From bacteria to bricks: Microbes used for building materials

Researchers at the University of Colorado at Boulder have developed a new approach to designing more sustainable buildings — with help from some of the tiniest contractors out there.

In a study published in the journal Matter, engineer Wil Srubar and his colleagues described their strategies for using bacteria to develop building materials that live and multiply — and might deliver a lower carbon footprint, to boot.

“We already use biological materials in our buildings, like wood, but those materials are no longer alive,” said Srubar, an assistant professor in the department of civil, environmental and architectural engineering. “We’re asking: Why can’t we keep them alive and have that biology do something beneficial, too?”

You can’t buy these microorganisms turned bricks at a store just yet. But the researchers said their ability to keep their bacteria alive with a high success rate shows that living buildings might not be too far off in the future.

Such structures could, one day, heal their own cracks, suck up dangerous toxins from the air or even glow on command.

Today’s more corpse-like building materials, in contrast, can be costly and polluting to produce, Srubar said. Making the cement and concrete alone needed for roads, bridges, skyscrapers and other structures generates nearly 6 percent of the world’s annual emissions of carbon dioxide.

Srubar’s solution: Hire some bacteria.

In particular, he and his colleagues experimented with cyanobacteria. Under the right conditions, these green microbes absorb carbon dioxide gas to help them grow and make calcium carbonate — the main ingredient in limestone and cement.

To begin the manufacturing process, the researchers inoculated colonies of cyanobacteria into a solution of sand and gelatin. With the right tweaks, the calcium carbonate churned out by the microbes mineralized the gelatin which binds together the sand — and, presto, a brick.

“It’s a lot like making rice crispy treats where you toughen the marshmallow by adding little bits of hard particles,” Srubar said.

As an added bonus, such bricks would actually remove carbon dioxide from the air, not pump it back out.

The researchers also discovered that they could make their materials reproduce. Chop one of these bricks in half, and each of half is capable of growing into a new brick.

The new bricks are resilient: According to the group’s calculations, about 9 percent to 14 percent of the bacterial colonies in their materials were still alive after 30 days and three different generations in brick form.