school energy&environment

Glass

Glass is both fragile and eternal, and it is one of the most interesting materials from the point of view of recycling. Because of its physical and mechanical characteristics it is a particularly interesting material that does not become degraded qualitatively during the recycling process and can be reutilized practically an infinite number of times. A bottle that is melted again in the furnace of a glass industry, will generate another bottle with the same qualities as the previous one, and this total recyclability enables a remarkable energy saving in the melting phase. FFurthermore, with regard to this material the percentage of recycled glass in Italy is high, equal to 70.9% of the material consumed in the market in 2015, according to the estimates made by Co.Re.Ve., the consortium in charge of glass collection and management.
The glass that is collected initially is subjected to a first selection, in order to remove any polluting materials, it is then crushed and any metal parts are removed. A final manual separation takes place in order to remove any ceramic and metal residues that may still be present. The material that is obtained is called glass cullet which is ready to be melted in the furnace. At this stage the glass production phases begin, which include mixing sand (silica) with limestone, soda and additives, plus a variable percentage of crushed glass (up to 90%). The materials are baked in special furnaces up to 1500°C, in order to reach the melting point. The vitreous mass that is obtained is sent to specific machinery where it is blown in moulds and transformed into new containers. Use of glass scrap requires a lower temperature for the material to melt than the raw materials and produces less atmospheric emissions. Furthermore out of 1 kg of glass scrap 1 kg of new product is obtained. Energy and material savings are very significant, equal to 25-30% and 100% respectively, and there is a 40% decrease in CO_2eq emissions.

Sources:
FEVE, The European Container Glass Confederation
CO.RE.VE., Consorzio Recupero Vetro (in italian)
Cassinelli N., Del Duro R. La raccolta differenziata dei rifiuti e il riciclo delle materie seconde,  FrancoAngeli, 2007 (in italian)