How scientists grow a sand-material that absorbs CO2!

Happy sand figure sitting in sand

A mix of sand, gel and bacteria can form a living construction material that absorbs carbon dioxide from the air, self-heals, and even grows on command. Nature is the source of inspiration!

It sounds a bit like science fiction, but researchers at the University of Colorado Boulder say that use of living building materials might not be too far off in the future. 

The material they present has extraordinary abilities. It resembles concrete but addresses two big concrete concerns – climate impact and freeze damages. 

Let’s start with sand. Reading here you likely know sand is a highly sought after material. Not only by sand enthusiasts as myself but by governments and companies all over the world. Sand is after water the world’s second most used natural resource. A big percentage of that sand is mixed with water and cement to make concrete for buildings and infrastructure. Production of cement, the “glue” in concrete, emit massive amounts of carbon dioxide to the atmosphere, which we all know by now, is bad for our environment.

Freezing and melting causes much damage to concrete and the number of freezing and melting cycles seem to increase with the current climate change. It’s common to add air bubbles in the cement to try to prevent freeze damage but this weakens the concrete. More sustainable alternatives are needed and the research team turned to Mother Nature for inspiration. 

“Nature has figured out how to do a lot of things in a clever and efficient way… We just need to pay more attention.” says scientist Wil Srubar, head of the Living Materials Laboratory and the science group. 

Two scientists in a lab inspecting a sand based living material sample
Wil Srubar and CU Boulder graduate student Sarah Williams check out a block made from “living” building materials. Credit: CU Boulder College of Engineering & Applied Science

Many fish, insects and plants thrive in sub-zero temperatures. Those that do can form an antifreeze agent that prevents ice crystals from growing. When the research team asked: How can we mimic nature? they came up with the idea of combining cyanobacteria, well known to survive in extreme environmental conditions with sand and a water-based gel. The result brings in a new perspective into construction combining biology, chemistry and engineering. Under the right conditions, cyanobacteria absorb carbon dioxide from the atmosphere and mineralize the gel binding the sand into a living material. The bacteria also grow and reproduce themselves. When divided a living material brick into two, each half was able to form two completely new bricks of the same size as the original one. Adding sand and water the team could grow three generations, making a total of eight bricks from one. 

Who would have thought that sand, super small rocks, could be a component to build a living material, yes a living material, that can absorb carbon dioxide?! That rocks! Cheesy as it is, but sand truly rocks. “The sky’s the limit with creativity,” Srubar says. Why not look down, we’ve got huge sand deserts out there filled with opportunities and ideas waiting to come!

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