CPD Specifier May 2015 issue January 2014 | Page 38

Civils & Soft Landscaping

Flying the
flag for
ash
Fly ash and furnace bottom ash (FBA) from coalfired power stations are sustainable, effective and
widely used constituents in construction products.
However, with coal-fired power plants closing
down, what does the future hold? Dr Robert
Carroll from the UK Quality Ash Association
(UKQAA) says it’s not all doom and gloom, and
there’s still plenty of fly ash available to the
industry.
Coal is cheap, plentiful and in 2012 provided around 40 per cent of the UK’s energy needs, meeting
essential demand even as we explore alternative sources of energy. As complex arguments about
fuel prices, energy security, carbon reductions and investment choices are debated in the political and
public domains, it is likely that electricity generation from coal will remain central to the economy for
some time.
Closure of some coal-fired power stations across the UK is likely as a consequence of EU pollution
legislation and the need to reduce carbon dioxide emissions. Operators of coal-fired stations face big
financial decisions regarding investment in plant and the construction industry will be watching closely especially those companies that use fly ash and FBA.
Today, fly ash and FBA are widely used throughout the construction industry in a range of end products
and applications. From the concrete in office buildings to embankments on major roads, and from the
engineering feats of the Channel Tunnel to the glittering Shard, coal ashes feature in all manner of
construction projects.
The use of these by-products supports the sector’s continued move towards
greener building. Using secondary resources is more sustainable than reliance
on quarried primary raw materials. As by-products of the combustion process,
selection or processing to obtain desired properties may be achieved cost
effectively and with modest energy input. In concrete or blended cement the
incorporation of fly ash produced to EN 450 standard significantly reduces the
embodied carbon dioxide of a finished product with no reduction in structural
strength or quality.
So what does the future hold for fly ash and FBA in the UK?
In the short term, there will be relatively little change for the sector. Coal-fired
power stations produce fly ash and FBA at significant rates throughout the
year, and although seasonal fluctuations (warmer winters, cool summers)
have an impact on energy consumption, more than 50m tonnes of fly ash and
FBA sits in storage sites across the UK and with processing would satisfy
demand for several years even if all the coal-fired power stations close
tomorrow.
Over the long term although the picture is less certain, it’s not entirely
negative. While existing coal-fired power stations will close as legislation
dictates, coal remains a cheap and accessible source of fuel and attractive
to investors. Innovative ‘clean coal’ technologies , such as the ‘White Rose’
Carbon Capture and Storage (CCS) scheme, offer the prospect of significant
reductions in carbon emissions, perhaps justifying the substantial capital
investments required.
Co-combustion (the co-firing of coal and biomass) also has a role to play
and is increasingly being implemented as a way to reduce carbon dioxide
emissions at coal-fired power stations. Fly ash produced from controlled cocombustion is permitted in EN 450, allowing it to be used as a cementitious
material within concrete.
This is all encouraging news. As coal-fired power generation must change, but
what’s not inevitable is a complete loss of important construction resources.
As technologies improve, the production of fly ash and FBA will remain in
place for many years to come, and will feature heavily in the future of the
construction industry - whether it’s in the next major engineering product or the
next big skyscraper.

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www.ukqaa.org.uk

01902 37