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At the moment about 1.5 million Tonnes of plastic are being recycled yearly, 75% of which is polyethylene, both low density (LDPE) and high density (HDPE). Recycling of plastic film so far one is of the weakest points in all recycling schemes. The reason for this failure is that post-consumer plastic film waste is usually a mixture of diverse plastics, specially polyethylene (LDPE, HDPE) and polypropylene (PP), all together comprising 95% of the total film. Although cleaning and separation of the polyolefins (LDPE, HDPE and PP) from the rest is easy using flotation or hydrocycloning methods, individualisation of LDPE, HDPE and PP is difficult, since their respective densities are very similar while their variable shape do not allow the use of automated, sensor-based methods (such as use of near-infrarred detection).
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As previously stated, the market for plastic film in Europe is around 5 million tonnes, from which 4.75 million tonnes correspond to polyolefins, with current projections indicating a yearly rise of 2.45% at least up to 2013. From this amount, it is estimated that 3 million tonnes could be collected at municipal separation facilities, corresponding approximately to 2.14 million tonnes LDPE, 0.53 million tonnes HDPE and 0.33 million tonnes PP. Mechanical recycling rate of these materials is just about 107 thousand tonnes year, 3.5% of the total, usually in mixed form for low added-value applications since mixed polyolefins can not be used in high demand, high added value applications such as film blowing, the most extended process for film production, due to the intrinsic inhomogeneity of the material which results in poor behaviour under the high stresses characteristic of this processing method. Current market prices for mixed polyolefin film wastes, suitable only for injection moulding is 180 Euros/tonne, being very difficult to find purchasers. In turn, market price for recycled LDPE, separated and suitable for film blowing is 481 Euro/Ton, about half the price of virgin material, with much larger market demand than material currently available. There exists at the moment no technology which can separate the LDPE component from mixed polyolefin film wastes. |
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