Biomason Builds Concrete With Bacteria

A billion or two years ago, corals, brachiopods, and other sea creatures took carbon dioxide and calcium out of the seawater to build shells out of calcium carbonate, CaCO₃. They were little biological factories capable of building giant structures like coral reefs. When they died they would sink to the bottom of the shallow seas and become limestone.

About 200 years ago, Joseph Aspdin figured out how to reverse the process, cooking limestone and clay at high temperatures, which decomposes after the water and carbon dioxide is driven off, leaving calcium oxide (CaO). This reacts with other ingredients, silicates and aluminates, to make Portland cement. Mix that with aggregate and water, and the mixture crystallizes and glues everything together into concrete.

Making Portland cement is responsible for about 8% of the world's carbon dioxide (CO₂) emissions; about half comes from heating the limestone to 1450 C in the rotary kiln, and about half from the chemistry of converting CaCO to CaO.

Essentially we are taking the shells of tiny creatures, heating them until the water and CO₂ is driven off and we have the basic constituent glue, and then we are adding the water and CO₂ back so that it glues the aggregate together. (This is grossly oversimplified, read more here if you like chemistry).

This is where Biomason comes in. Developed by architect Ginger Krieg Dosier, her process skips the middleman and a couple of billion years, going right back to the source: bacteria making calcium carbonate in situ. Biomason's Chief Technology Officer, Michael Dosier (also an architect, as I am; this is so exciting to see architects taking the lead in this) explains to Treehugger:

"Biomason is redefining what it means to produce concrete from a foundation firmly seated in natural systems of circularity. We are addressing the three fundamental problems of OPC [Original Portland Cement] concrete by redefining the entire manufacturing process. Biomason’s biological production platforms produce concrete materials by combining aggregates (crushed rock and/or sand) with bacteria, nutrients, calcium and carbon sources. We leverage the metabolic energy of bacteria to convert calcium and carbon sources into strong calcium carbonate structures."

This is not dissimilar to what was happening in the shallow seas 2 billion years ago. The difference here is that Biomason is putting those naturally occurring little bacilli to work, binding their aggregate together.

"The process put simply is waste aggregate mixed with our microorganisms, pressed into shape and fed an aqueous solution until hardened to specification. Biomason’s process enables materials to be formed in ambient temperatures by replacing the curing process with the formation of biologically controlled structural cement. The flexibility of our platforms allows us to source calcium from a variety of sources including seawater, salt reserves, or even limestone itself. Similarly, carbon may be sourced from carbon dioxide or directly as biologically generated carbonate."

Because they are growing calcium carbonate directly instead of digging it up, cooking it and then reconstituting it, this saves vast amounts of energy and absorbs CO₂ rather than emitting it. The process takes a couple of hours rather than a couple of eons.

"Unlike OPC which requires the embodied energy of combustion to fuel the reaction, Biomason biocements rely on the metabolic energy of microorganisms that occurs inside of the material at the time of production. These microorganisms create complex structures that exceed the mechanical properties of OPC. "

And, because it is plain old calcium carbonate instead of the more complex calcium silicate hydrate that you get at the end of the reaction in traditional concrete, it is more than just recyclable, they are actually growing a resource.

"Finally, because Biomason biocement® is calcium carbonate, our materials contribute to the geological limestone reserves: at the product end of life that calcium carbonate is available for future biocement® production (recycling) or other natural uses as part of our planet’s ecosystem."

Currently, Biomason is producing BioLITH cement tiles in Durham, North Carolina, which are used in some high-profile projects like Dropbox's HQ. They have a Declare label from the International Living Future Institute so they can go into the greenest Living Building Challenge projects; where original portland cement emits a kg of CO2 for every kg of cement, Biomason biocement actually absorbs and sequesters CO2, its carbon positive.

The big question that I have is, will it scale? We promote wood construction because unlike concrete, it stores CO2, but is not without its issues. Imagine if one could put all those bacilli to work, sucking up CO2 while formed into buildings or bridges. Biomason is already working on marine cement, which makes total sense; it all happened in seawater two billion years ago.

I asked Michael Dosier about this and he was noncommittal, but did say that "we are excited about the future potential of Biomason's technology for the building industries biggest challenges." So I suspect that we will hear some very dramatic news in the not too distant future, and it could change everything.

UPDATE: after reading comments, added image with specifications.