Minerals in the new material are deposited not by chemistry but by cyanobacteria, a common class of microbes that capture energy through photosynthesis. The photosynthetic process absorbs carbon dioxide, in stark contrast to the production of regular concrete, which spews huge amounts of that greenhouse gas.
Photosynthetic bacteria also give the concrete another unusual feature: a green color. “It really does look like a Frankenstein material,” said Wil Srubar, a structural engineer and the head of the research project. (The green color fades as the material dries.)
Other researchers have worked on incorporating biology into concrete, especially concrete that can heal its own cracks. A major advantage of the new material, its creators say, is that instead of adding bacteria to regular concrete — an inhospitable environment — their process is oriented around bacteria: enlisting them to build the concrete, and keeping them alive so they make more later on.
The new concrete, described Wednesday
in the journal Matter, “represents a new and exciting class of low-carbon, designer construction materials,” said Andrea Hamilton, a concrete expert at the University of Strathclyde, in Scotland.
To build the living concrete, the researchers first tried putting cyanobacteria in a mixture of warm water, sand and nutrients. The microbes eagerly absorbed light and began producing calcium carbonate, gradually cementing the sand particles together. But the process was slow — and Darpa, the Department of Defense’s speculative research arm and the project’s funder, wanted the construction to go very quickly. Necessity, happily, birthed invention.
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