MSU Researchers Exploring Cement Alternative Using Fungi, Bacteria
From bridges to skyscrapers, concrete is ubiquitous in modern, human-built environments. It’s durable and cheap but also a big contributor to climate change, and some of the materials used to make it are getting scarcer. Researchers at Montana State University are trying to develop a sustainable alternative with microorganisms.
At MSU’s Center for Biofilm Engineering, Assistant Research Professor Erika Espinosa-Ortiz walks over to an incubator filled with glass chemistry flasks.
“So all of our fungi and bacteria are growing here,” Espinosa-Ortiz says as she pulls out one of the flasks. Suspended in the liquid is a piece of metal with something growing on it.
"We have all sorts of fungi. Like this guy. You can see it looks completely different. This is black. This is a mold. Sometimes you can see black stains growing in your bathroom. It’s probably this kind. So we study all sorts of different fungi and we’re trying to see how they can be grown in different conditions for different purposes," Espinosa-Ortiz says.
One of those purposes could be an alternative to concrete. Mechanical Engineering Professor Chelsea Heveran says making concrete requires a lot of energy and resources, like water and sand, and is responsible for about eight percent of human caused CO2 emissions each year.
“The fact is our built world right now is built on concrete,” Heveran says. “We’re running into a situation of increasing resource scarcity; we need to grow, right? And climate change is a major concern, and the inputs into cementitious systems, like cement and concrete, are becoming increasingly rare.”
Heveran is leading an interdisciplinary team of MSU researchers to re-envision building and infrastructure materials by borrowing lessons from nature.
“We’re wondering if we can better use microorganisms like bacteria and like fungi to build building materials in a different way that have the potential to be reusable and to be recyclable,” Heveran says.
With a half million dollar grant from the National Science Foundation, the team is experimenting with an approach similar to the way human bone grows with minerals hardening around a living, fibrous scaffold.
“We have tested these with bacteria and we are in the process of testing with the fungus,” Erika Espinosa-Ortiz says, pointing to several large syringes tied to a metal frame. “We fill the syringes with sand. We have all sorts of different kinds of sand. This is coarse sand and then fine sand.”
Through tubes attached to the top and bottom of the syringes, the researchers pump in a liquid with a fungus, which grows thread-like, branching networks called mycelium. Adding nutrients, calcium and bacteria kicks off chemical reactions to form calcium carbonate, the main mineral found in seashells and pearls, which cements all the sand particles together.
Espinosa-Ortiz holds up a small white cylinder.
"So after a couple of days, you end up with something like this," Espinoza-Ortiz says.
The cylinder looks like it should be lightweight, but it's solid.
"It used to be this material," says PhD student Arda Akyel says. "So these tiny particles turn into this block."
Akyel gently shakes a glass container full of tiny ceramic particles.
Heveran says this process they’re developing with the microbes could be more sustainable than regular cement for several reasons.
“Once I break that cement into pieces, I have very, very limited ability to reuse those pieces for anything else, and I can’t grind it back down and just pour it as new cement. The neat thing about calcium carbonate is that we can potentially break that down and use it as new inputs into other building materials,” Heveran says.
She says making the cement alternative also uses less energy since it can be done at room temperature.
There are still a lot of unanswered questions, like whether this material will be as durable as cement on a larger scale and how the fungus will react around other materials, like metal and plastic.
But Chemical and Biological Engineering Professor Robin Gerlach is excited about the possibilities.
“If we were stepping out and guessing where we would be in 10 years, we would be able to design materials by knowing which organism to grow under which conditions to build the material in the shape and with the properties that we need,” Gerlach says.
Gerlach and another researcher on the team, Associate Professor of Civil Engineering Adie Phillips, have already used microbes in real world applications.
With industry partners they developed a way to use bacteria to seal hard to reach fractures in oil and gas wells. Because the bacteria are so small and grow in place, they can get into tiny cracks more easily than regular cement.
“And the reason why we care about sealing oil and gas wells and leakage pathways is because, one, the producer wants to collect that material. They don’t want it to be lost to the atmosphere because they want to be able to extract it and use it,” Phillips says. “The other [reason] is that, especially methane, is a more potent greenhouse gas than CO2, and so we don’t want that leaking to the atmosphere.”
Montana Emergent Technologies, a small company in Butte, has used the biofilm barrier technology to seal more than 20 oil and gas wells.
As the researchers exit the lab and pass by walls made of cinder blocks, Heveran says in the future, researchers may be able to figure out how to harness microorganisms so that they serve more than one purpose.
“So not just holding up the load of this building but maybe helping to clean the air or clean the water or perform any of these other functions that microorganisms might be capable of,” Heveran says.
But that’s down the road. For this two year project, Heveran says the team will focus on creating blocks that can be glued together with a biocement, taken apart and reassembled.