Polypropylene is a versatile polymer made up of a long chain of propylene (propene) molecules joined end to end under the action of a catalyst. It can be produced as a solid, for items such as food containers, and as a fibre for carpets and ropes.

To maintain product quality and reaction efficiency any unreacted compounds need to be constantly removed from the reaction mixture. This "bleed stream" was burnt in a converted gas-fired boiler or at the sites flare stack.

In 2001, as part of its commitment to environmental protection, Basell's Carrington site installed a new distillation unit that recovers 3,100 tonnes of propylene a year. This is recycled into the production of polypropylene which saves on the cost of raw materials as well as reducing the amount of waste gases burnt.

This investment has lead to a noticeable reduction of the flare stack flame at Carrington as well as a major reduction in carbon dioxide emissions to the atmosphere.