How Lego perfected the recycled plastic brick


EACH YEAR, MORE than 380 million metric tons of plastic is produced worldwide. Lego is responsible for 100,000 metric tons of it. This contribution to the annual total is, of course, the result of making its classic children’s toy. Lego’s impact may initially appear to be a sliver of that plastic output, but it still counts. Why? That 100,000 metric tons of polymer was last year turned into 110 billion bricks.

What’s more, the vast majority of those 110 billion bricks, as much as 80 percent, were made from acrylonitrile-butadiene-styrene, or ABS, a petroleum-based thermoplastic prized for its strength and rigidity. ABS does not like being recycled, because it loses those sturdy qualities. Such is the resilience of ABS, it takes lifetimes to break down, meaning whatever is made from the stuff will be hanging around on our planet for an awfully long time.

This is why, in 2015, after 66 years of pumping out vast quantities of unrecyclable interlocking toy bricks and perhaps sensing the impending plastic backlash, Lego announced it was putting $155 million of its huge income (2019 revenue hit $7 billion) into a new Sustainable Materials Center.

The first tangible product to come out of this center was a sugarcane-based plastic. It took the company two years to perfect this sustainable polyethylene, and it was hailed as a great success. The trouble was, due to its less-than-rigid nature, it was mainly suited to non-load-bearing lines, like trees and leaves—a tiny proportion of Lego products, around 2 percent.

Now, however, comes the main event: the humble 2 x 4 brick. Lego has moved on from bendy bioplastic to making a new prototype block that is fabricated from PET plastic from discarded bottles. It is the very first brick made from a recycled material to meet most of Lego’s requirements for its standard ABS bricks.

Over the past three years, Lego’s 150-strong Sustainable Materials team has tested more than 250 variations of PET materials. The resulting prototype, according to Tim Brooks, vice president of environmental responsibility at Lego, nails one of the toughest hurdles for a non-ABS brick: clutch power.

Clutch power is simply how well two joined bricks stick together. If a plastic is not rigid enough or shrinks too much in the manufacturing and molding process, the Lego blocks simply won’t grip to each other properly.

“We’re molding to the tolerance of about one to two microns, less than the thickness of a human hair,” says Brooks. “That’s incredibly precise compared to most consumer products. So the clutch is probably the number-one challenge we have. Either prototype bricks simply don’t hold or you’re using pliers to get them apart. To get that brick to mold effectively is hard. To go into the mold in about the consistency of toothpaste—pushing it in warm and then cooling it down – the material will shrink, you need it not to shrink too much.”

The brick also needs to not only hold its shape and keep that clutch but do so over entire generations of play, because Brooks says such materials creep and change shape over time. Standard Lego bricks are tested using high and low temperatures, butter, and even fake saliva to make sure they maintain their integrity over decades of use.

With its new PET brick, however, Lego has cracked it. Well, nearly. “We need to now work on how to slightly tighten the clutch and how to add colors to the brick,” says Brooks. “When we do that, we’ll go through shape by shape and determine how many ABS bricks can be replaced by PET.”

The key here is, out of the 3,500 or so different shapes Lego produces, the 2 x 4 brick is one of the most popular it. If the company can replace such a component with a recycled plastic version, it will have a significant impact of the environmental goal of Lego to be using fully sustainable materials in its products by 2030. “We have what we call ‘high runners,’” says Brooks. For example, we know that most sets will have a 2 x 4, certainly we know pretty much every set will have a 1 x 1 dot. That is by far the most common brick that we make.”

“ABS is incredibly stiff. Very stiff, very precise, very hard. PET is less stiff, less hard, and less precise, so that’s why we need to use an impact modifier with PET. That’s what different here. We are using a different grade of PET with an added ‘secret sauce’ that we have a patent pending on. So you’re looking at a PET that we’re modifying to make it perform like ABS.”

Gregg Beckham from the US Department of Energy’s National Renewable Energy Laboratory, who, in 2018 along with Portsmouth University’s John McGeehan, engineered an enzyme that digests PET, is impressed with Lego’s progress.

“ABS is an amazing material. It is extremely versatile, because you can change the ratio of the A the B and the S. And depending on how you formulate it there are a very large number of versions of ABS plastic that you can make. We literally touch it every day,” Beckham says. “PET, on the other hand, is challenging to formulate in a manner that has the same material properties as ABS like you would find in Lego brick. That is an exceptional polymer science challenge, for sure. This is super exciting.”

As for why it has taken so many decades of plastic production to get to this point, Beckham says that while it would be nice if we could wave a magic wand and just make it happen, in many cases the task is deceptively difficult. “This is fundamental material science and engineering that needs to figure out how to meet the same types of material properties with feedstocks that are either from recycled plastic or become recyclable themselves,” he says. “In the case of ABS bricks, they are neither from recycled plastics nor are they recycled at end of life. This potentially could meet both of those challenges simultaneously.”

There’s another benefit to the new prototype PET brick: It has a 70 percent carbon reduction compared to the virgin ABS material brick.

But, interestingly, while developing new eco plastics is ongoing, the real environmental benefits may well come from developing ways to recycle the stuff we currently can’t. Stuff like ABS. “Laboratory research today is thinking about using advanced recycling approaches that are able to break down the polymers, these long chains of molecules, into their building blocks,” Beckham says. “Then purify those and turn them back into either the same plastic they were at the same virgin-type plastic quality or to open-loop recycle them and turn them into something else that’s of even higher value.”

While this idea of recycling using chemistry to break down plastic like ABS is something that Beckham and his team are actively working, Lego has its sights set on this target too. As does Brooks. “We’ve use 20 different materials today; it may be that we end up with 40 in the future. Potentially ABS could be replaced by recycled ABS when we get there,” he says. “In the mid-term it will be recycled PET. We’ve got about 15 to 20 other materials that we’re working through one by one. But recycled ABS is where we’re trying to get to.”

This story originally appeared on WIRED UK., 11 July 2021