Staffordshire University has developed and patented a new technology (known as "Stoneglass") which can convert virtually any type of waste glass into commercial quality masonry units (bricks, pavers and cladding tiles).
In particular, this process has the potential to rapidly expand a new end market opportunity for cathode ray tube (CRT) panel glass in line with the need for its more responsible recycling with the implementation of the Waste Electrical and Electronic Equipment (WEEE) Directive. Moreover, the new technology allows the use (and thereby expanded recycling opportunities) for other widely available waste glass streams that demand similar disposal attention such as automobile, fluorescent tube, plate and lamp glasses. It could also recycle considerable quantities of container glass (e.g. green and amber bottles). The Stoneglass technology allows the production of a wide range of masonry units whose features include:
- use of waste glass as its primary feedstock to give an end product with a glass content of ~97% by weight;
- a low processing energy requirement compared with traditional clay brick production due primarily to its significantly lower firing temperature;
- minimal emissions during manufacture; and
- versatility to replicate the functionality, appearance and properties of traditional clay, concrete and silica lime products.
Potential products include decorative cladding, block paving, paving slabs, cobbles, garden rocks, patio slabs, tiles and bricks. The light body colour of the waste glass feedstock means that an extensive range of through-body colours and surface patterning can be easily applied. This WRAP project was a collaboration involving Staffordshire University, a university spin-off company, a market research company and a specialist glass consultancy. Information and data for a commercial feasibility study were obtained from the production of bricks, pavers and cladding tiles using different mixes of CRT panel glass and container glass in a prototype pilot plant installed in the laboratory at Staffordshire University.
The project confirmed that the new process is ready for commercialisation and demonstrated the potential to reuse large tonnages of CRT panel glass and container glass which may otherwise go to landfill. The incorporation of Cathode Ray Tube Panel (CRTP) glass in combination with waste container glass in the Stoneglass masonry product range was shown to be non-harmful. The feasibility of mass production of the Stoneglass product range was confirmed by applying a costing model to the design of a turnkey brickworks and tile production plant. The high cost of third party supply of milled glass and concerns about security of feedstock supply prompted the drawing up of a detailed specification and costing of a front end glass processing plant.
An extensive market survey embracing building product wholesalers/retailers, the construction industry, architects and designers, local authorities and the general public produced a favourable response from all sectors. The survey highlighted the potential application of the Stoneglass product as a cladding unit in prefabricated building products and other applications. Successful market penetration will depend on being able to demonstrate value added features. A good BREEAM ecopoints assessment would help to provide differentiation. Testing by an independent UKAS accredited laboratory confirmed that the bricks, pavers and cladding tiles produced using the Stoneglass technology met relevant BS: EN Standards for existing clayware products. Environmental exposure studies have been set up on the university campus and, in collaboration with Stoke-on-Trent City Council, test panels of the Stoneglass pavers have been laid in a pedestrian walkway area.
An environmental impact assessment demonstrated that the resource requirements and carbon dioxide emissions during production are significantly lower for the Stoneglass masonry products than for traditional clay brick products. There is no need for additional precautions over traditional clay products during the handling, installation and end-of-life disposal of the Stoneglass products. These masonry units also offer the advantages of an absence of crystalline silica (classed as carcinogenic if inhaled) and the potential for closed loop recycling.