The World Cement Association recently held its first-ever global climate change forum, where industry leaders and scientists discussed strategies to reduce the industry’s carbon footprint. It will help inform the development of a climate action plan, which the WCA intends to release in September, aimed at outlining pathways for low-carbon cement production.
«The Global Climate Change Forum made clear the importance of stimulating innovation if we are to have any hope of achieving the Paris climate goals,» Bernard Mathieu, director of the WCA’s climate change program, said in a statement.
While industries of all kinds are exploring ways to reduce their carbon footprints, the cement industry—unglamorous as it may sound—is among the most significant to join the discussion.
Cement is the most widely used man-made material in existence—it forms concrete when mixed with water, and is used in the construction of everything from buildings and bridges to roads and sidewalks and all kinds of other infrastructure.
But while cement has largely shaped the modern built environment, it’s also a massive source of carbon dioxide to the atmosphere. It single-handedly accounts for about 7 percent of all global carbon emissions, according to estimates from the International Energy Agency. That makes it the second-largest single industrial emitter in the world, second only to the iron and steel industry.
It’s a problem that often receives little attention among the public. But concern among scientists is rising. As global population grows, some estimates suggest cement production could increase by as much as 23 percent by 2050. And some experts suggest that unless the industry substantially reduces its emissions, it could put the Paris Agreement’s global climate targets in jeopardy.
An April report from IEA and the industry-led Cement Sustainability Initiative notes that the industry, in its current form, is inconsistent with trajectories that would allow the world to meet a 2-degree Celsius temperature target. Reaching this goal, the report suggests, «implies significantly greater efforts to reduce emissions from cement makers.»
THE RACE FOR SOLUTIONS
Portland cement—the most widely used type of cement around the world, and the product specified in many modern construction codes—was patented nearly 200 years ago and has become an essential component of the built environment. In the years since, little has changed about the production process, according to Gaurav Sant, a professor of civil and environmental engineering at UCLA.
«There have been improvements in process efficiencies, but broadly speaking it’s not that different,» he told E&E News.
That’s a big problem for the climate, because the process releases large amounts of carbon dioxide. The industry’s huge carbon footprint partly stems from its high fuel requirements, which are mostly satisfied by fossil fuels. But more than half of its emissions—and perhaps as much as two-thirds, by some estimates—actually come from the chemical production process itself, which releases large amounts of carbon dioxide as a byproduct.
Portland cement is produced in large part with limestone, a type of rock that’s composed mainly of a chemical compound called calcium carbonate. To produce the sticky, binding cement, the limestone must be heated at high temperatures—around 1,500 C, according to civil and environmental engineering expert Claire White of Princeton University.
The intense heating process in and of itself, she noted, requires a massive amount of fuel. But it also causes the limestone to chemically decompose, leaving behind a compound called calcium oxide, which is used in the final cement product, releasing carbon dioxide gas into the atmosphere.
The specific formula used for cement, and the fact that it’s remained unchanged for so long, makes the industry an unusually challenging one when it comes to climate action. A commentary published last month in Science evaluated a variety of «difficult-to-decarbonize» services and processes. Tackling cement, it noted, doesn’t have a single solution—it will require a variety of approaches, including major changes in both the materials used and the manufacturing process itself.
The problem has drawn the attention of major international organizations in recent years, some of which are now advising the industry on ways to cut carbon. IEA’s April report contained a low-carbon technology road map, aimed at reducing cement industry emissions 24 percent by 2050. The report outlines a variety of strategies that could help achieve that goal—everything from alternative fuels to carbon capture technology to new chemical recipes for the cement product itself.
Research groups around the world are already tackling many of these issues. Some groups are working on chemical formulas that would reduce the amount of «clinker»—the substance that requires the heating of limestone—that goes into the cement.
White, the Princeton engineer, leads the university’s Sustainable Cements Group, which is working on ways to eliminate the need for clinker altogether. It’s possible to make cement-like products using other substances instead, she noted, including recycled byproducts from other industries, such as steel slag, fly ash from coal-fired facilities or certain types of clays. Treating these substances with special chemical compounds known as alkalis «can make the powders reactive,» White said, «and we can form similar building blocks at the molecular level compared to what’s in portland cement concrete.»
That said, there’s some debate about exactly how much carbon output is associated with alkali-activated cements, she added, which can sometimes make it difficult to compare with portland cement. It partly depends on exactly what type of alkali sources, and how much, are used in the process, and how far the materials must be shipped. Some estimates suggest the practice has the potential to lower emissions by as much as 40 to 80 percent compared with portland cement, White said.
Other experts have pointed out that concrete naturally absorbs carbon dioxide. It’s a slow process, but over the course of decades, it may be able to soak up a substantial amount of the emissions it put into the atmosphere in the first place via the limestone heating process.
A 2016 paper in Nature Geoscience suggested that the world’s concrete has been absorbing about 43 percent of those original emissions. There may be some ways to speed up or strengthen this absorption process, Sant noted—it’s an area his own research group is focusing on.
Steven Davis, an earth system scientist at the University of California, Irvine—one of the authors of the Nature Geoscience paper, as well as last week’s Science commentary—noted that concrete’s absorption potential implies that there may be ways to make cement production carbon negative.
If cement production facilities were all outfitted with carbon capture and storage technology, for instance, then a substantial amount of the emissions produced on-site could be stopped from entering the atmosphere. Later, the concrete produced would soak up even more carbon dioxide, which could eventually amount to a «net drawdown from the atmosphere,» he told E&E News.
While different research groups are focusing on different approaches, IEA’s technology road map suggests that reducing emissions quickly enough to help meet global climate goals will require a variety of strategies all working together. This is likely to be the most successful approach, according to White.
«There might be front-runners in terms of what can help or what we can use in the near future, but that doesn’t mean we shouldn’t be looking at more innovative materials down the line,» she said. «It’s not just one technology that we need to look at to combat the sustainability issues associated with the concrete industry.»
A LONG ROAD AHEAD
Despite the rising interest in research and development, there are obstacles to implementing the solutions. One of these is a lack of policy incentives to convince cement manufacturers to invest in new technologies.
«As far as the major producers, it’s not clear to me that it is a very big priority,» said Davis. «I don’t get the sense that they feel that it’s a market for potential disruption yet.»
Emissions caps or carbon-pricing systems are some of the most frequently discussed solutions. Still, even in places where such frameworks exist, problems can arise.
In the past, the European Union’s Emissions Trading System has been criticized for providing free carbon allowances to large polluters, including cement producers. A recent report from CDP, a U.K.-based organization that advocates for transparency about corporations’ environmental footprints, pointed out that «carbon regulation for the sector remains benign, with the sector in Europe continuing to benefit from surplus free allowances.» The report suggested that carbon prices may need to rise three to six times as much to spur the adoption of carbon capture and other innovative technologies.
There are other challenges. The cement industry is a highly conservative sector, Sant noted—and not without reason. The construction of essential infrastructure, like buildings and bridges, carries a great deal of concern about safety and high anxiety toward the introduction of newer, less-proven materials.
«Because we’ve used this material for as long as we have, there’s a lot of user confidence associated with it,» Sant said. This may have made the industry more resistant than others to innovation.
Governmental regulatory agencies may be similarly conservative when it comes to construction codes. In the U.S., Europe and many other developed nations, these codes are generally based on portland cement chemistry, White said. Using a different product for a construction project would likely require the approval of the appropriate regulatory body—which may not always be easy to come by.
«There’s active work going on in this area, to try and provide the information necessary to the codes organizations as to how they could augment the codes to enable for more innovation in construction materials,» she said. This means there’s a need for new ideas on how to reduce the industry’s emissions, while showing that these new products are safe.
While research interest is growing, progress in the private sector for now is emerging but may be slow-going.
CDP’s recent report evaluated 13 of the world’s largest publicly listed cement companies on their readiness for a low-carbon transition. It suggests that the companies’ emissions have been falling by about 1 percent annually, on average. But it notes that this is hardly enough to keep pace with trajectories consistent with a 2 C climate goal. The report also points out that investment in research and development, as a proportion of sales, is low compared with other industries.
Still, the World Cement Association’s recent climate change forum may suggest that the industry is beginning to push for more action. And the variety of different approaches that experts are exploring may help make the road easier.
«You don’t want to try and impose change overnight—you want to be able to stage change,» Sant said. «You want to be able to evaluate lower-risk and higher-risk pathways so that you really create a portfolio of solutions, rather than just one that fits specific things.»
Fuente: Scientific American