analysis can be a useful tool for assessing thepotential benefits of recycling programmes. If recycled otherwise have been made from new (virgin) polymer,this will directly reduce oil usage and emissions ofgreenhouse gases associated with the production ofthe virgin polymer (less the emissions owing to therecycling activities themselves). However, if plasticsare recycled into products that were previously madefrom other materials such as wood or concrete, thensavings in requirements for polymer production willnot be realized (Fletcher & Mackay 1996). Theremay be other environmental costs or benefits of anysuch alternative material usage, but these are a distrac-tion to our discussion of the benefits of recycling andwould need to be considered on a case-by-case basis.Here, we will primarily consider recycling of plasticsinto products that would otherwise have beenproduced from virgin polymer.Feedstock (chemical) recycling technologies satisfythe general principle of material recovery, but aremore costly than mechanical recycling, and lessenergetically favourable as the polymer has to be depo-lymerized and then re-polymerized. Historically, thishas required very significant subsidies because of thelow price of petrochemicals in contrast to the highprocess and plant costs to chemically recycle polymers.Energy recovery from waste plastics (by transform-ation to fuel or by direct combustion for electricitygeneration, use in cement kilns and blast furnaces,etc.) can be used to reduce landfill volumes, butdoes not reduce the demand for fossil fuels (as thewaste plastic was made from petrochemicals;Garforth et al. 2004). There are also environmentaland health concerns associated with their emissions.One of the key benefits of recycling plastics is toreduce the requirement for plastics production.Table 3 provides data on some environmental impactsfrom production of virgin commodity plastics (up to the ‘factory gate’), and summarizes the ability of theseresins to be recycled from post-consumer waste. Interms of energy use, recycling has been shown tosave more energy than that produced by energy recov-ery even when including the energy used to collect,transport and re-process the plastic (Morris 1996).Life-cycle analyses has also been used for plastic-recycling systems to evaluate the net environmentalimpacts (Arena et al. 2003; Perugini et al. 2005) andthese find greater positive environmental benefits formechanical recycling over landfill and incinerationwith energy recovery.It has been estimated that PET bottle recycling givesa net benefit in greenhouse gas emissions of 1.5 tonnesof CO2-e per tonne of recycled PET (Department ofEnvironment and Conservation (NSW) 2005) as wellas reduction in landfill and net energy consumption.An average net reduction of 1.45 tonnes of CO2-e pertonne of recycled plastic has been estimated as auseful guideline to policy (ACRR 2004), one basis forthis value appears to have been a German life-cycleanalysis (LCA) study (Patel et al. 2000), which alsofound that most of the net energy and emission benefitsarise from the substitution of virgin polymer pro-duction. A recent LCA specifically for PET bottlemanufacture calculated that use of 100 per centrecycled PET instead of 100 per cent virgin PETwould reduce the full life-cycle emissions from 446 to327 g CO2 per bottle, resulting in a 27 per cent relativereduction in emissions (WRAP 2008e).Mixed plastics, the least favourable source of recycledpolymer could still provide a net benefit of the vicinity of0.5 tonnes of CO2-e per tonne of recycled product(WRAP 2008c). The higher eco-efficiency for bottlerecycling is because of both the more efficient processfor recycling bottles as opposed to mixed plastics andthe particularly high emissions profile of virgin PET pro-duction. However, the mixed plastics recycling scenariostill has a positive net benefit, which was consideredsuperior to the other options studied, of both landfillsand energy recovery as solid refuse fuel, so long asthere is substitution of virgin polymer.5. PUBLIC SUPPORT FOR RECYCLINGThere is increasing public awareness on the need forsustainable production and consumption. This hasencouraged local authorities to organize collection ofrecyclables, encouraged some manufacturers todevelop products with recycled content, and otherbusinesses to supply this public demand. Marketingstudies of consumer preferences indicate that there isa significant, but not overwhelming proportion ofpeople who value environmental values in their pur-chasing patterns. For such customers, confirmationof recycled content and suitability for recycling ofthe packaging can be a positive attribute, while exag-gerated claims for recyclability (where the recyclabilityis potential, rather than actual) can reduce consumerconfidence. It has been noted that participating inrecycling schemes is an environmental behaviour thathas wide participation among the general populationand was 57 per cent in the UK in a 2006 survey(WRAP 2008d ), and 80 per cent in an Australiansurvey where kerbside collection had been in placefor longer (NEPC 2001).Some governments use policy to encourage post-consumer recycling, such as the EU Directive onpackaging and packaging waste (94/62/EC). Thissubsequently led Germany to set-up legislation forextended producer responsibility that resulted in thedie Gru ¨ne Punkt (Green Dot) scheme to implementrecovery and recycling of packaging. In the UK,producer responsibility was enacted through a schemefor generating and trading packaging recovery notes,plus more recently a landfill levy to fund a range ofwaste reduction activities. As a consequence of all theabove trends, the market value of recycled polymerand hence the viability of recycling have increasedmarkedly over the last few years.Extended producer responsibility can also beenacted through deposit-refund schemes, 塑料回收英文文献和中文翻译(6):http://www.youerw.com/fanyi/lunwen_31406.html