ready to go back into whatever the original items were -- cans or car frames.

Plastic does not return to its original properties after being remelted. It has a “heat history” -- becoming weaker & weaker with each re-melt. It loses its stabilizers, anti-oxidants; its molecular bonds break. A bottle made from 100% recycled plastic simply isn’t as strong as one made from virgin plastic.

This is why recycling plastic is so hard. You can’t heat it enough to kill pathogens and germs or melt away impurities. If you do, you ruin the plastic so it’s structurally unsound.

Milk jugs are #2 HDPE plastic. That material is among the most valuable recycled plastic in the world, because it has a number of second uses.

Great, right?

Well, no. Recycled HDPE is almost never re-used in food-quality bottling. It's extremely expensive to sanitize and sterilize without ruining it. Virtually all of the 851 million lbs of recycled HDPE in the US in 2012 (PDF file, p 9) had to be downcycled. Made into other, junkier stuff. Clear HDPE gets reused in laundry detergent or motor oil bottles; colored HDPE in piping, plastic lumber, pallets. Most of that material is unrecyclable, economically, a second time.

However many milk jugs you diligently clean, sort, and send off for recycling, it's very unlikely you’re ever drinking milk from any of that plastic again. It’s on the downward spiral.

Worse, because of recycled plastic’s “heat history,” it is considered unwise to create HDPE bottles using more than 25% recycled plastic. Look at detergent bottles at the grocery store for yourself. The cheap, major brands state 25% recycled material. (They usually state “or more,” but that’s squishy PR-speak. Underwriter Labs Standard 746D limits “regrind” of once-used plastics to 25% as a rule of thumb (PDF file, p. 15).)

What does this mean? It means that every 1 milk jug you recycle has to be turned into 4 detergent/oil jugs in order to use all of that recycled material.

4 new bottles for every 1 we recycle, in trying to be “green”? Impossible. There’s no way all of our recycled milk jugs could be used for downcycled bottles. So the industry had to create new markets. Plastic lumber, plastic piping, plastic railroad ties, plastic pallets -- many of those markets were virtually non-existent before the glut of recycled HDPE. And that’s the kind of stuff that fills our rivers and oceans after every natural disaster now.

The plastic recycling industry is not about helping us use less plastic. It’s about helping us use more.

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