The recycling of EPS

Expanded polystyrene recycling is a challenge unto itself, and relatively few recyclers, even of other plastics materials, are willing to take on EPS. Special equipment and technology setups are required to deal with this unusual material. Even conventional equipment, such as conveyors, granulators and extruders, must be adapted to the specific characteristics of EPS.

For one thing, EPS is variously described as 95 to 98 percent air, by volume. Dart Container Corp., Mason, Mich., an assertive proponent of recycling EPS, reports that a standard 48-foot-long semi trailer could hold about 1,000 pounds, a mere half a ton, of EPS before it is compacted or, as it is known in the business, densified. At a compression ratio of approximately 40-1, the same vehicle can hold about 40,000 pounds (20 tons) of the material. 

The initial problems with recycling EPS are not technical as such, but are in the realm of politics and economics. It is not easy to convince municipalities or other waste-collection entities that it is worthwhile to collect EPS, especially in a single stream, or even in mixed waste. The stuff is bulky, takes up a lot of space in collection containers, and is prone to flying away and creating debris during handling. Recycling EPS is not for the faint of heart. You’ve got to want to do it.

After used EPS material is gathered, by whatever means, the next problem, since not much of it comes in pre-sorted, is to sort it out of the stream of mixed waste. The initial step can be done by the patently low-tech means of having it taken off a moving conveyor by workers, who pull EPS off the stream as the conveyor moves along. Don’t laugh. The first step of some EPS reprocessing is done exactly this way. The work is well-lit, and requires no heavy lifting.

After that, things get a bit more complicated. The EPS scrap is thrown directly or moves by conveyor into a granulator, which need not be burning up energy and making noise by being on full time. A sensor on the hopper can determine when the hopper is full and trigger the granulator’s operation, which, with the appropriate rotor, blades, and rotor speed, can literally grind the EPS waste to bits.