coveringfor example, beverage containers, batteries and vehicletyres. These schemes can be effective in boostingcollection rates, for example one state of Australiahas a container deposit scheme (that includes PETsoft-drink bottles), as well as kerbside collectionschemes. Here the collection rate of PET bottles was74 per cent of sales, compared with 36 per cent ofsales in other states with kerbside collection only.The proportion of bottles in litter was reduced aswell compared to other states (West 2007).6. ECONOMIC ISSUES RELATINGTO RECYCLINGTwo key economic drivers influence the viability ofthermoplastics recycling. These are the price of therecycled polymer compared with virgin polymer andthe cost of recycling compared with alternative formsof acceptable disposal. There are additional issuesassociated with variations in the quantity and qualityof supply compared with virgin plastics. Lack of infor-mation about the availability of recycled plastics, itsquality and suitability for specific applications, canalso act as a disincentive to use recycled material.Historically, the primary methods of waste disposalhave been by landfill or incineration. Costs of landfillvary considerably among regions according to theunderlying geology and land-use patterns and can influ-ence the viability of recycling as an alternative disposalroute. In Japan, for example, the excavation that isnecessary for landfill is expensive because of the hardnature of the underlying volcanic bedrock; while inthe Netherlands it is costly because of permeabilityfrom the sea. High disposal costs are an economicincentive towards either recycling or energy recovery.Collection of used plastics from households is moreeconomical in suburbs where the population density issufficiently high to achieve economies of scale. Themost efficient collection scheme can vary with locality,type of dwellings (houses or large multi-apartmentbuildings) and the type of sorting facilities available.In rural areas ‘bring schemes’ where the public delivertheir own waste for recycling, for example when theyvisit a nearby town, are considered more cost-effectivethan kerbside collection. Many local authorities andsome supermarkets in the UK operate ‘bring banks’, or even reverse-vending machines. These lattermethods can be a good source of relatively pure recycl-ables, but are ineffective in providing high collectionrates of post-consumer waste. In the UK, dramaticincreases in collection of the plastic bottle wastestream was only apparent after the relatively recentimplementation of kerbside recycling (figure 2).The price of virgin plastic is influenced by the priceof oil, which is the principle feedstock for plastic pro-duction. As the quality of recovered plastic is typicallylower than that of virgin plastics, the price of virginplastic sets the ceiling for prices of recovered plastic.The price of oil has increased significantly in the lastfew years, from a range of around USD 25 per barrelto a price band between USD 50–150 since 2005.Hence, although higher oil prices also increase thecost of collection and reprocessing to some extent,recycling has become relativelymore financially attractive.Technological advances in recycling can improvethe economics in two main ways—by decreasing thecost of recycling (productivity/efficiency improve-ments) and by closing the gap between the value ofrecycled resin and virgin resin. The latter point isparticularly enhanced by technologies for turningrecovered plastic into food grade polymer by removingcontamination—supporting closed-loop recycling.This technology has been proven for rPET fromclear bottles (WRAP 2008b), and more recentlyrHDPE from milk bottles (WRAP 2006).So, while over a decade ago recycling of plasticswithout subsidies was mostly only viable from post-industrial waste, or in locations where the cost ofalternative forms of disposal were high, it is increas-ingly now viable on a much broader geographicscale, and for post-consumer waste.7. CURRENT TRENDS IN PLASTIC RECYCLINGIn western Europe, plastic waste generation is growingat approximately 3 per cent per annum, roughly inline with long-term economic growth, whereas theamount of mechanical recycling increased strongly ata rate of approximately 7 per cent per annum. In2003, however, this still amounted to only 14.8 percent of the waste plastic generated (from all sources).Together with feedstock recycling (1.7 per cent) andenergy recovery (22.5 per cent), this amounted to atotal recovery rate of approximately 39 per cent fromthe 21.1 million tonnes of plastic waste generated in2003 (figure 3). This trend for both rates of mechanicalrecycling and energy recovery to increase is continuing,although so is the trend for increasing waste generation.8. CHALLENGES AND OPPORTUNITIES FORIMPROVING PLASTIC RECYCLINGEffective recycling of mixed plastics waste is the nextmajor challenge for the plastics recycling sector. Theadvantage is the ability to recycle a larger proportionof the plastic waste stream by expanding post-consumer collection of plastic packaging to cover awider variety of materials and pack types. Productdesign for recycling has strong potential to assist insuch recycling efforts. A study carried out in the UKfound that the amount of packaging in a regular shop-ping basket that, even if collected, cannot be effectivelyrecycled, ranged from 21 to 40% (Local GovernmentAssociation (UK) 2007). Hence, wider implementationof policies to promote the use of environmental designprinciples by industry could have a large impact onrecycling performance, increasing the proportion ofpackaging that can economically be collected andperted from landfill (see Shaxson et al. 2009). Thesame logic applies to durable consumer goods designingfor disassembly, recycling and specifications for use ofrecycled resins are key actions to increase recycling.Most post-consumer collection schemes are for rigidpackaging as flexible packaging tends to be problematicduring the collection and sorting stages. Most currentPhil. Trans. R. Soc. B (2009) material recovery facilities have difficulty handling flex-ible 塑料回收英文文献和中文翻译(7):http://www.youerw.com/fanyi/lunwen_31406.html