Cullet—or recycled waste glass—can often be a technical substitute for the mix of virgin raw materials (‘the batch’) used in making glass, and is therefore able to replace silica/glass sand up to certain limits.
Benefits of Recycling Glass -Cullet
Cullet use may result in both private and public benefits or cost savings.
- By reducing batch melting temperatures, each 10 per cent increase in cullet use allows savings of around 2.5 per cent of the total energy used in glass furnaces. Alternatively, when cullet is added to the batch, the furnace load increases by some 10 to 15 per cent. The benefits are therefore either an increase in furnace efficiency or an increase in overall production capacity.
- Public benefits come in the form of reduced carbon dioxide emissions, brought about by:
(a) a reduction in fuel consumption; and
(b) reduced usage of soda ash, limestone and dolomite, which are all carbonates giving off carbon dioxide when melted. Recycling also reduces the amount of solid waste going to landfill, and generally reduces the use of natural resources, including sand.
Each tonne of cullet used, for example, saves around 1.2 tonnes of raw materials in the batch. Assuming that silica/glass sand accounts for 60 per cent of the batch raw material, each tonne of cullet replaces around 0.72 tonnes of such sand.
Public policy and legislation, including the UK Waste Strategy and Packaging Waste Regulations,
aim to increase recycling rates, which for glass is currently just over 30 per cent in Great Britain. Across Continental Europe, several countries report glass recycling rates of 60 to 80 per cent; and the European Commission is understood to be considering proposals for a 75 per cent target for all member states.
Reference: All figures quoted from the Competition Commission.