塑料回收英文文献和中文翻译(2)
Ryan et al. 2009; Teut en et al.2009; Thompson et al. 2009b).Recycling is clearly a waste-management strategy,but it can also be seen as one current example ofimplementing the concept of industrial ecology,whereas in a natural ecosystem there are no wastesbut only products (Frosch & Gallopoulos 1989;McDonough & Braungart 2002). Recycling of plasticsis one method for reducing environmental impact andresource depletion. Fundamentally, high levels ofrecycling, as with reduction in use, reuse and repair orre-manufacturing can allow for a given level of productservice with lower material inputs than would otherwisebe required. Recycling can therefore decrease energyand material usage per unit of output and so yieldimproved eco-efficiency (WBCSD 2000). Although,it should be noted that the ability to maintain whateverresidual level of material input, plus the energy inputsand the effects of external impacts on ecosystemswill decide the ultimate sustainability of the overallsystem.In this paper, we will review the current systems andtechnology for plastics recycling, life-cycle evidencefor the eco-efficiency of plastics recycling, and brieflyconsider related economic and public interest issues.We will focus on production and disposal of packagingas this is the largest single source of waste plastics inEurope and represents an area of considerable recentexpansion in recycling initiatives.2. WASTE MANAGEMENT: OVERVIEWEven within the EU there are a wide range of waste-management prioritizations for the total municipalsolid waste stream (MSW), from those heavilyweighted towards landfill, to those weighted towardsincineration (figure 1)—recycling performance alsovaries considerably. The average amount of MSWgenerated in the EU is 520 kg per person per yearand projected to increase to 680 kg per person peryear by 2020 (EEA 2008). In the UK, total use ofplastics in both domestic and commercial packagingis about 40 kg per person per year, hence itforms approximately 7–8% by weight, but a largerproportion by volume of the MSW stream (WasteWatch 2003).Broadly speaking, waste plastics are recovered whenthey are perted from landfills or littering. Plasticpackaging is particularly noticeable as litter becauseof the lightweight nature of both flexible and rigidplastics. The amount of material going into thewaste-management system can, in the first case, bereduced by actions that decrease the use of materials inproducts (e.g. substitution of heavy packaging formatswith lighter ones, or downgauging of packaging).Designing products to enable reusing, repairing orre-manufacturing will result in fewer products enteringthe waste stream.Once material enters the waste stream, recycling isthe process of using recovered material to manufacturea new product. For organic materials like plastics, theconcept of recovery can also be expanded to includeenergy recovery, where the calorific value of thematerial is utilized by controlled combustion as afuel, although this results in a lesser overall environ-mental performance than material recovery as it doesnot reduce the demand for new (virgin) material.This thinking is the basis of the 4Rs strategy in wastemanagement parlance—in the order of decreasingenvironmental desirability—reduce, reuse, recycle(materials) and recover (energy), with landfill as theleast desirable management strategy.It is also quite possible for the same polymer tocascade through multiple stages—e.g. manufactureinto a re-usable container, which once entering thewaste stream is collected and recycled into a durableapplication that when becoming waste in its turn, isrecovered for energy.Table 1. Consumption of plastics and waste generation bysector in the UK in 2000 (Waste Watch 2003).usage waste arisingktonne (%) ktonne (%)packaging 1640 37 1640 58commercial andindustrial490household 1150building and construction 1050 24 284 10structural 800 49non-structural 250 235electrical and electronics 355 8 200 7furniture and housewares 335 8 200a7automotive and transport 335 8 150 5agriculture and horticulture 310 7 93 3other 425 10 255a9total 4450 2820aestimate (a) LandfillLandfill is the conventional approach to waste man-agement, but space for landfills is becoming scarce insome countries. A well-managed landfill site resultsin limited immediate environmental harm beyond theimpacts of collection and transport, although thereare long-term risks of contamination of soils andgroundwater by some additives and breakdown by-products in plastics, which can become persistentorganic pollutants (Oehlmann et al. 2009; Teutenet al. 2009). A major drawback to landfills from a sus-tainability aspect is that none of the material resourcesused to produce the plastic is recovered—the materialflow is linear rather than cyclic.