A range of uses for recycled glass were examined for the Life Cycle report, which was commissioned by the British Glass Manufacturers' Confederation. These included container manufacture in the UK and abroad, shot blast abrasive, water filtration, fluxing agent in brick manufacture, fibre glass and aggregates.
Enviros found that even when cullet is exported to European glass manufacturers, container re-melt achieved the greatest carbon dioxide (CO2) savings of any glass recycling operation.
One tonne of glass recycled into new containers in the UK saves 315kg CO2, or 'greenhouse gas'. If it is transported by sea to other European countries, container re-melt saves 291kg CO2. The next highest saving came from the use of used cullet to make fibreglass. This saves 276kg per tonne of glass.
Andrew Hartley, director of strategy and communications for packaging at British Glass, said: "The study takes into account all the raw material extraction, processing and transport energy used. Closed-loop manufacture is clearly the best use for recycled glass."
The UK is committed to reducing CO2 emissions by 12.5% by 2010 and 60% by 2060.Overall, UK glass recycling saves about 200,000 tonnes of CO2 each year and most of this is from container manufacturing.
But other uses for recycled glass were less effective at reducing greenhouse emissions.
The report found that "from a global warming perspective there is no environmental benefit to using recycled glass to replace quarried aggregates," British Glass said. "In fact, taking into account the increased transport and additional processing, in most circumstances using recycled glass results in a small increase in CO2 emissions."
And using glass as a fluxing agent in bricks saves just 72kg per tonne of glass, and using cullet as a shot blasting abrasive saves 19kg. Using crushed glass to replace sand in water filtration gives a net increase in CO2 when transport and processing requirements are taken into consideration.
But British Glass insisted these alternative recycling options had an important role to play in complementing container recycling and helping the UK meet its glass recycling targets.
Mr Hartley said: "Whilst the report shows that alternative uses deliver lower levels of reduction in CO2, the glass industry believes strongly that all alternative markets will be important to meeting higher targets and provide a better environmental use than landfill."
The organisation also pointed out that using glass for water filtration could improve the technology and bring health benefits and energy reduction in water pumps. The results of a WRAP report on the environmental, energy and health benefits of recycling glass for filtration are expected in April 2004.