The thrilling future of gravel

Everyone knows that humble gravel is a bestrewed assemblage of fragments of crushed stone, but what if this ancient, in-demand construction material wasn't? What if gravel was plastic? 

That's the idea anyway, put forth by Sebastian Sajoux. The entrepreneur runs California-based Arqlite, which produces lightweight, plastic gravel.

"We've developed a unique tech that blends mixed plastics into a new compound that can be shaped into new things," Sajoux tells IE.

"If you make a very niche product that isn't in demand, you're in trouble."

"Usually, recycling encounters a bottleneck for the products" of industry, where demand for a commodity disappears, so the firm can't keep producing the product (because no one will buy it). "If you make a very niche product that isn't in demand, you're in trouble."

But gravel is always in demand, isn't it? And the world is never in want of more plastic, which is in constant need of rapid recycling. This is why Sajoux's company takes specifically un-recyclable plastic (among other types) and converts it into a high-demand commodity: smart gravel.

Can gravel be ... smart?

Arqlite brands its product as "smart gravel," but it's a type of aggregate material, just like others. 

To circumvent the industrial bottleneck that niche material producers face, Arqlite develops all of its smart gravel from a material that's free for anyone to take: un-recyclable plastic that can't be easily repurposed.

"We're taking the plastic that no one else wants."

"We don't have to pay for the plastic material we use since we take un-recyclables," Sajoux explains. "We're taking the plastic that no one else wants." So, while there are a few reasons a skeptic may roll their eyes at the idea of smart gravel, one can't disagree with the taking-plastic-nobody-wants strategy.

"We're competing with conventional gravel by offering an environmental incentive — and our smart gravel sells for $180 per cubic yard," says Sajoux. That's still more expensive than ordinary gravel, but Arqlite's smart gravel comes with desirable properties that conventional gravel doesn't offer — and the key is in the making.

Back up the trucks

"We get full truckloads of bailed plastics," explained Sajoux. "The recycling industry ordinarily separates and classifies the plastics, but we started to think of a different way and made it as diverse as possible.

"So now, if we get just a full truckload of polyethylene, we have to mix it with other things."

This means mixing un-recyclable plastic with other recyclables that Arqlite receives from clients. After this, the material is run "through a cleaning process — it doesn't use water, but it takes away all the dust and contaminants." In other words, there's no wasted water, and no new contaminating pollutants are released into the environment.

"It's a kind of centrifuge system that uses friction to get rid of any extraneous materials," Sajoux says. After this, an extrusion process heats the plastics, and this imbues the material with a trademark feature: "Not only does this process create a new blend or mix, but it also injects air bubbles — this makes the gravel very light and stable."

That lighter weight means a lower transportation cost and more durability on longer timescales than conventional gravel. Stone gravel is reduced to power; plastic gravel doesn't diminish similarly.

"We're using the best of plastic polymers — those are lightweight, compared to gravel," says Sajoux. "We're three times higher in volume compared to mineral gravel. ANd we're almost half the weight of expanded clay. Not only because of the plastic but because of the air we inject."

Who's in the market for truckloads of plastic gravel?

The uses cut across a much broader spectrum, Sajoux says. "We're selling it for big hydroponic farming," said Sajoux. Arqlite's "product could last 50 years, and that adds value for hydroponic systems. Water running through pipes, you want to keep it as clean as possible, so that's another added value."

Arqlite was also certified by the recently launched Recycled Material Standard (RMS), which is a "voluntary, market-based framework to ensure consistent labeling of products and packaging that contain or support certified material," according to a report from the venerable Recycling Today.

Arqlite can offer its smart gravel throughout a wider share of the recycling industry through bonds or certificates, which "tear down the limits and boundaries," said Sajoux. "We have firms all across the country who want to recycle plastics, and sometimes it makes no sense to send plastic to California (for example). This certificate says you can be on the other side of the world and have plastics you don't know what to do with but want to offset it."

Next steps for end-to-end recycling — Arqlite is also expanding. The world is about more than plastic gravel, after all.

"We've recently developed a new machine within our process ... capable of producing pellets to produce new plastic products," says Sajoux.

This means the firm can complete the circle of plastic recycling: "We're also making pellets from mixed plastics that can be used to make electronics or car bumpers. Up to 20 percent of our recycled plastic can convert in this way."

These compounding developments are helping Arqlite launch a new licensing system by the end of 2022. Other companies will be able to partner, instead of setting up more Arqlite facilities for them. 

Humble gravel, the ancient material used to build our world, has a fantastic future; it's plastic.