Cement isn't something most people notice, even though we all depend on it every day. The most common type of cement is called Portland cement, or OPC (ordinary Portland cement). Portland cement is used to bind concrete, an essential component of roads, bridges, and buildings.
Cement production is also a big contributor to global warming. Manufacturing Portland cement requires heating limestone to 1,449 degrees Celsius (2,640 degrees Fahrenheit). The heating process uses fossil fuels, which release massive amounts of carbon dioxide into the atmosphere. Carbon build-up in the Earth's atmosphere causes global warming.
A company called Calera believes it has figured out a way to make cement that stores carbon instead of releasing it into the atmosphere. Calera combines flue gas released from power plants with seawater to make cement. This method of carbon storage is called carbon sequestration.
Today, Calera has a prototype plant in Moss Landing, on the coast of Monterey Bay, California. Flue gas from the natural gas facility is pumped into Calera's cement plant. The flue gas, filled with carbon dioxide, is combined with seawater from nearby Monterey Bay. Seawater contains calcium, magnesium, and other minerals, the same ingredients corals use to build reefs. Carbon dioxide from the flue gas and minerals in the seawater combine to make calcium carbonate. Calcium carbonate is the material that makes up coral reefs, as well as Portland cement.
The process of making calcium carbonate cement from carbon dioxide and seawater is called Mineralization via Aqueous Precipitation, or MAP. After the cement is made, the heat from the flue gas is used to dry the cement into powder. Calera plans to desalinate and sell the leftover seawater.
The idea for MAP was developed by Brent Constantz, one of the co-founders of Calera. As a graduate student at the University of California at Santa Cruz, Constantz observed how corals used carbon dioxide to make reefs. He thought that if corals could make cement this way, then perhaps humans could do it, too.
Using nature as a guide to build new technologies—like energy-efficient cement—is called biomimicry.
"Biomimicry is in some ways a very old, and in other ways a very new discipline," says Sam Stier, director of public education and conservation at The Biomimicry Institute in Missoula, Montana. "Leonardo da Vinci drew inspiration from the natural world for his flying machine concepts in the 1500s, and humans have no doubt drawn inspiration from the natural world for thousands of years."
Today, biomimicry is used in everything from medical technology to city planning and architecture. By studying nature, scientists have come up with new ways to fight harmful bacteria, and to construct buildings that can heat and cool themselves. Researchers are studying how plants store energy, to help design better solar panels. Biomimicry principles are used to produce more energy-efficient trains and cars, and to help manufacturing plants create products that use less energy and produce little or no waste.
Applying the principles of biomimicry means working with nature, and it all starts with asking the right questions, says Stier. "How does nature power itself? How does nature make things without creating waste, or toxins, or pollution? The neat thing is, those answers are right outside your door! With the right questions in mind, anybody can be inspired by nature’s genius to invent a better future."
In that way, the Biomimicry Institute and Calera are united, says Stier. "The Biomimicry Institute supports biomimicry education and Calera makes cement, but we share a vision for a world empowered and inspired by nature’s genius. Corals can teach us how to make cement without mining or emitting greenhouse gases, and the rest of the natural world can teach us a whole lot more."
In the meantime, Calera is looking at selling a mixture of traditionally made Portland cement with the new Calera cement. It is also expanding the business. In January 2011, China Huaneng Group, Peabody Energy, and Calera agreed to pursue development of a green coal energy campus in Xilinguole, Inner Mongolia, China.