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Can Clean Cement help fix the Climate Crisis?

Concrete is the most widely used building material in the world. But the production of cement, the main ingredient in concrete, causes serious damage to the environment. Large amounts of CO2 are released into the air as the mixture is heated to upwards of 1400 °C. Additionally, the harvesting of the limestone needed to produce cement damages the land left behind after quarrying.

Brent Constantz, who earned a doctorate in Earth Sciences from UC Santa Cruz, thinks he may have a solution. He's started a company whose aim is to produce cement in an entirely new fashion.

Incredibly, at least to me - his plan is to make cement out of seawater.

That's a rather bold plan and one that could be fantastic if it works. Let's first look at how it came about.

The Basics

Wikipedia provides a detailed description of the production of concrete and cement. But for a clean, concise description, I like this one written by UCSC Professor Gary Griggs in the Santa Cruz Sentinel:

The primary ingredient of concrete is cement, which is produced from limestone. Limestone, or CaC03, is just the accumulation of the remains of millions of marine organisms that made their shells out of a few basic elements in seawater like corals do.

... limestone is heated up to over 1,800 degrees Fahrenheit, which drives off C02 and leaves lime or calcium oxide, the principal ingredient in cement. This process, however, releases one ton of carbon dioxide into the atmosphere for every ton of cement produced. Worldwide, about 2.5 billion tons of cement are manufactured each year, emitting 2.5 billion tons of C02, about 5 percent of the world's total C02 emissions

Note from the above that limestone comes from marine organisms.

A limestone-forming coral reef system.(US Geological Survey image by Curt Storlazzi)

The Problem

Cement production in the U.S. is the third largest source of greenhouse gasses domestically, according to the EPA.

As already stated, besides CO2, there's also "airborne pollution ... consumption of large quantities of fuel ... and damage to countryside from quarrying."

The Proposed Solution

I think what's fascinating about Brent Constantz's idea is not just the idea itself, but the steps in his life that allowed the idea to germinate.

Griggs points out that while at UCSC, Constantz was intrigued with the idea of how corals and other marine organisms can build their strong skins from the seawater they thrive in. That curiosity followed Constantz to Stanford University where he used his knowledge of marine exoskeletons to invent a cement for mending broken bones that was adopted worldwide.

Now, some 20 years later, Constantz wants to change the way industrial cement is made using some of the same principles.

While his exact technique is proprietary, his background hints at the process and suggests he's come up with an organic way to create cement that in effect cuts out the limestone "middleman" by using ocean water directly.

He set up his company, Calera, in Los Gatos, California and initially made trips over the Santa Cruz Mountains to obtain seawater to bring back to work, and develop his concept.

(photo credit: NOAA)
Now he's secured a "pilot factory" , a former magnesium hydroxide facility that made metal for World War II bombs" in Moss Landing, California.

Why did he want this site?

Well, as they say in real estate, location is everything. The plant is situated on the Monterey Bay, providing an ample supply of seawater. But equally important, it sits next door to a power generation plant. Why? Because strangely enough, Constantz's process requires the CO2 that the power plant generates.

Constantz takes that exhaust gas and bubbles it through seawater pumped from across the highway. The chemical process creates the key ingredient for his green cement and allows him to sequester a half ton of carbon dioxide from the smokestacks in every ton of cement he makes. (sfgate)

... His new cement mimics how coral reefs form, too. Coral uses the magnesium and calcium present in seawater to create carbonates much as he's using CO{-2} and seawater to make carbonate.

There's something quite significant in that first paragraph. Calera asserts that not only does this method eliminate the massive amounts of CO2 produced in traditional cement manufacturing, it also pulls CO2 waste from the power plant that would otherwise be released into the air.

Also eliminated would be the need for harvesting limestone and the related environmental problems.

"The beauty here is we're taking this old industrial polluting infrastructure and turning it into something that will save the environment," Constantz said.

Moving Forward

The company is working with the Monterey Bay Aquarium Research Institute and Long Marine Lab to determine what kind of environmental effects the process has on the ocean ecosystem. The company claims that the process actually makes the water "ideal for desalination," which some coastal communities are looking into to augment local water supplies.

There's still work to do to make this into a viable concept, both process-wise and economically. Calera could benefit from a cap-and-trade model where they could sell environmental credits for the pollution they eliminate. And of course, they still have the rather foreboding task of convincing construction companies (or cement providers) to use their product.

But as a study of how an idea germinates into something that has enormous potential, I personally found it fascinating.

And therein lies the rub. It’s a fascinating story. But is it too fascinating?

Green Cement or Greenwashing?

It seems that not everyone is convinced that the company has a viable product. The company has gotten good press in local newspapers, some of which I’ve quoted from above. Of course, the writers of those stories often tend to be feature-story writers and not science writers. (with the Sentinel story being an exception)

As our own RLMiller pointed out to me, “Calera is getting some positive press from the 'right' people -- ACI (American Concrete Institute) & World of Concrete.” They also got a good review from Scientific American.

But not everyone is convinced. Ken Caldeira, a scientist at the Carnegie Institution for Science's Department of Global Ecology has raised some questions, that can be summarized as follows:

• The scalability of the process is in doubt
• We won't know if net CO2 is saved unless Calera is much more forthcoming on all of the inputs and outputs

I also saw some rather scathing comments (from an anonymous poster) at a website I encountered in my research.

From a generalist perspective, it's hard to know what’s true and what isn’t. I can empathize with feature writers who write the story the company tells them, because it’s a very compelling story.

Like most things, the proof is in the pudding, or perhaps in this case the wet cement. Just as many of us choose to judge politicians by their accomplishments and successes, Constantz's plan to revolutionize the world of cement and its financial viability must ultimately be judged by real-world results.

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(Cross Posted at DailyKos:)

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