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
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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
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