WRAP has defended its work to encourage the use of recycled glass in making aggregates or cement, in the light of a report suggesting that environmentally it isn't the best use of resources.

The report, to be published in the Resources Conservation & Recycling academic journal, examines the environmental outcomes of various uses for recycled glass.

John Butler and Paul Hooper of Manchester Metropolitan University said that there are some environmental benefits to using recycled glass instead of virgin aggregates.

But, they said these benefits are "significantly less than those accruing from the substitution of cullet for virgin raw materials in the production of glass containers".

Beneficial

As a result, the report argues that transporting household and commercial arisings of waste glass (cullet) for use in glass container manufacturing in EU countries "provides a significantly more beneficial environmental outcome than its use as secondary feedstock for base aggregate and other building materials within the UK".

Recycled glass cannot all be recycled into glass containers within the UK because a surplus of green glass arises in the waste stream compared to the demand from the domestic container industry.

The research states energy savings of about 70MJ per tonne if the recycled glass replaces virgin material in making aggregates. However, if the glass was shipped to France – where there is more demand for green glass to be made into bottles – energy savings would be about 4000 MJ per tonne, it said.

WRAP

The Waste and Resources Action Programme has funded some major studies into making concrete and aggregates from recycled glass, and is currently carrying out trials. The government-funded market development organisation is aiming to increase glass recycling by an annual 150,000 tonnes through the development of markets outside the container industry.

Commenting on the findings of the report, WRAP director of materials programmes Dr Liz Goodwin said the organisation had always recognized the importance of recycling glass containers back into container manufacturing.

She said: "There are clear environmental benefits from closed loop recycling into the container sector and it is clearly a more valuable end market than use in applications such as aggregates."

Sustainability

However, Dr Goodwin highlighted concerns with the long-term sustainability of exporting glass to container manufacturers abroad – particularly since other European countries are pushing to meet glass recycling targets of their own.

Dr Goodwin said: "Future growth in collection by other countries may well mean that the container sector is able to meet more or all of its requirements from other sources and hence they may not wish to import glass from the UK in the longer term.

"This is one of the reasons why WRAP has been working on the development of a range of end applications that can utilise recycled glass and provide a number of sustainable outlets," she explained.