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Touring the Casella Recycling Plant

On Wednesday I went on a tour of the Casella recycling plant. Cambridge’s recycling director, Randi Mail, is hosting tours before the town switches over to single-stream recycling October 25. Casella is already handling single-stream loads from many towns in Massachusetts, including Boston. It was fascinating to see the elaborate sorting process.

First, giant piles of recyclables are dumped off the trucks and bulldozed onto a conveyer belt, which levels them out into more manageable amounts.

The front of the warehouse, where trucks unload.

A teeny tiny bulldozer pushes the recyclables onto a conveyer belt.

Then the mass of recyclables are spun around a tunnel with 1-inch holes in the sides. Centrifugal force holds lighter materials to the side while glass falls to the bottom and shatters, over and over again, until it can fall through the holes.

Heavier metals (like pots and pans) and rigid plastic (like laundry baskets) are pulled out by hand and dropped into chutes. More than 20 people are stationed at various spots on the line to hand sort, but 99% of their job is to pull out plastic bags before they can gum up the works.

Workers pull out things that can't go through the line.

A magnetic conveyer belt runs over the line to pull out metal. Since aluminum isn’t magnetic, a later spot in the line reverses the polarity of the aluminum to repel it over a barrier and onto another belt.

An idea of the scale

Paper and cardboard slides up rollers spaced at intervals. The paper glides over the top of the rollers, but heavier materials like plastics fall through.

It's amazing how well sorted everything is by the end of the line.

Eight sets of optical sensors ID different kinds of plastics and trigger jets of air to shoot them over a barrier onto another belt.

One of the optical sensors

The end results are baled for transport. The system works remarkably well: the plant director told us that their buyers only allow 2% contamination of each material with another, so it has to be well sorted. Anything that didn’t get separated is run through the system again to capture as much as possible.

Bales of recycling are stacked way over your head.

I expected the warehouse to stink, but it didn’t. I guess that’s a testament to how well people rinse their recyclables. But it was very noisy and very dusty. And hot! I guess an 80-degree day wasn’t the best for a tour.

Some take-aways for me:

  • Plastic bags are death to the machines. The line is only running about 70% of the time, mostly because of plastic bags. So don’t toss them into recycling bins.
  • Plastic smaller than 3 inches falls through and doesn’t get recycled. So bottle caps should always be put back on their bottles.
  • Paper attached to glass gets thrown away, because tiny glass particles stick to it at the plant. So if you want to recycle it, pull it off at home.

If you’re interested in going on a tour yourself, Cambridge is hosting two more this year, on October 28 and November 18. To sign up, email or call 617-349-4815. If you can’t make the tour, you can also watch a video about single-stream recycling on Casella’s website.

One year ago: Revolving Doors.


Comment from Alison
Time October 1, 2010 at 2:31 pm

Really fascinating!

Pingback from Pragmatic Environmentalism
Time January 19, 2011 at 12:07 pm

[…] may remember from my recycling plant tour that plastic objects under three inches don’t get recycled because they fall off the conveyer […]

Pingback from Pragmatic Environmentalism
Time February 22, 2011 at 8:02 pm

[…] my tour of Casella Recycling? Want to go on one yourself? Cambridge residents can sign up for upcoming tours on April 13, May […]

Pingback from Pragmatic Environmentalism
Time May 19, 2011 at 10:38 pm

[…] They have a lot tighter footprint; they don’t branch out to the suburbs much at all. I think Casella has a like service in Vermont, but they don’t do food waste in […]

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