Where do we go with our polystyrene?

When I think of Polystyrene my mind conjures pictures of drinking cups, egg trays, meat trays and picnic plates. This spongy material is called Expanded Polystyrene (EPS). EPS was invented in 1952 by BASF.

It is a lightweight cellular material derived from petroleum and natural gas by-products. It is initially produced as small beads containing a blowing agent. The beads expand when treated with steam, forming a lightweight prefoam of the required density. There are 7 types of plastic on our market and polystyrene is called number 6.

As it’s filled with 95% air it turns out lightweight with excellent insulation properties – ideal for that delicious take-away cappuccino. The fast food industry relies heavily on EPS, as it’s been proven more sanitary than reusable plastics. EPS can be washed in the dishwasher or by hand and used again. Insulation for the home, called Isolite, is also made of EPS. Then you also get High Impact Polystyrene (HIPS) which is not that easy to identify. High Impact Polystyrene (HIPS) is rubber modified impact polystyrene with Izod impact values between 1.5 and 2.5 ft-lb/in.

Izod impact measures the amount of energy a notched injection molded specimen absorbs while being struck with an instrumented hammer. You might see the number 6 underneath, but if not, just bear in mind that most yoghurt cups and most clear, soft containers are made of HIP, such as clear salad containers. (Not the PET clear plastic, which most cooldrink and water bottles are made of – this is harder.) So too plastic cutlery and cottage cheese containers.

Eco benefits

Polystyrene has eco benefits too: its lightweight quality lowers the carbon footprint when packaging is transported. No CFCs (chlorofluorocarbons) are used in the manufacturing process, which protects the ozone layer. It also uses less energy in manufacture and recycling than paper and glass and is more economical than paper board and reusable food service items. Gone are the days when we used to feel bad to use polystyrene packaging, as it is can now be recycled in a number of ways.

Pure EPS scrap can be ground down and used for the production of new EPS, mixed with soil as a composting aid or used as a lightweight aggregate for concrete and insulating mortars. Waste EPS can be applied in feedstock recycling, where it is used as a chemical source in the production of other materials, such as crude carbon for the manufacturing of steel. Colin Feder from EPS Reclaim in Montague Gardens (pictured on this page) kindly showed me how they contribute towards the recycling of polystyrene. Their company collects about 10 tons of used polystyrene from businesses, schools, malls and materials recovery centres per month.

First the different colours are separated, then a hammermill pounds it down into granules that are sucked up into canvass bags mounted on top of 4 elements with steel screws inside. When full it is heated up to 200 degrees Celsius, so it melts inside. This is called extrusion. This liquid pours out in long tubes into ingots or moulds of 10kg each. The ingots are transported to the Supreme Mouldings factory in East London. Here they are pelletised again, melted with added colours and moulded into new products – made from non food bearing HIP.

They make curtain rods and holders, skirtings, picture or mirror frames, clothes hangers, seedling trays, cellphone shells, computer outer casings, CD boxes and make-up containers.