16 November 2019 | New Scientist | 41arch-based design would have required.
Similar approaches are being explored for
concrete. “Our mantra is use enough material
and no more,” says architectural researcher
Paul Shepherd at the University of Bath, UK.
In January, he started construction of an office
building using concrete beams that can bear
the loads needed but are shaped to require
less material than usual. And in some cases,
we could just use wood instead.
Back at the steelworks in Newport,
management are understandably hoping to
ramp up the amount of metal they turn out.
If things go to plan, output could double next
year. And yet globally, the most credible and
readily available route to a low-carbon future
lies in the opposite direction. That is certainly
how Kirsten Henson at KLH Sustainability,
a construction consultancy that advised the
London Olympics, thinks about steel and
concrete: “We’ve got to use less of it,” she says. ❚In principle, carbon capture and storage
technology could help mitigate the carbon
footprint of both concrete and steel. It is often
mooted as a potential solution in the energy
sector, and Luke Warren of the UK Carbon
Capture and Storage Association says attention
is beginning to turn to its use in heavy industry.
However, the truth is that the technology
is still in its infancy. Despite its undoubted
promise and years of efforts to make good on
it, there are only 23 large-scale facilities in the
world, capturing 40 million tonnes of CO 2 a year,
chiefly in natural gas processing plants where
it is easier to implement. That amounts to just
0.1 per cent of humanity’s emissions.
Ultimately, the quickest climate win for both
concrete and steel may end up being the
simplest: use less of it, and make what we do use
last longer. In the book Sustainable Materials:
With both eyes open, Allwood and his colleagues
sketch out how we could cut the emissions from
these two materials by 50 per cent by 2050 by
designing buildings to use less of them. A case in
point is the velodrome built for the 2012
Olympic Games in London, for which the choice
of a lightweight roof made of steel cables meant
using 27 per cent less steel than a conventionalAdam Vaughan is chief
reporter at New ScientistSome carbon savings are already made
by using existing cement substitutes.
One is fly ash, a fine powder produced as
a by-product by coal power stations. Another
is a by-product of iron-making called ground
granulated blast-furnace slag. But we are
trying to phase out coal plants for good
reasons, and there is only so much of this slag.
Elsewhere, researchers have started
looking at using a calcium silicate slag that
is a by-product of the steel industry as a
substitute for cement. It is typically dumped
in landfills. Carbicrete of Canada is one firm
eyeing this route and promises great carbon
savings, but it is unclear, commercially
speaking, if it has made any inroads.
All of these new formulations share two
main problems. The first is a familiar one: they
are more expensive than the current recipes.
The second is a consequence of the first. No
one is making them in volumes that would
start to bring costs down. “There are
alternative cements being developed in labs,
but none at meaningful scale,” says Allwood.
A glimmer of hope can be found in Lixhe,
Belgium, where researchers are experimenting
with a different approach. Here, a plant owned
by German company HeidelbergCement
has been retrofitted with a 13-storey tower
designed to capture the carbon produced
during cement-making before it gets into the
atmosphere. The aim of the Low Emissions
Intensity Lime And Cement (LEILAC) project,
partly funded by the European Commission,
is to test a new technology – one that separates
the CO 2 released from other waste gases, to
capture a pure stream of CO 2.
Capture and convert
Fennell, who is involved in the project,
believes it has promise in part because the
CO 2 could be a commodity to sell to other
industries, such as plastic manufacturing.
“It’s one of these rare processes that might
have very little downside,” he says.
Scaling up could have an eye-watering
price tag, though: LEILAC is a €21 million
scheme, but will handle just 2 per cent of
production at Lixhe, a typical-size cement
plant. That hasn’t stopped HeidelbergCement
pushing ahead with a report, based on a
similar trial at a Norwegian cement plant,
that will have a big say on whether it sinks
funds into a full-scale project in Norway.
Pouring concrete at
a building development
in Montreal, Canada
“ The quickest climate win
for concrete and steel
might be the simplest:
use less of it”
ARAMHOVS
EP
IAN/^ WWW.ARTO
FC
ONST
RUCT
ION.PHOTOGRAPH
Y