While cement is a major source of global emissions, many in the industry are hoping new innovations will usher in a greener future.
You don’t need to be an engineer or architect to understand just how ubiquitous concrete is. A quick glance around any town or city will illustrate why it is the most widely used man-made material on the planet; second only to water as the most used resource.
Cement is one of the ingredients that makes concrete – think of it as the ‘glue’ that holds the other ingredients (gravel, sand) together. Cement is so popular because it is remarkably good at what it does: it is reliable, durable and relatively cheap, and it can be produced anywhere. Production of cement has increased almost thirty times since the 1950s and almost four times since the 1990s. At the moment we make about 25 to 30 billion tonnes of concrete a year globally.
Builders have been using cement-like materials for centuries, with the builders in Syria and Jordan using cement-like binders to build buildings and underground cisterns more than 8,000 years ago. Yet it wasn’t until the early 19th century that an English bricklayer, Joseph Aspdin, patented a process where he roasted limestone and clay in an oven, then ground it into a powder in order to make ‘artificial stone’ – known as Portland cement. This process is still how virtually all modern concrete is made today.
In 2018, cement caused about 8 per cent of the world’s CO2 emissions according to think tank Chatham House. Cement is manufactured by heating ground limestone, clay and sand in a kiln to temperatures reaching 1450ºC. This results in the production of cement clinker, which is then then finely ground to produce the powder we know as cement. The fuels combusted to heat the kiln account for about 40 per cent of cement manufacturing emissions. The remaining 60 per cent are “process emissions” – i.e. when limestone is superheated, it releases its carbon atoms and forms CO2 in the kiln.
Clinker can however be blended with alternative materials to reduce emissions. There are other ways the cement industry can reduce emissions too, from improving the energy efficiency of cement plants, replacing fossil fuels with renewables and ensuring CO2 emissions are captured and stored.
The Global Cement and Concrete Association (GCCA) is an industry body that represents cement producers around the world, and is at the forefront of reducing emissions in the sector. “Last year, 40 of the leading cement and concrete companies represented by the GCCA announced a global climate ambition to drive down the carbon footprint of their operations and products to provide carbon neutral concrete by 2050,” says the GCCA’s Cement Director, Claude Loréa.
The efforts to reduce CO2 emissions span a number of areas. “During cement manufacture, [innovations] will involve new ingredients, kiln technology, new binders and reducing fossil fuel use at every stage,” Loréa says. When using concrete, we need to look at ways of better utilizing its thermal mass and recarbonation properties, and also [understand] how to unlock its recycling potential.”
“Some CO2 will need to be captured, re-used if possible, or stored using CCUS technology (carbon capture, utilisation and storage). The industry is well on its way with various trials showing the technology works and there are several live projects in North America, China and Europe. The technology works, and the industry’s next goal is to scale up, working with stakeholders such as governments and the investment community to help transform the industry worldwide.”
One company that has made changes is LaFargeHolcim, a French-Swiss multinational that bills itself as the “world’s global leader in building solutions.” According to the firm, “LafargeHolcim is the first global building materials company to sign the Business Ambition for 1.5°C pledge, setting [for] net zero. In addition, we are looking beyond 2030, to support the development of the first climate targets for a 1.5°C future in the cement sector.”
The GCCA has launched Innovandi, a cement and concrete research network, in order to “accelerate global collaboration on cement and concrete innovation.” So far 30 companies from across the concrete and cement industry as well as 40 scientific institutions, have signed up. The good news is that much of the new technology around sustainable cement already exists. “Our climate ambition is based on technologies that work today,” says Loréa. “Innovation could potentially either accelerate it or it make it easier to achieve.”
Novel cements are another option: they can lower the proportion of clinker needed in some cement mixtures. For example, LaFargeHolcim currently uses an average of 29 per cent of “constituents to replace clinker, resulting in one of the lowest levels of clinker content among international peers,” the company says.
The challenges, however, are many: major cement producers are cautious about pioneering new products; cement works well, and many users [construction companies] are unsure of the new products, while the alternative materials are not always ready at scale.
A number of organizations are working on strategies to help the ‘decarbonization of cement’ including the UN Environment Programme and the International Energy Agency. The Global Alliance for Buildings and Construction is a UNEP programme that works towards a “zero emission, efficient and resilient buildings and construction sector.” So far it has more than 150 members – including 30 countries – across the world, aiming to make progress on reducing emissions from the construction industry and making buildings more efficient. And cement firms are moving towards innovation too – LafargeHolcim is partnering with a US firm, Solidia Technologies, on development of the latter’s carbon-cured low-clinker concrete.
While industry-wide change will take time – and as concrete will continue to be used as the main building block of our towns, cities and infrastructure – it is vital that a sector producing three times the annual emissions of aviation embraces a more sustainable future.