Minerals - The Ecology of Building Materials - page 105

Ecological aspects of glass production
The reserves of raw material for glass production are rich, even if deposits of
quartz sand are regionally limited. Accessible reserves of the metallic oxides nec-
essary for colouring or covering energy glass, most often tin and gold, are gen-
erally extremely limited. The most important environmental factors are the high
primary energy consumption with related energy pollution, and the material
pollution. Pollution by quartz dust and calcium chloride can also occur. When tin
oxide is applied as a vapour, hydrogen chloride and hydrogen fluoride are emit-
ted, in addition to tin pollution. Gold film emits less pollution than tin.
Glass does not produce pollution when in use, but both antimony trioxide and
arsenic trioxide can seep out after disposal, causing environmental pollution.
Coloured glass and metal-coated glass may contain heavy metal pigments which
can be washed out on a dump, and must be left at a controlled waste-disposal
tip.
Clear glass is very well suited for recycling. The production of new glass can
in principle use up to 50 per cent returned glass. Recycled glass can also be used
in the production of glasswool, foamglass and granulated glass (see 'Foamglass',
p. 268) Glass covered with a metal film cannot be recycled.
Production of glass has become sophisticated and technology-dependent, and
requires high investment. It is difficult to imagine that a small plant for local pro-
duction of perhaps, 1 ton in 24 hours could be competitive in both price and qual-
ity. For glass with a lower standard of translucency and clarity it should be pos-
sible to set up local production based on casting, recycled glass, etc. for products
such as glass blocks.

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