Taking a Bite out of Cement’s Global Warming Potential

Hardcore greenhouse gas (GHG) geeks will recall that cement is a huge source of greenhouse gas emissions, with approximately 1 ton of CO2 equivalent emitted into the atmosphere for every 1 ton of cement produced. Damn. Forget your carbon guilt from flying, people! Cement is responsible for 5% of the Earth’s CO2 emissions, and it’s the third largest source of greenhouse gas pollution in the US according to the EPA.

A new technique has the potential to change cement’s impact on global warming, and I wouldn’t be writing about them if there wasn’t a great business opportunity here as well. Calera has created a process for incorporating waste CO2 emissions from a power plant into the cement manufacturing process. His system sequesters a half a ton of CO2 for every ton of cement created.

Constantz used biomimicry, the process of looking to nature for design inspiration, to get his idea. Sea coral create marine cement as one component of the reef building process, and the coral combine calcium, magnesium, and seawater to make their tough-as-nails product. Constantz has figured out a way to mimic the same process using the spent CO2 as a material source. "We are turning CO2 into carbonic acid and then making carbonate," Constantz says. "All we need is [sea] water and pollution."

The Calera process will prevent CO2 from entering the atmosphere in two ways: it eliminates the need to heat limestone (the key ingredient in traditional cement), which is one of the main sources of emissions in the traditional stuff, and it sequesters CO2 in the cement. Scientific American 
explains the process in greater depth: 

Nor are there any limitations on the raw materials of the Calera cement: Seawater containing billions of tons of calcium and magnesium covers 70 percent of the planet and the 2,775 power plants in the U.S. alone pumped out 2.5 billion metric tons of CO2 in 2006. The process results in seawater that is stripped of calcium and magnesium—ideal for desalinization technologies—but safe to be dumped back into the ocean.

In addition to using otherwise unusable materials and sequestering all that CO2, Constantz estimates that his cement will be cheaper to produce than the mainstream stuff (retailing at $100 a ton instead of $110.) That’s before you start talking about the potential for selling carbon offsets based on the carbon sequestration. Before you start calling Constantz to ask if he needs seed funding, you should know that venture capitalist Vinod Khosla has beaten you to the punch, as he usually does.