The combination of increasing production and falling cullet use has led to a fall in the recycled content of UK-produced glass containers, from 36 per cent in 2005 to around 30 per cent in 2007 (Graph 2). The most significant decline has been in green furnaces, which are currently operating with a cullet content of less than 70 per cent, compared with around 85 per cent in 2005. This is significantly lower than the technical limit, which suggests that the so-called ‘green glass mountain’ may have disappeared, a stark contrast to the story of recent years.
In addition, it is estimated that around 80,000 tonnes of flat glass was used in domestic container glass furnaces in 2007. Industry contacts have indicated that they are using more flat cullet, in part owing to shortages of clear container cullet, although there are technical limitations due to differing glass chemistries. Exports of cullet for overseas container manufacture rose by over 40,000 tonnes in the year to June 2008. Although this increase – against a background of declining UK usage – seems surprising, it reflects two key factors.