Our built world is full of dirty secrets. So many of the things we imagine to have little impact on our environment turn out to be remarkably unsustainable. Concrete, bricks, asphalt—we encounter these materials daily without ever really giving much thought to the fact that they’re actually pumping huge amounts of CO2 into our air due to their energy-intensive creation processes.

But alternatives to concrete and brick construction aren’t super common. Mainly because concrete and bricks have engineered over centuries to be very good at their jobs. Increasingly, though, designers and scientists are experimenting with new materials that are structurally similar to concrete while being a helluva lot greener.

Peter Trimble is one of them. For his thesis project, Dupe, the graduate of the University of Edinburgh, investigated if it was possible to grow our building material instead of using intensive heat. “I thought, Is there an equivalent material that’s more environmentally friendly but structurally comparable out there?” he recalls. Turns out there is. All you need is some sand, bacteria, calcium chloride and a decent amount of urea to make it happen.

Trimble’s idea isn’t an entirely new. A team of synthetic biologists from Stanford and Brown are looking into if this material could be used to build structures on Mars, and a couple years ago designer Ginger Krieg Dosier started BioMason, a company that creates bricks made from the very material Trimble used in his project in order to uproot the construction industry.

Admittedly, Trimble’s end goal was a little more modest. For his final project, he created a squat stool that is capable of holding all of his 200 pounds, but even this simple outcome is a testament to the material’s potential uses. Of course, it’s important to keep in mind Trimble is not a scientist. “I’m trained as a product designer,” he says. “So there was a massive massive learning curve.”

He began reading scientific papers, consulting with geo-engineers and working out the kinks of his recipe in the lab, using beakers and science equipment, “That was all well and good but for a product design product I need to make it look like it could actually be realized.”

>A team of synthetic biologists from Stanford and Brown are looking into if this material could be used to build structures on Mars.

Trimble ended up designing a mini manufacturing unit, which looks uncannily like an at-home beer brewery kit. There’s a stainless steel container, a mixer from a food blender and a pump from a coffee machine. Using this setup, the sand is poured into the stool’s mold before the bacteria is added. This bacteria and sand mixture sits overnight to ensure the liquid gets deep in-between sand particles. The next day, Trimble adds the urea and calcium chloride solution. When it comes into contact with the bacteria, a bond is formed, creating a cement-like material.

The sandstone has some drawbacks. Without reinforcement, its around two-thirds as strong as cement. And Trimble says it would need to be developed to better protect against erosion and water damage.

But on to the really important thing: We know you're wondering, and no, Trimble didn’t actually use urine to build his stool— though he totally could have. “I didn’t particularly fancy setting a bin in my bathroom and getting my flatmates to fill it up with urine, so we skipped that one,” he laughs. “Technically it’s possible, but you would need like 100 liters or something, and that’s a lot of wee.”