Historically, the construction industry has relied on fly ash as a major component. But is it threatened by the closing of some coal-fired power stations? Robert Carroll thinks not
Specifiers, contractors, and construction managers are all experiencing an uptick in business, which is good news for everyone involved in the building industry. As a result, at the grassroots of the sector, demand for resources is ramping up and order books are beginning to fill.
According to a recent Mineral Product Association (MPA) study, sales of minerals and aggregates in particular are on the upswing. Aggregate sales climbed by 6% in 2013 while concrete sales increased by 11%. As the organisation I work for, the UK Quality Ash Association, representing firms who manufacture and use fly ash as a secondary resource, I applaud this news.
Coal-fired power plants produce significant amounts of fly ash as a byproduct of the combustion process, and the United Kingdom is no exception. Thus, it is a readily available, low-carbon secondary resource that may be found in many places. Concrete, bricks, and blocks can all benefit from the fine consistency and wide range of applications for which fly ash can be utilised in the UK. It is well known as a vital ingredient in modern sustainable construction, helping to satisfy environmental standards and minimise the embodied carbon of our building stock.
In recent years, however, some in the industry have become concerned about the impact that the closing of coal-fired power stations will have on the supply of fly ash – not least the harmful effect that the consequent demand to use more primary aggregates will have on the environment. The UKQAA, on the other hand, is unconcerned about these issues.
As long as coal continues to supply more than a third of the UK’s energy needs, it will be an important part of the energy mix for many more generations to come. As a result the UK already has huge stocks of fly ash – up to 50m tonnes in long-term storage – which are added to every day. Using only these existing supplies, it is possible to meet demand for the foreseeable future without adding any new manufacturing capacity.
And although EU pollution restrictions may make it harder for some of the older coal-fired power stations to continue functioning, substantial investment is planned for innovative carbon saving technology like carbon capture and storage (CCS) (CCS). The White Rose Project at Drax, for example, would allow for the continuation of more traditional methods of energy production. They will be substantially cleaner and more efficient, and therefore will deliver high grade fly ash as a result.
Co-combustion (co-firing of coal and biomass) is introduced in the UK during the interim period. Cheaper than CCS technology, co-combustion cuts carbon emissions from power stations by reducing the amount of coal consumed. The European standard for fly ash in concrete, EN 450, allows for controlled co-combustion of coal and biomass. The fly ash produced retains the same benefits as “pure coal ash” and is approved for a wide number of uses, including as a cementitious material within concrete.
All of this is reassuring news. It illustrates that despite the shifting landscape of energy generation in the UK, coal-fired power plants will still have an essential role to play for many years to come, and fly ash will continue to be a valuable low-carbon construction material. Fly ash will play an increasingly essential role in sustainable construction in the UK as new technologies are developed and implemented. As such, fly ash will continue to play an important role in the building industry as a valued component of the recovering minerals and aggregates market, whether it is used in concrete or grout.
Robert Carroll, Ph.D., serves as the UK Quality Ash Association’s technical director (UKQAA). For additional information, see its website.