It’s not surprising that water is the most consumed substance on Earth by volume. It is surprising that concrete is the second most. It is also one of the biggest contributors of greenhouse gases to the atmosphere. Concrete is composed of 10 to 15 percent cement, the production of which generates a lot of carbon dioxide — the cement industry accounts for up to a full eight percent of annual global carbon dioxide emissions.
Concrete is a fundamental building block for much of the infrastructure on the planet today, and its prominence continues to grow. Global cement production increased by 54 percent from 2000 to 2006, and in the developing world it continues to skyrocket. In 2012, China accounted for just under 60 percent of the world’s 3.6 billion tons of cement production, an increase of about 10 percent from the year before. The Fourth IPCC Report in 2007 found that global cement consumption is growing at about 2.5 percent a year, with India and the U.S. leading the way after China.
Over the weekend the immensity of the cement business — and the potential for large-scale mitigation efforts — came into full view when the world’s two largest cement makers, France’s Lafarge and Switzerland’s Holcim, agreed to a merger to create a company worth a $55 billion with a presence in more than 90 countries. According to a statement released by the companies, it will create “the most advanced group in the building materials industry:”
Both companies have pioneered sustainability and climate change mitigation in the industry and are committed to take it to the next level. LafargeHolcim would have an enhanced presence in the global building materials sector with a number one position globally across cement, concrete and aggregates and new opportunities to optimize production and commercial networks.
The deal, clearly in the interest of the companies looking to reduce risk and streamline operations, still needs approval from antitrust authorities in Europe, the U.S., and other regions around the world as the merger places them in a very dominant position in many markets. Both companies have made previous efforts to reduce carbon emissions related to cement production, and if the merger goes through they would have an even more influential platform from which to address infrastructure sustainability issues.
The production of cement releases greenhouse gases both directly and indirectly. The production of clinker, the primary component of cement, emits carbon dioxide through the calcination of limestone. When limestone, which is made of calcium carbonate, is heated, it breaks down into calcium oxide and CO2. This accounts for about half the emissions attributable to cement production. The bulk of the other half comes from the energy-intensive process of grinding the raw materials and processing them into cement. The electricity used for this often comes from coal-fired power plants, which are heavy greenhouse gas emitters. Transportation of materials and operation of machinery accounts for about five to ten percent of the industry’s emissions.
As developing countries become more environmentally conscious and research into sustainable practices and renewable energy proceeds, there is great potential for continued and more substantial mitigation efforts from the cement sector. One area of opportunity is replacing clinker with other mineral components. Holcim has been working to incorporate fly ash, a waste material from coal-fired power plants, and slag, a waste by-product of steel manufacturing, into its product portfolio as composite cements. Lafarge is also making efforts to improve efficiency across production, replace dirty fossil fuels with more sustainable energy forms such as biomass, and promote sustainable construction initiatives.
“A lot of the cement and concrete industries’ significance to greenhouse gas emissions is just due to the sheer amount that is sold,” said Jeremy Gregory, an engineer who studies the economic and environmental implications of materials and executive director of the MIT Concrete Sustainability Hub.
Gregory told ClimateProgress that while a lot of effort is going into trying to reduce the emissions from the production process itself, it’s also important to consider the environmental footprint over the course of the lifecyle of the structure. For instance, most of the emissions from a concrete building come during the in-use phase and not the construction phase, so design elements that reduce energy intensity can be especially effective at reducing GHG emissions.
“It’s not going to be one thing that will solve the problem,” said Gregory. “By taking the lifecycle perspective, we are trying to emphasize that before you push one option you need to really consider the impacts of the lifecycle.”
For instance, fly ash can work like cement in gluing the rocks together in concrete. This is great because fly ash has already been used for something else and is being recycled. But if using it makes a structure that’s less durable than pure cement and the building collapses in half the time as it would have otherwise, then nobody wants that.
A recent article in Wired Magazine proposes that carbon capture and storage (CCS) may be one of the long-term options for limiting greenhouse gas emissions from the cement sector, where alternative power sources to fossil fuels are not yet viable. “In theory, coal could be replaced,” Barry Jones, a general manager of the Global CCS Institute, told Wired. “But that would involve rebuilding every cement plant in the world.”
With these considerations in mind, the European Cement Association estimates that a 32 percent reduction in CO2 emissions could be achieved by the cement industry by 2050. This is far below the 80 percent reduction suggested by the European Commission, and the organization is relying on breakthrough technologies, such as CCS, to close the gap. “According to the calculations, 81Mt of CO2 will still need to be eliminated,” the organization states. “It has therefore been assumed that 85 percent of total clinker production (equivalent to 59 percent of cement plants) will need to be equipped with, for example, carbon capture and storage technology.”
Concrete is typically made with cement, water, sand and gravel. Water is the most consumed substance on Earth, but sand is also in limited supply as infrastructure demands for it continue to grow. According to the U.N., annual use of sand and gravel combined is between 25.9 and 29.6 billion tons, enough to build a concrete wall 27 meters high and 27 meters wide around the equator. As easily accessible, inland deposits of sand are depleted, mining and dredging is occurring in ecologically fragile areas, leaving lasting environmental scars. The concrete industry has a long way to go to both limit its global impact on climate change through greenhouse gas mitigation and minimize local impacts associated with resource extraction and air pollution related to energy use.