Environment
Environmental Benefits of ScotAsh Products
ScotAsh is a business founded on the principles of sustainability. We take the ash from ScottishPower's coal-fired power stations and re-engineer it into quality construction products.
Recycling PFA in construction products has major environmental benefits.
Conserving Natural Resources
PFA-based products displace primary aggregates, helping to conserve valuable natural resources. Due to its low density, re-using ash in this way saves a greater weight of natural aggregates and reduces transportation impacts and costs. During the last three years Scotash has saved more than one million tonnes of primary aggregates.
Saving Energy and Carbon Dioxide
The re-use of ash also saves energy (and CO2 emissions) that is required to crush, grind and heat raw materials. The manufacture of traditional Portland cement, widely used in construction, is one of the most energy intensive production processes - only materials such as aluminium and steel require more.
Making one tonne of Portland cement requires about 4Gj of energy. This makes the process a significant contributor of the greenhouse gas CO2. Each tonne of Portland cement results in emissions of 0.89 to 1.1 tonnes of CO2 depending on the type of process used.
About half of the CO2 emissions are due to the calcination of limestone, with the remainder due to the combustion of fossil fuels in energy production. Each tonne of PFA re-used in cementitious products saves around one tonne of CO2 emissions. During the last three years ScotAsh's use of PFA in cementitious products has saved 100,000 tonnes of CO2 - equivalent to taking 32,000 cars off the road for a year. In addition, using processed PFA as an addition to concrete lowers the water demand, which in turn saves energy.
Reducing Landfill
Processing a by-product into quality products avoids the need to landfill substantial quantities of ash, either to ash lagoons or conventional landfill sites.
During the last three years ScotAsh has avoided the need to landfill around 1.3 million tonnes of ash.
Waste Stabilisation
Powder technologists at ScotAsh have harnessed the unique characteristics of Pulverised Fuel Ash (PFA) to produce cementitious binders for in-situ remediation of contaminated land, excavation spoil and sludges.
PFA has a glassy structure, with spherical particles - the result of pulverised coal being burned at extremely high temperatures - that can immobilise contaminants within a solid matrix.
Environmental binders from ScotAsh provide a sustainable alternative to the conventional "dig and dump" approach to remediation.
Remediation of excavated materials generally means they can be re-used as fill, avoiding the need to landfill. Where remediation is conducted in-situ, this significantly reduces vehicle movements and the transportation costs of removing arisings from site and bringing in new materials.
It also reduces the environmental and safety impacts of using heavy vehicles, including lower emissions of CO2 and NOx, reduced fuel usage, a reduction in traffic congestion and enhanced road safety
Recycled Roads
ScotAsh products have been used by geotechnical experts to develop sustainable solutions for road maintenance.
At Finsbury Park in London, a damaged road was excavated and the arisings were milled in-situ and blended with RSA/PT, a pozzolanic and hydraulic material, custom blended by ScotAsh. Following the addition of water and rotovation, the mixture was compacted back down, providing a new surface using 100% recycled materials.
A similar project was conducted at Rainham landfill site in Essex using, in addition, milled waste aggregates from taken from landfill.
In Edinburgh, ScotAsh products were used to repair a badly deformed setted roadway at Whale Brae. The project involved stabilising the clay-contaminated sub-base, laying a thin base of asphalt and re-constructing a stretch of roadway using the original whin setts and the Sika Trojan Paving System of complementary bedding mortar and joint filling grout.
The Sika Trojan Paving System was used in a £1.5 million refurbsihment of a 300-metre section of Edinburgh's historic Royal mile during 2006/07.
High carbon PFA from ScotAsh can be used in various black-top applications, including as a limestone dust replacement in Stone Mastic Asphalt and as a component of Durafoam, a foamed bitumen Macadam, manufactured by Linear Quarry Products using 95% recycled materials.
For further information on the projects mentioned here, visit our Case Study library in the News & Information section.
Downloads:
ScotAsh Environmental Policy (pdf)
ScotAsh CR Report 2006 (pdf)
ScotAsh and the Environment leaflet (pdf)
Sustainable Construction Products for Renewable Energy projects (pdf)
Longannet Power Station EMAS Statement 2006 (pdf)
Lafarge UK EMAS Statement 2006 (pdf)
