According to the U.N. Environment Program, 50 metric gigatons of greenhouse gases are released each year into the atmosphere—and without serious intervention, this number is likely to rise. Given the magnitude of the problem, any solution to society's accelerating carbon generation is welcomed, including technologies that actively remove carbon dioxide from the air. Widely publicized schemes involve the pumping of carbon into deep cavities below ground or at the bottom of the world’s oceans for long-term sequestration.
However, climate change–aware architects and designers know that the built environment can also play a role in reducing carbon emissions. Wood, for example, is the most familiar biologic carbon vehicle for buildings to embody carbon. For composite building materials, however, the story becomes more complicated.
Carbon sequestration in materials involves varying degrees of processing and chemical conversion. Unlike the geological-scale carbon dioxide–pumping technique, in which the gas is moved to large cavities underground (often in compressed liquid form), product-scale sequestration strategies store carbon as part of a material’s intrinsic composition. To address this, manufacturers have been exploring innovative carbon-management methods for concrete, given that it has the largest carbon footprint of any building material.
Piscataway, N.J.–based Solidia Technologies, for example, uses a low-emissions cement and cures concrete using only carbon dioxide—as opposed to water—resulting in a 70% reduction in the carbon footprint compared with typical concrete. To create its Solidia Concrete, the company mixes its proprietary cement with sand, and then adds a water and carbon dioxide mixture to fill the porous spaces between the aggregate. Ultimately, the cement reacts with the carbon dioxide, resulting in concrete. Any water used during this process can then be reclaimed. According to the company, this method “has the potential to eliminate at least 1.5 gigatonnes of carbon dioxide” and “save 3 trillion liters of fresh water” annually.
Newcastle, Australia–based Mineral Carbonation International applies the general process of mineral carbonation to create raw material feedstocks suitable for new cementitious products like concrete pavers or plasterboard. In this case, the company heats magnesium silicate rock, or talc, so that it releases water and combines readily with compressed carbon dioxide. The result is silica sand and magnesium carbonate, a non-toxic mineral used to produce bricks, fireproofing, coatings, and other products.
Berlin-based Elegant Embellishments, the manufacturer of the air pollution–reducing Prosolv façade system, has developed a building envelope module made of solid carbon captured from the atmosphere. The so-called “Made of Air” system consists of hexagonal, dimensional wall tiles that are fabricated by baking carbon-rich waste biomass in an oxygen-free oven. The grooved black modules offer a visual reminder of concentrated atmospheric carbon that, in this case, has been transformed into a reusable building product.
Other materials offer a less direct connection to carbon sequestration, yet are no less supportive of reducing atmospheric carbon dioxide. For example, Carbon4PUR—a European Union consortium project coordinated by Covestro Deutschland—transforms waste flue gas generated by steel mills into carbon- and CO2-based foams and coatings. One of the primary applications is rigid polyurethane insulation for buildings. The approach, which reportedly reduces the necessary processing energy for such a product by 70%, also measurably reduces the emissions of the steel mills that provide the flue gas as a resource.
At the University of Tokyo, chemistry professor Kyoko Nozaki has developed a method to create a new type of plastic from carbon dioxide. The novel material, called polylactone, is the product of carbon dioxide and butadiene—a gaseous hydrocarbon, employed to make synthetic rubber, that acts as a chemical binding agent. In Nozaki’s plastic, the fossil fuel-derived ingredients are reduced by 30% due to the incorporation of atmospheric carbon. Because materials like synthetic polymers are created by adding oxygen to hydrocarbons, “if we take oxygen from a material that has too much of it, the same product can be obtained,” Nozaki explained in a University of Tokyo press release. “Thus, it is theoretically possible to make these chemical products without using fossil resources at all.”
Glass has even been made from carbon dioxide. Scientists Federico Gorelli and Mario Santoro, both at the Florence, Italy–based European Laboratory for Non-Linear Spectroscopy, have created amorphous carbonia. Just as ordinary glass is made from silica and oxygen when melted and cooled, Gorelli and Santoro demonstrated a similar outcome with carbon and oxygen. Transparent and robust, the resulting material is similar to window glass. Unfortunately, amorphous carbonia is only stable when kept under intense pressure, so the material is not currently usable. Yet the scientists’ research is contributing further knowledge to the behaviors of, and productive uses for, carbon dioxide.
As these various examples demonstrate, new building materials—and by extension, the built environment—can contribute meaningfully to reducing greenhouse gases in the atmosphere. Buildings comprise a significant portion of the human-modified regions of the planet’s surface. They must, therefore, participate in a global effort to sequester carbon. “In order to reduce carbon dioxide in the atmosphere, we will have to consume it," the directors of Elegant Embellishments argue.
This article has been updated since its original publication.