The Bio-Block Spiral is a small, short wall, but it may be a bulwark against a giant threat: climate change.
The curved, mud-colored structure is part of the current Chicago Architecture Biennial, entitled “Rehearsing the Future.” Unlike the artists’ installations filling the city’s downtown exhibit halls, the Bio-Block Spiral rises as a tight 15-foot-tall circle of concrete blocks outside the entrance to an office building that’s away from the action. Perhaps that’s because the wall’s chief creators aren’t artists. They’re bacteria. More specifically, cyanobacteria, aka blue-green algae, aka pond scum.
The cyanobacteria has been cultivated, with the help of clever biotechnology, to make biocement. The gooey material is a carbon-absorbing alternative to Portland cement, the binder currently used to make nearly all of the world’s concrete. Portland cement is churned out from limestone fed into giant, fiery, fossil-fuel-hungry, carbon-spewing chemical plants and is the source of around 8 percent of the world’s climate-warming CO2 emissions.
The biocement that binds together the sand and stone in the concrete used in the Bio-Block Spiral, in contrast, is expressed by the cyanobacteria, which is farmed, like a tiny crop. Because cyanobacteria live and grow through photosynthesis, they absorb carbon rather than emit it. Concrete made with biocement instead of Portland cement flips it from climate toxin to climate tonic.
Though the Bio-Block Spiral exists to demonstrate a material, standing in its arc can feel surprisingly spiritual. I first saw the wall in pieces. In late August, I traveled from my Chicago home to the headquarters and skunk works of Prometheus Materials, a biotechnology startup outside Boulder. Prometheus is commercializing the biocement used in the wall, not the blocks nor the concrete. The company grew out of a research collaboration at University of Colorado between biochemistry and civil engineering labs developing low-carbon building materials from living organisms.
At Prometheus, I saw cyanobacteria growing in the bubbling aqua-green water of the company’s bioreactors. I saw the harvested biocement get mixed in with Colorado’s reddish sand and stone and extruded into molds for the brown blocks. The workshop had a familiar earthy, sweet, slightly fecal smell that I recognized from Midwestern farms. I walked through the room where ceiling fans were humming to dry blocks tagged for shipment to the Biennial.
Once the wall went up in Chicago, I visited it several times. First for the science and engineering, but then also to experience its wonder. Each successive visit feels more profound. Billions of years ago, cyanobacteria figured out photosynthesis, and exhaled the oxygen that gave Earth a breathable atmosphere and enabled terrestrial life. Now it may save the atmosphere we’ve wrecked.
A massive opportunity
Of course the Bio-Block Spiral is not a place of worship, it’s a business proposition. A big one. Prometheus raised $8 million in its first round of funding and will soon begin scouting for a larger investment. The scale of the opportunity boggles the mind. Each year, the world produces around four billion tons of cement which goes into 30 billion tons of concrete. Per capita, that’s nearly four tons of concrete a year for each of the world’s 7.8 billion people. It is, by far, the world’s most-consumed manufactured material. Though concrete and cement production are close to their all-time highs, and are producing historic highs in CO2 emissions, the world may just be getting started.
You may have heard that the world uses enough concrete to build a Paris every week or a New York every month. Think bigger. The World Economic Forum estimates that global production could grow by up to 23 percent by 2050. That might mean a doubling of the entire world’s built environment every four years. Much of that would be driven by the addition of the three billion more people projected to join us on the planet by 2060. And by the aspirations of four billion people who today have moved up into the world’s growing middle class. The U.N. estimates that the world will need two billion more homes by the end of the century.
Concrete isn’t just the world’s overwhelming preference for built places and infrastructure; it’s the only building material abundant and cheap enough to meet demand. (Wood? There can never be nearly enough.) Prometheus’ proposition is that it can help meet all those local needs, avert a planetary disaster, and grow a company big enough to serve the whole planet.
Prometheus is one of a small but growing number of companies pushing biologically produced alternatives to portland cement. The general approach is inspired by the ability of organisms to create hard materials like shells, exoskeletons, bones, and teeth. Tiny life forms can be particularly productive. The mountains around Boulder make that point. Much of the rock in the Rockies, and in other mountain ranges around the world, is limestone that was forged from the shells and other carbonate hard bits of organisms that populated the world’s shallow seas hundreds of millions years ago. The manufacture of Portland cement reverse engineers that natural history by decomposing limestone and driving out its carbon. Biomaterials build the way shellfish do, by just building and binding.
Biomason, an 11-year old biomaterials company out North Carolina’s Triangle Research Park, makes concrete blocks, tiles, and precast structures out of recycled stones formed with a binder produced by its own strains of non-photosynthesizing bacteria that nevertheless can be induced to produce calcite, i.e. limestone. Last year, the company secured $65 million in funding and a pledge from H&M to use its tiles in its stores. It’s gearing up tile production at a large facility in Denmark.
Minus Materials, another startup spun out of the labs at the University of Colorado, harvests limestone, which can be turned into cement, from coccoliths, super-abundant one-cell marine microalgae that surround themselves with limestone they also produce by photosynthesis. That limestone can be made into a material nearly identical to Portland cement, but without a carbon footprint.
Nearly every sector of the construction industry has ambitious goals to reduce their greenhouse gas emissions. The biggest trade associations for the cement and concrete industries have pledged to scale down their net carbon emissions to zero by 2050. Yet the path to net zero has been chaotic. There are literally hundreds of innovative startups and research projects developing new materials and ways to drive carbon from the sector, but none of the big players or industry groups, or the governments that govern the industries, has settled on the technologies to deploy en masse.
The nearly universal challenge the contenders face is growing to the enormous scale needed to make a difference without taking decades to get there. The plants of the world’s largest, most global cement manufacturers, including Swiss giant Holcim, have already driven down the emissions for any given volume of cement by between ten and 25 percent. But mere per volume reductions won’t spare the atmosphere at the rate cement use is projected to rise. The total cost of retrofitting the world’s 3,000 cement plants to reach zero emissions (estimates run as high as $3 trillion) opens the door for biomaterials.
On one of my early visits to the Bio-Block Spiral, I met Scott Duncan, the architect who designed the wall, and Loren Burnett, the CEO of Prometheus. They were thanking the Chicago union masons who donated their labor to build the wall and tested whether they could work as usual with the new biocement-based blocks. (The masons told Prometheus they liked working with the blocks, which are slightly lighter than conventional ones.) Duncan is a partner at Skidmore, Owings & Merrill, the big Chicago architecture firm famous for ambitious projects, such as the Burj Khalifa and One World Trade Center. SOM’s engineers had an academic connection to UC Boulder and the firm’s corporate foundation supported the university’s materials scientists before Prometheus was formed. When Prometheus launched, SOM was one of the investors.
“To really make a difference in reducing carbon and buildings,” Duncan says, “you have to do that in a frictionless way that makes it easy for people to adopt the technology. Think about Tesla, which created a luxury vehicle that was actually faster than those with a combustion engine. It was not a compromise to drive an electric car. It is an upgrade of what we would normally be driving. So in this case, the [Prometheus] block is nearly identical to a typical concrete masonry unit. Because it’s important to have that kind of frictionless implementation.”
Biocement offers other benefits. “The building sector overall generates around 40 percent of the world’s carbon emissions, not just from concrete,” Burnett says. He adds that recent tests show that, because it binds so tightly, biocement produces a concrete product that is 12 times more absorbent of sound, while reducing thermal transmission by 90 percent. “That allows builders to use less of other carbon-intensive materials.”
Prometheus is currently planning to test its material in Seattle for seismic stability. UC Boulder will use Bio-Blocks to repair some older masonry on campus. Burnett says the business model of the company is not to make blocks or even concrete. Instead, the company hopes to license the use of its biocement to materials companies who could make their own concrete with it.
Growing production to meet global demand will pose a huge challenge. A four billion ton yearly crop of biocement would be more than all the world’s rice, wheat, soybean, and corn crops combined. This obviously would require big swaths of land, preferably near water sources that Prometheus’ cyanobacteria farms could draw from. The world’s current commercial production of algae and microalgae (for biofuels in the U.S.; for food, animal feed, and cosmetics in Europe and Asia) is infinitesimal compared to what would be required to replace Portland cement with biocement. Competitive pricing is also key, but Prometheus claims its current small-batch product is getting close in cost to standard cement, and the combination of efficiencies of scale and carbon tax incentives could make biocement the cheaper option.
Prometheus does not claim to have all the answers, but this much is certain: The viability of biocement—as a business, as a balm to climate change—only works if the material is deployed at a vast scale. Building the production infrastructure to replace one of the world’s most-used materials is a tall order that will require the kind of existential drive and all-out commitment humanity tends to reserve for war. But what makes the Bio-Block Spiral so alluring is that it confronts the real threats, to life and the environment, by calling up the generative power of life. If Prometheus’ technology can scale up, it may become one of the key elements in the arsenal to save the world we know.