PET must use up more energy than glass if it is made from oil so why should it be used as an alternative?

Simply comparing manufacture of a glass and a PET bottle is misleading, it is necessary to compare what they are being used for, both are used to deliver drinks or liquids to the consumer and when compared on resources used to deliver one litre of beverage the situation is rather different. In this respect comparative studies show the PET bottle competes very well indeed, especially in the larger sizes and over longer transport distances.The environmental impact analysis over the full life cycle of the various packaging alternatives (LCA) shows that in most uses PET has very favourable results compared to the other options.