SA Affordable Housing March - April 2019 // Issue: 75 - Page 14

FEATURES Portland cement was used in the construction of the Burj Khalifa, which at 829.8m is the world’s tallest building. cubic metre of concrete. In 2010, China produced almost 1 868 million metric tons of cement, representing a whopping 10% of the nation’s total coal consumption. Cement production has increased more than thirtyfold since 1950 and almost fourfold since 1990 alone. On his blog Bill Gates explains that between 2011 and 2013, China consumed 6.6 gigatons of concrete – that's more than the 4.5 gigatons that the US has used in the entire 20th century. In 2016 alone, world cement production generated around 2.2 billion tonnes of CO 2 , which is equivalent to 8% of the global total. More than half of that came from the calcination process. Together with thermal combustion, 90% of the sector's emissions could be attributed to the production of clinker. China is far and away the leading producer of cement and according to a report by the Energy Analysis and Environmental Impacts Division at the Lawrence Berkeley National Laboratory 1.6 million Chinese citizens die each year from respiratory illnesses linked to small particulate matter emissions, of which 27% of deaths are related to cement production. Excavating sand – a critical input for cement – adds to the environmental costs. ‘Most of the nearly 50 billion tons of sand and gravel mined or dredged every year is used to make concrete,’ according to Vince Beiser in his book, The World in a Grain: The Story of Sand and How it Transformed Civilization – that’s more than enough to blanket the entire country of France. It’s an inconvenient truth and one that the industry is trying desperately to overcome. But the sector has made progress, improvements in the energy-efficiency of new plants and burning waste materials instead of fossil fuels has seen the average CO 2 emissions per tonne of output fall 12 MARCH - APRIL 2019 "Cement is a natural ingredient that, in terms of strength, is far and away better than any of its competitors." by 18% over the past few decades, according to The Royal Institute of International Affairs based in London (more commonly known as Chatham House). It’s a difficult task, however, says general manager for the Concrete Manufacturers Association Henry Cockroft. “Cement is a natural ingredient that, in terms of strength, is far and away better than any of its competitors. For years the industry has looked into finding sustainable alternatives such as fly ash or coal slag, but they just don’t deliver the options, and value that cement does,” Cockroft explains. According to Cockroft, the areas in which cement can be increasingly less environmentally hazardous are all being investigated. “The areas we can change, and are already making inroads into, include how the product is transported; the logistics around getting the product from quarry to building site, using alternative fuels for the calcination process, that sort of thing,” says Cockroft who believes that while alternatives may eventually be developed, it will take a long time before engineers, architects and builders trust them as much as they trust concrete, and start to specify them for construction. In her Mechanical Engineering dissertation at the Potchefstroom campus of the North-West University titled Demand Side Management opportunities for a typical South African cement plant, Raine Tamsin Lidbetter explains how choosing different types of machinery at each level of www.saaffordablehousing.co.za