Abstract architecture, empty concrete room interior with opening in ceiling, 3d illustration, blue sky background
Looking for a Breakthrough in Cement and Concrete
Guest author Robert “Hutch” Hutchinson is an RMI Senior Fellow.
The toughest climate challenges involve large global industries, with no good substitutes. One of these literally produces the material under our feet—concrete. Every year, each of us in the U.S. uses about one-third of a ton. Fast-growing developing countries use far more. Globally we produce over 4 billion metric tons of Portland cement per year—the key ingredient in concrete and responsible for the majority of its CO2 footprint—driving over 5 percent of total anthropomorphic CO2. RMI’s research on the topic reveals that, to have a chance of significantly shrinking the industry footprint and meeting our Paris goals, revolutionary thinking and significant disruption is needed—a Tesla for cement, as it were. The industry-sanctioned traditional levers are not enough. And the new cement has to be really cheap. We have found three important opportunities that might work.
WHY CEMENT AND CONCRETE ARE HUUUGE
Finding a new, broadly applicable solution will not be easy, because the world needs so much concrete. It is the most flexible, cheap, and universally used building material on the planet. The only thing we use more of globally is water. Total Portland cement volume—making up approximately 20 percent of concrete by weight (the other main ingredients are sand, aggregate, and water)—has more than tripled in the last 20 years (a growth rate of close to 6 percent per year), most of the growth being in China. As China slows, another wave of countries such as India, Turkey, and Indonesia may take over as growth drivers, plus the U.S. if needed infrastructure rebuilding takes off. Global cement production growth may stay in the 2–4 percent range for a long time.
New plants being built in developing countries are much more efficient than the oldest plants anywhere—and much better than the average in the U.S. (India’s national cement industry average CO2 emissions rate is 25 percent lower than that of the U.S.). However, the total improvements that the best companies are making—about 0.5 percent per year over the last few years—cannot come close to counterbalancing even their own growth. And not all players are really trying.
Standard Portland cement cannot be made without releasing significant amounts of CO2, which is done in two ways: through burning fuel to produce the very high kiln temperatures needed, and through a calcining chemical reaction that occurs when the limestone is heated. At the most efficient plants, 60 percent or more of CO2 released might be from this unavoidable chemical reaction. Although other natural or waste materials such as rice hulls, limestone, blast furnace slag, and some kinds of fly ash can be partially substituted for Portland cement, it is the very standardization of Portland cement into a small and specific set of high-performing global products that have helped it become so dominant. This standardization is a huge barrier for any specific substitute.
WHAT THE INDUSTRY IS DOING TODAY
Like any industry that has been around a long time, there are some well-established levers to make it more efficient and emit less. The problem is, they are voluntary, coordinated by the Cement Sustainability Initiative (CSI), and do not go far enough to do more than slightly slow the growth of industry CO2 emissions. The CSI recommends the following to its members and the global cement industry:
- Plants and transportation of raw materials and products can be made more efficient, both thermally and electrically, and the worst plants can be shut down.
- Plants can burn organic waste or biomass to heat kilns (as in Brazil, which may lead the world in low CO2 emissions related to cement production).
- Supplementary cementitious materials (SCMs) like fly ash can be used instead of some—and often quite a lot—of the Portland cement.
- Alternative lower carbon chemistries like magnesium oxide-based cement, using special additives, or simply more judicious and use-specific mixing can reduce the amount of Portland required to achieve specific properties of a concrete.
All of these are actively underway in some—but not all—of the world’s cement markets. Leading players have targets in place for emissions intensity, and use all these levers. However, progress has not been and can likely never be fast enough. This is partly because the industry focuses first and foremost on reliability and product quality, which makes introducing any change challenging, slow, and costly. There must be proof that new approaches work. What’s more, the industry is very asset intensive, having a lot of money sunk in plants and equipment compared with its revenues and profits. Changing plants is expensive, and industry cash flows are not enough to make those changes quickly and still satisfy investors’ or government owners’ cost of capital. Change is also slow because most new plants are built in the developing world—typically not a good place to try innovative approaches given the on-site expertise needed to ensure something new or different actually works. And finally, industry dynamics have sometimes kept things slow. For instance, few companies want to invest in higher efficiency and “greener” cement if cheaper “dirty” cement can be imported from another country without being blocked or taxed. Such “carbon leakage” is a particular problem in Europe due to its proximity to North Africa and the Middle East, which have no regulations and can ship product across the Mediterranean cheaply.
ACCELERATING CEMENT INDUSTRY CLEANUP
The industry, via the CSI, believes the answer to emissions is to use the levers when economical, but continue to emit a lot, and then use CO2 capture and storage. CSI members are funding capture and storage research, but there is currently no approach that does not add significant cost and risk. Outsiders are trying too. Some new research companies like Blue Planet, Skyonic, and Solidia are proving technologies where the concrete itself absorbs CO2, with some good progress in niches like pre-formed concrete products. Ideally some form of carbon capture will have good economics and can be pushed toward rapid adoption. But in the meantime, the world needs more good, economically viable options that actually reduce emissions significantly. We believe these can come from three different directions.
1. INCREASE END-USE EFFICIENCY
To lower CO2 emissions from concrete, the key is cement. Portland cement can be used more efficiently both by developing concrete formulas that use less of it and by designing buildings that use less steel and concrete. Concrete doesn’t always need to be “rich” in Portland cement. Recipes for concrete are locally driven due to the characteristics of the local sand and aggregate. Also, durability testing is not always reliable so builders use more Portland as “insurance.” Few materials scientists work on concrete, and those who do are often funded by industry and therefore may not research ways to significantly reduce the use of Portland cement.
However, a concerted effort to both better understand concretes and invent tools to accurately predict concrete properties based on recipes could identify and standardize ways to reduce the volume of Portland cement use. Research into how to change the structural design of buildings and infrastructure to use less concrete can also improve efficiency. Both of these approaches can have very significant impact, in a way that can travel very fast—via information.
2. EXPAND THE USE OF SCMS
Supplementary cementitious materials are a terrific way industry is already reducing its CO2 footprint, and the development of more natural or minimally processed ones would be a huge leap forward. Today there simply aren’t enough supplementary cementitious materials in markets that are willing to use them, and sometimes they sell for even more than Portland cement does. But new kinds of SCMs are indeed on the horizon. Technologies now exist that enable even processed silica (sand) or volcanic rocks to serve as highly effective cements.
Unfortunately, these technologies, which do not involve heating to high temperatures or releasing CO2, appear to be “trapped” today, with little or no helpful engagement from the industry. Rapidly scaled, they could significantly damage the existing Portland cement players, so the very people most able to test and leverage them instead choose to shun them, particularly in high-price Portland cement markets or import-only markets like parts of Africa. One example technology—mechanical activation—has been tested and developed for more than 20 years without effective engagement from the industry. But as the search to reduce carbon pollution intensifies, such technologies may soon see the light of day.
3. CO-PROCESS CEMENT WITH OTHER PRODUCTS
Cement making, ideally, can share its heat with other processes, like electricity or even steel. In a low-carbon world, we will have to be parsimonious about heating anything to high temperatures. In some countries making cement is already combined with incineration of some kinds of hazardous materials, and this trend will likely continue. Could this idea really be extended? In theory, yes. Possibly the most exciting idea involves high belite Portland cements, which have been tested in China in the Three Gorges Dam and other massive, high-strength applications, and at the University of Kentucky and MIT. Concrete made with these cements is particularly well suited to hot, humid climates and to water-limited situations because of the way it cures. The cements can potentially be made from coal-fired fluidized bed-waste materials, lignite plant waste, and other industrial waste streams. Many hope that a way to make the two products together will be developed. Such coproduction could provide a significant net benefit in energy use and CO2 emissions.
Some of these ideas may be farfetched for now. But the need to move fast is very (ahem) concrete. Since governments buy about half the world’s concrete, in light of the Paris climate agreements this need is extremely visible—or should be. Public sector and other customers should demand the industry move faster and try new technologies, and be willing to add their support. Targeted research efforts—and much richer application of measurements and information technology—could change this relatively backward industry from a clear climate laggard to a powerful climate leader.
Image courtesy of iStock.