One of the most common and rising sources on the planet is hardly mentioned by most campaigners. It is not oil, or coal, or shipping – or even farty cows. Cement is used in every country in the world, and it is a massive contributor to CO2 emissions. By James Teo.
Singapore, 29 January, 2019. Concrete is the second-biggest resource consumed by humans worldwide. It only comes a close second to water. Even more worryingly, it contributes a massive 8% of all the CO2 released into the atmosphere. That was some 2.2 billion tonnes of CO2 in 2016, and the figure is rising every year. Unbelievably, if the cement (the key raw material in concrete) business was a country, it would rank just behind the US and China as the biggest culprit. After fossil fuels and land-use change, concrete is the third-largest source of anthropogenic emissions of CO2.
Research institute Chatham House, in a recent report, noted that “… each year, more than 4 billion tonnes of cement are produced, accounting for around 8% of (total) global CO2 emissions.” In comparison, aviation produces just 2.5%, and the whole of the worldwide agricultural sector 12%.
To compound the problem, cement production is slated to increase as demand for more buildings, bridges, and infrastructure ramps up. Global cement production is predicted to increase from 4 to over 5 billion tonnes by 2050 as governments and builders invest in huge new infrastructure projects.
Unfortunately, seriously large emissions are directly attributable to the production of cement process; it needs lots of heat and power to make the clinker – the key ingredient. But to bring “… the cement sector in line with the Paris Agreement on climate change, its annual emissions will need to fall by at least 16 per cent by 2030,” says Chatham House. This is an equation that cannot be solved using current materials.
The first use of concrete is dated back some 8,000 years, used by builders in Jordan and Syria to line underground cisterns. And the largest free-standing concrete dome in the world was built by the Romans in 115AD, on top of the magnificent Pantheon in Rome. Modern concrete used much the same materials, but now uses very high temperature ovens to char limestone and clay in a furnace before it is ground up to make the familiar powder we see being mixed and poured on hundreds of building sites every day.
The raw materials, limestone and clay, are quarried and crushed producing lots of airborne dust and debris. This is then mixed with equally nasty stuff such as waste power station ash and other fillers. The whole mix is then poured into massive rotating kilns that are heated to almost 1,500 deg C.
Not only does this demand huge amounts of energy as millions of tons of what is effectively rock have to be heated, but the result is that the mix gives off large amounts of extra CO2 as it chars. It’s a double-whammy of greenhouse gas that – at present is hard to avoid if we carry on using concrete. The result of all this heating and mixing is cement clinker, which is then mixed with gypsum to make the final product.
As a result, many research labs and companies are working on the production of concrete materials that cut down the emissions that our favourite building material produces.
Some companies are working on ways to capture the excess CO2 emissions by using scrubbing technology that filters out the unwanted gas and freezes it for use in other processes, or to send for storage underground.
Columbia University research has revealed that simply tightening up existing processes could make a lot of difference. It says that the use of alternative fuels, including natural gas, biomass and recycled wastes like rubber, sewage and burnable garbage. “These less carbon-intensive fuels could reduce overall cement emissions by 18-24% … by 2050,” says its research team.
Another approach is to take some of the excess CO2 and inject it into the concrete as it is being poured. Rob Niven, CEO of Canadian company CarbonCure Technologies says that because the concrete is injected with surplus carbon dioxide, the resulting secondary chemical reaction produces a stronger, faster-setting kind of cement with the bonus of a lower carbon footprint up to 10 -15% less than normal.
"We've finally cracked the code and are now in the ready-mix market," said Niven in an interview. "It’s what we have been working towards for five, six years.”
And other companies are working on trying to duplicate the world of corals, and pulling materials from the biological and atmospheric worlds to produce bio-bricks – but nobody has yet come up with a better alternative to poured concrete.
The concrete industry is also taking note. Carbon- and limestone free alternatives that use blast furnace slag and other waste products are being trialled as alternatives – but only for precast materials. The industry has ramped up its efforts to improve its record too.
The Global Cement and Concrete Association (GCCA) CEO Benjamin Sporton says that “… sustainability, innovation, and … tackling climate change will be at the heart of everything we do.” That’s good to hear, but if the world continues on its current concrete-led development splurge, that will be hard to maintain.
“If the IPCC report (on global warming, from late 2018) represented a global fire alarm, this report is the arson investigation,” said UNEP’s Deputy Executive Director Joyce Msuya. “Governments need to move faster and with greater urgency. We’re feeding this fire while the means to extinguish it are within reach.”