Tetra Pak is to pilot the use of renewable polyethylene as a raw material in the manufacture of its plastic caps and closures within the next two years.

The carton manufacturer has signed an agreement with Brazilian company Braskem, a thermoplastic resin producer, to buy limited volumes of high-density polyethylene (HDPE) from a renewable feedstock.

Braskem plans to open the world's first commercial-scale 'green' polyethylene plant in late 2010 and aims to deliver its first batches to Tetra Pak in early 2011.

Under the terms of the contract, Braskem will supply Tetra Pak with five kilotonnes of green HDPE per year, which will represent 5% of the company's HDPE demand and slightly less than 1% if its total plastic purchases.

"While this pilot project is a small first step into green polyethylene, it marks another milestone in our sustainability journey and underscores our commitment to finding new ways to use renewable materials in our carton packaging," said Dennis Jönsson. Tetra Pak's president and chief executive.

The Braskem facility will use ethanol extracted from sugar cane to produce ethylene, which will then be converted into polyethylene.

Today's (25 November) announcement marks the latest move by Tetra Pak to invest in 'green' raw materials. Last month it announced that 75% of its cartons in the UK and Ireland would carry the FSC (Forestry Stewardship Council) logo and be manufactured using FSC-certified paperboard.

A Tetra Pak carton is typically made from 75% paperboard, and between 10% and 25% low density polyethylene (LDPE), which is used to laminate the inside and outside of carton. The HDPE is used to make the caps and closures. Long-life and aseptic cartons also contain a thin layer of aluminium, typically around 5%.

Tetra Pak's are collected from waste streams in the UK via kerbside collections and bring-banks. The latter system was set up by Tetra Pak, SIG Combibloc and Elopak under Ace (Alliance for Beverage Cartons and the Environment) and sees recovered cartons shipped to Sweden, where the paperboard it recovered and used to manufacture plasterboard, among other products.

The plastic and aluminium is currently not recovered, but combusted and used to power the paper mills. However, Tetra Pak and partners are trialling a method in Brazil whereby the plastic is burned as fuel gas and the aluminium is recoverable.