There is a very bright future for quality ash, here are four key reasons why.

#1. >100 million tonnes of reserves identified.

UKQAA members have identified more than 100 million tonnes of CDFA reserves at operating power stations or in legacy stockpiles at sites that have been closed over the past 10 to 15 years. The UK Government has recognised the vital strategic importance of these reserves, by including them in the latest version of the National Planning Policy Framework, safeguarding the future of ash deposits for future generations.

#2. Research with Dundee University.

Research is revealing the huge potential of legacy stockpiles of CDFA. The UKQAA, together with state-owned Swedish mining company LKAB and Master Builders Solutions, have been sponsoring a PhD research project at Dundee University’s Concrete Technology Unit.

The main objectives have been to understand:

The physical and chemical characteristics of long-term storage of CDFA
How legacy stockpiles can be processed to meet current European and US standards
The implications of stockpiled CDFA on concrete durability
The attributes of ternary blends of stockpiled CDFA with ground granulated blast furnace slag
Optimisation of admixtures to improve concrete and mortar properties with recovered stockpiled CDFA

#3. Commercially proven technologies.

The UKQAA’s members are at the forefront of testing and pioneering new technologies to harvest and process stocks of CDFA. Indeed, the UKQAA provides an excellent forum for companies to introduce their latest innovations.

Three of our members – Atritor, ST Equipment & Technology and Coomtech – provide compelling examples of processing technologies that are unleashing the potential of CDFA.

Atritor’s dryer and de-agglomerator, which first operated in the 1920’s, has proven to be ideal for processing stockpiled CDFA. Pilot trials have also demonstrated that the Atritor plant can be set up to optimise fineness according to requirements.

The STET tribo-electric separator was first used commercially to separate carbon from fly ash in 1995 and since then, STET separators have been used to process more than 25 million tonnes of CDFA. The pilot plant trials, partnering with Atritor in Coventry, demonstrated that legacy stockpiles of CDFA with carbon levels in excess of 15% could be processed to meet EN 450 A/N or EN450 A/S. STET Separators have successfully processed CDFA with over 20% carbon.

Coomtech’s groundbreaking cleantech offers low-emission kinetic drying technology emitting up to 75% less CO₂ than traditional drying methods. As drying energy accounts for well over 80% of the energy for processing stockpiles of CDFA, any technology or process that can reduce this figure will make a major contribution to lowering the carbon footprint.

#4. Strong sustainability credentials.

Every tonne of CDFA used to replace cement in concrete or mortars saves around 1.6 tonnes of virgin materials in the form of limestone and shale or clays. Furthermore, the physical and chemical properties of CDFA make it a unique pozzolanic material in terms of the properties it can impart to concrete and mortars.

The physical and chemical properties of CDFA also offer many advantages over sand for non-cementitious applications such as grouts and autoclaved aerated concrete blocks. Indeed, as a result of the lower density, every tonne of CDFA replaces > 1 tonne of sand.

In terms of CO₂, every tonne of processed stockpiled CDFA used in cement and concrete saves some 760kg of CO₂ and the underlying assumptions and calculations are provided in the attached link.