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Questions & Answers on EPS Recycling Technology

Q: What is EPS?

A: Expanded Polystyrene (EPS) is made from PS resin granules impregnated with a blowing agent (typically pentane). Expanding beads fuse together to form the finished product, which is white, and 95 to 98 percent air and another 2 to 5% is polystyrene which is pure hydrocarbon. Small beads are used for cups and containers, medium beads for shape-molded packaging, and large beads for the expanded loose-fill packaging (peanuts). It insulates, is lightweight, and resists moisture.

Q: How to produce EPS?

A: Expanded Polystyrene (EPS) is PS foam that use pentane gas as the blowing agent. During the material production process call “Polymerization” the polystyrene resin granules impregnated with the blowing agent. EPS production process begins in the pre-expansion process where the EPS bead will expand by the heat of steam usually 50 times in volume. Next step is molding process where expanded foam bead will be heated again with steam then they expand further until they fuse together, forming as foam products.

Q: How to manage the EPS foam waste?

A: Waste EPS is generally from construction, packaging and container. It is expensive and difficult to transport due to its volume to weight ratio.
The main methods to treatment used EPS are as follows.

  • Landfill: unable to biodegrade;
  • Burning: generating heat;
  • Compacting and pelletizing: using EPS recycling and pelletizing machines turning waste EPS into PS pellets and manufacturing various products such as coat hanger, flowerpot, video cassettes, etc.
  • Melting and pelletizing:
  • Reground and mix with concrete to produce new building products such as prefabricated concrete blocks to reduce the weight and increase insulation properties;
  • Crush into small particle and mix with soil to improve ventilation in the soil.

Q: How to recycle used EPS?

A: Since EPS foam is made of Polystyrene, which is thermoplastic, so that it will become again a polystyrene plastic when recycled. There are two main options for recycling EPS waste: incineration – yielding energy-recovery, and recycling into other forms such as garden furniture and building insulation. Both require the EPS to be compacted first.
How to Recycling EPS Styrofoam

Q: How to densify EPS?

A: Densification can be carried out with heat (thermal densification), or without heat (cold compaction).
Cold compaction involves crushing and compacting EPS by machine. The compacted materials are extruded into a solid ‘log’. The log is cut to length to fit onto a pellet. It is usual for the compacted EPS to be stored on-site until 5 to 20 metric tones are available, as this makes transport and distribution more cost-effective. The more densely compacted the EPS is, the better, since a higher weight of EPS can be loaded for transport and a higher price per tone may be paid by the recycler. Cold compaction can reduce EPS volume down to one-fortieth of the original.
Thermal densification involves breaking up and melting EPS inside a controlled-temperature chamber. The temperature is controlled to allow the EPS to melt without burning. This collapses the expanded foam cells, enabling it then to be recycled into other products. Higher compaction ratios (up to 95% volume reduction) can be achieved using the melting method that involves heating the expanded polystrene to a very high temperature to compress the product. This type of reycling involved a hot element that needed to remain powered throughout the day, and this proved to be very energy inefficient and posed safety hazards due to the off-gassing of chemicals.On-and-off operation of the machine can be a big waste of energy and time because of cooling and re-heating of the machine.

Q: What is the price for compacted EPS?

A: China is the biggest market for compacted EPS in the world. The CIF Hong Kong price for compacted EPS will ranges from around US$200 to US$500 per ton but is very much dependent on location, cleanliness, level of compaction and current market situation. Contaminants such as seafood waste, oils, excess moisture, ice, malodors and the presence of paper/plastic labels can generate problems for recycling and reduce the prices to be paid.

Q: Do I need an EPS compactor?

A: Businesses with regular quantities of EPS waste should consider the use of compactors to initially reduce the volume of EPS that is thrown away, which in turn could save money by reducing the number of times the bin requires emptying.
For a company with around 20 tons of EPS per year, the payback period for a compacting machine costing around US$5,000 can be as short as one years, if the compacted EPS is sold to a recycling company for about US$200 per ton and the costs of disposal to landfill are saved.
For companies with a large volume of EPS waste, it may be cost-effective to establish an in-house EPS compaction facility, to supply EPS recyclers direct.

Q: Can all kind of waste EPS be recycled?

A: No. If you want to recycle any EPS, please make sure it is clean, with no stickers, grease, dirt, tape, labels, etc. If it’s too difficult to remove a label or contaminant, simply break off the offending piece and recycle the rest. The recycler will chop up the EPS anyway and turn it into new packing material.

Q: What is the market for recycled polystyrene?

A: Almost half of the EPS recycled is remanufactured into EPS packaging. Other applications for EPS recycling include building applications such as siding and deck board, ceiling texture, molding, electronic products, auto products, agricultural products, office supplies, egg cartons, and beanbag filler. Markets for non-foam PS include coat hangers, picture frames, waste baskets, videocassettes, flowerpots, and nursery trays.

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