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How many times can a piece of paper be recycled?

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The recycling logo "“ those three arrows going around in an endless loop "“ is lying to you. While glass and plastic can be recycled indefinitely (at least in theory for plastic, which is usually "upcycled" or "downcycled" into products that can't be recycled), paper only gets so many go-rounds through the circle of life.

On trash day, the paper in our recycling bins goes to a recycling center and then a paper mill, where it's put into vat called a pulper. The pulper, which also contains water and some chemicals, is essentially a giant blender and shreds the recovered paper into small pieces. The paper-liquid mixture is then heated so the paper breaks down into little fibers. The resulting mush is called pulp.

Contaminants are removed from the pulp by cleaning and screening. The pulp is cleaned in a spinning cone-shaped cylinder that separates heavy contaminants like staples. Screening is exactly what it sounds like. The pulp is forced through various screens to remove smaller contaminants like bits of glue.

Some recovered paper is de-inked, and some is not. De-inking can be done in two ways: washing or flotation. During washing, chemicals are added to the pulp to separate the ink from the paper fibers. The pulp is then rinsed with water and the ink is washed away. In the flotation method, the pulp is put in another water-filled vat called a flotation cell. Surfactants are used to loosen the ink from the pulp, and air is passed through the cell. The air bubbles float the ink to the top of the mixture and the resulting froth skimmed off the top.

The pulp is then beaten to separate large clumps of fibers and make the fibers swell so they're better suited for papermaking. At this point, if white recycled paper is being made, the pulp is also bleached to make it bright white (if brown recycled paper is being made, say, for industrial paper towels, the pulp doesn't get bleached).

To make the pulp back into paper, the recycled fibers are blended with new wood fiber (virgin fiber) to give it extra strength and mixed with water. A paper machine sprays the watery pulp in a wide jet onto a wire screen conveyor belt. As the pulp travels on the belt, water drains through the screen and the paper fibers begin to bond together. A series of press rollers squeeze out more water and heated metal rollers dry the paper, which, now finished, is wound into a roll that can be cut into smaller rolls or sheets.

Phew. As you can see, paper goes through quite a bit of abuse during the recycling process and each time recovered paper goes through the whole song and dance the individual wood fibers become shorter and more brittle and lose their strength. Paper industry folks say that the average paper fiber can survive recycling six to eight times before its short enough to slip away during the screening process.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Nick Briggs/Comic Relief
What Happened to Jamie and Aurelia From Love Actually?
May 26, 2017
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Nick Briggs/Comic Relief

Fans of the romantic-comedy Love Actually recently got a bonus reunion in the form of Red Nose Day Actually, a short charity special that gave audiences a peek at where their favorite characters ended up almost 15 years later.

One of the most improbable pairings from the original film was between Jamie (Colin Firth) and Aurelia (Lúcia Moniz), who fell in love despite almost no shared vocabulary. Jamie is English, and Aurelia is Portuguese, and they know just enough of each other’s native tongues for Jamie to propose and Aurelia to accept.

A decade and a half on, they have both improved their knowledge of each other’s languages—if not perfectly, in Jamie’s case. But apparently, their love is much stronger than his grasp on Portuguese grammar, because they’ve got three bilingual kids and another on the way. (And still enjoy having important romantic moments in the car.)

In 2015, Love Actually script editor Emma Freud revealed via Twitter what happened between Karen and Harry (Emma Thompson and Alan Rickman, who passed away last year). Most of the other couples get happy endings in the short—even if Hugh Grant's character hasn't gotten any better at dancing.

[h/t TV Guide]