Bringing biology to the bricks – real world details on how to farm building materials

A team of American researchers has developed a new type of bio-concrete that could redefine what we mean by “green buildings”.

The concrete, developed by researchers at the University of Colorado at Boulder, uses bacteria as a binder. This leads to material that can grow and even heal itself, much like a living organism.

“When we finally found a solution that brought the brick to life, it was truly an ‘aha’ moment,” Wil Srubar said in an interview with Bob McDonald on oddities and quarks.

Srubar is an assistant professor of engineering at the University of Colorado at Boulder and led the work.

Bringing bricks to life

Concrete is the most widely used synthetic material on Earth, but its production has a massive carbon footprint. The manufacture of cement is extremely energy intensive and releases large amounts of carbon dioxide. The United Nations Environment Agency has called for “draconian action” to reduce this footprint in order to limit global warming.

“In our system, we don’t use cement and we actually use an organism that feeds on carbon dioxide to make the materials,” Srubar said.

An ark made of living building materials, next to the bacteria used to make it. (CU Boulder College of Engineering & Applied Science)

In traditional concrete, sand and aggregates are bound together by cement.

In this biological concrete, photosynthetic cyanobacteria take the place of cement. Bacteria use carbon dioxide from the air to produce a limestone-like material that sticks sand particles together, creating sturdy building blocks.

“The photosynthetic cyanobacteria that we use take in CO2 and some nutrients, and they biomineralize,” Srubar said. “It’s similar to a process of making seashells in the oceans.”

“And so, in effect, it creates tiny limestone particles like glue in our brick.”

Srubar’s process was a little more involved than simply mixing a batch of sand and a bacterial culture. The team had to find the right growing conditions for the bacteria, which included appropriate levels of moisture and important nutrients, but the process was still slow.

The “living bricks” seen in their mould. (CU Boulder College of Engineering & Applied Science)

The ultimate key turned out to be the addition of a jelly-like polymer that increased the rate at which the bacteria grew and produced the lime glue.

A new way to craft building materials

Another advantage of using bacteria for concrete is that it can self-repair and replicate. Srubar’s team found that when they cut a brick in half, they could grow the broken brick in a mold by adding more sand and nutrients – cyanobacteria would proliferate on their own. They were able to continue to “grow” new bricks from broken fragments of their bio-bricks.

“So really, what we were demonstrating is a new way of making building materials,” Srubar said.

“Why not take advantage of something that is growing at an exponential rate that is multiplying and use it to make the materials we choose to build?”

A worker pours concrete. Cement is a carbon-intensive industry. (Behrouz Mehri/AFP via Getty Images)

Given that traditional cement production is responsible for around 6% of greenhouse gas emissions, the researchers hope that by not just replacing this bio-cement, it could one day significantly reduce the contribution of building materials. to global warming.

Srubar also sees potential future use of his technology to build infrastructure on other planets.

“If we were to build a whole new world, we wouldn’t be burning limestone to make cement and we wouldn’t be melting sand to make glass. I think we’d look to biology to help us grow the materials .with which we choose to build.”