Low-carbon concrete: Is the future now?

Concrete is the second most widely used material on Earth, behind only water. But concrete has also historically been detrimental to our environment. According to a study published in 2019, the combination of the calcination during the making of concrete, which in many locations uses coal or natural gas as the primary heat source, as well as the transportation of concrete, are major reasons why concrete contributes upwards of seven percent of global greenhouse gas emissions globally per year.

“If the cement industry were a country it would rank as the world’s third largest emitter of greenhouse gases,” said Eric Miller, director of New Jersey energy policy for NRDC (Natural Resources Defense Council).

Concrete has been in use for over 5,000 years, and for most of that time, not much has changed in terms of its environmental impact. But might concrete’s negative characteristics become a thing of the past?

The phrase ‘low-carbon concrete’ has entered the lexicon over the last few years, part of an overall move in all areas of the construction industries to produce less carbon-intensive materials and also to lower the carbon output of the construction processes themselves. A major part of this is all aspects of concrete, because it remains one of Earth’s most versatile, strong, and affordable materials.

Low-carbon concrete looks at the entire life cycle of the product. A heavy burden is in the making of the concrete, but also in the transportation and in other areas. As the National Resources Defense Council wrote in A Design Guide to Low Carbon Concrete Procurement for State and Local Governments:

Emissions reductions in concrete can be achieved cumulatively throughout the material’s full life cycle, not just through a single change. This includes via component selection; manufacturing, transportation, and construction processes; and post-construction maintenance, repair, and disposal or reuse.

At COP27, one of the more significant announcements was that the concrete and cement sectors would join First Movers. First Movers Coalition is an initiative that has 65 members (companies) who have committed to clean tech, and in 2022, concrete and cement joined aluminum, shipping, steel, trucking, and aviation. Major companies like GM and PepsiCo have joined First Movers.

At COP27 Shilpan Amin, the senior vice president and president of GM International, noted that in Tennessee, a GM plant had already begun to use carbon capture technology in its EV facility. And Mafalda Duarte, CEO of the Climate Investment Fund, noted that developing countries are some of the places where industrial emissions are at their highest, saying, “This is why I was particularly pleased that concrete and cement have joined the First Movers Coalition, because these products are in high demand in developing countries.”

First Movers is a private industry consortium. But there has been plenty of movement on the legislation side, as well, to help make the concrete space more environmentally friendly. Some of the most significant are the climate investments that were rolled into the Inflation Reduction Act of 2022. Included in this is money towards a new DOE venture called “Advanced Industrial Facilities Deployment Program” which will dole out grants for companies to retrofit and upgrade their operations. There is also the much-heralded Buy Clean Initiative, which directs agencies to purchase green building materials for their projects.

According to Construction Dive, the funding in the bill includes:

The author writes:

While there are alternatives to cement, many are in early stages of development and the traditional Portland mix remains profitable. With the new federal funding, contractors can use lower-carbon materials at no extra cost and build their expertise in green construction.

One a more local level, states like New Jersey are also incentivizing low-carbon concrete. The New Jersey Assembly recently pass a bill that “would provide corporation business tax (CBT) credits and gross income tax (GIT) credits to concrete producers that deliver concrete associated with reduced greenhouse gas emissions for use in certain State funded projects.”

“This bill is a smart, pragmatic step to reducing emissions from the building sector while simultaneously providing a competitive market for New Jersey businesses,” said Ed Potosnak, executive director of the New Jersey League of Conservation Voters.

If we look at different states around the U.S., different low-carbon initiatives have been passed. Colorado now has the “Buy Clean Colorado Act,” and New York enacted legislation that creates a low embodied carbon procurement standard for concrete in public construction projects. Other legislation is under consideration in California and other states.

On the new tech side, there are a number of new breakthroughs that could help make concrete production a far less carbon-intensive process. CarbonCure’s technology embeds captured carbon dioxide into mixed concrete, becoming a mineral, and has been used in dozens of projects around the country, including at Amazon HQ2 in Arlington, Virginia. Sublime Systems makes a concrete that eschews the kiln entirely in favor of an electrical process to convert the limestone, a process that happens at room temperature rather than at the hot temp inside a kiln.

Another technology being studied is something called bio-cementation, which uses microorganisms to create the calcium carbonate that gives concrete its highly desirable binding and strength characteristics.

The technology that might see the most use in the near future is carbon capture, where the carbon from production is captured, stored underground, and either put back into the concrete to make it stronger, or saved for other uses.

Ars Technica recently published a detailed article on all sorts of new concrete tech, such as the electrification of the kiln, the alteration of raw materials, and alternative cements.

So it would appear that the concrete industry is in the early stages of the move towards a low-carbon future. How soon it gets there will go a long way towards determining how quickly the industry can chip away at that exorbitant seven percent greenhouse gas emissions figure, and make concrete production, an ancient technology that hasn’t really changed a whole lot over the centuries, into an industry friendly to the future of the planet.