Societal benefits of plastics
(a) Improved consumer health and safety
Plastics contribute to the health and safety of consumers in food and water packaging applications. Water has become a critical focus in urban areas, and plastics provide the mechanism for the supply and storage of clean drinking water. Additionally, plastics are lightweight, easy to manufacture and are installed in a range of diverse water control and distribution systems (e.g. sewerage, storm water, land drainage and irrigation). Plastic food packaging allows safe, time-dependent storage of fresh produce and other food, using temperature and atmosphere control inside the package (using gas-flush packaging and oxygen scavenger technology). In addition, the quality of packaged foods (especially time–temperature history) can be monitored with low-cost indicator labels built into the packaging (M. A. Neal 1990–1995, personal communication).
Using plastics in transportation building and even packaging applications invariably results in very significant savings in materials and in fossil fuel energy. For example, a comprehensive study published in January 2005, GUA (Gesellschaft für umfassende Analysen GmbH) established that packaging beverages in PET versus glass or metal reduces energy consumption by 52% (83.2 GJ yr−1 in Europe alone). Greenhouse gas emissions were reduced 55% on the same basis (4.3 million tonnes CO2 eq yr−1 in Europe). Use of lighter plastic composites in place of metal in the design of newer aircraft results in significant fuel cost savings as well as easier assembly. The new Boeing 787, for instance, will have a skin that is 100 per cent composite and an interior that is 50 per cent plastic composite, allowing it to deliver an expected 20 per cent savings in fuel costs. In the automotive sector, the replacement of metal components by plastic composites that weigh less than 50 per cent of the original contributes to significant energy savings. Aluminium can also be replaced with plastic components that are 50 per cent lighter at a 20–30% saving in cost. For example, the average plastic content of a light vehicle has increased to 110 kg or approximately 12 per cent of its weight.
In a recent study, the energy expenditure in manufacturing a disposable foamed polystyrene cup was found to be much lower than that for a ceramic cup or a disposable paper cup. When cleaning is factored in, in terms of energy use, it would take several hundred uses for a reusable ceramic cup to match that associated with a single-use expanded polystyrene cup. A similar study by the Dutch Research Institute TNO (2007) confirmed Hocking's findings.
Plastics have the advantage of a high strength-to-weight ratio, allowing minimal material usage (and low cost) in packaging desig. On average, plastic packaging accounts for between 1 and 3 per cent of the total product weight. For instance, it takes 2 g of plastic film to package 200 g of cheese; 1.5 l of liquid can be safely stored in a 38 g bottle and a tub containing 125 g of yoghurt weighs only 4.5 g. The ecological balance sheet of plastic packaging, i.e. the sum total of the corresponding energy consumption for production, transport and disposal and other effects on the environment, is often superior to that of competing materials. For example, in one study, in switching from gable-top milk cartons manufactured from a paper/aluminium/plastic composite to plastic pouches, the energy saving in production of the package was estimated to be 72 per cent, a 50 per cent saving in refrigeration space contributed to further energy savings and the waste stream to landfill was reduced by 90 per cent.
The development of renewable energy resources is likely to rise as a consequence of increasing oil prices. Solar and wind power, geothermal heat and biomass are inexhaustible. Already, some regions in Europe are using renewable energy to meet most of their heating, hot water and electricity requirements, and Iceland exploits its geothermal energy. Plastics as a material can drive innovative designs to support this effort. For instance, modern solar water heaters containing plastics such as PE and PVC can provide up to 65 per cent of a household's annual hot water demand. Photovoltaic collectors that convert solar energy into electricity can cover the remaining energy requirements of a house. The use of these technologies would be impossible without plastics' light weight, mouldability, UV resistance and insulation properties.
Plastics capture around half of the carbon that is used to produce them, and this is a valuable resource. The properties of plastics make them inherently recyclable at several different levels. Multiple strategies of reuse of products, post-consumer recycling, resource recovery in the form of fuels or chemicals and energy recovery via incineration are all applicable to plastics waste, provided adequate waste management practices can be adopted. Recycling is clearly an energy-saving strategy; most primary recycling and the post-consumer recycling of high-value plastics make economic and environmental sense and greatest benefits are realized when recycling is viewed as a material conservation strategy. Mixed streams of plastics waste can be difficult to recycle. Here waste-to-energy via incineration allows the high heat value of the post-consumer plastics to be recaptured for use. The latter strategy is more advantageous than with most other packaging, as plastics have higher energy content than paper.
In most countries, as the available landfill space becomes limited, both materials recycling and resource or energy recovery will become increasingly attractive solid-waste management options. For example, in Korea, household waste material from everyday life and economic activities has decreased substantially, from 1.3 kg per person per day in 1994 to 1.04 kg in 2002, and the rate of overall material recycling exceeded that of landfilling for the first time in 2002.
According to industrial sources (PlasticsEurope 2008), in Europe, the collection of waste plastics for conventional recycling was 4.4 million tonnes in 2006, with approximately 12 per cent of this being traded (exported) with Asia. A plastic product with an exceptionally high level of recycling is the plastic bottle. Plastic bottles can be made of PET, PE, PP or PVC, and according to Petcore (2007), 40 per cent of all PET bottles available for collection were recycled in the EU in 2006. This amounts to 1.1 million tonnes yr−1.
The versatility of the recycling approaches available for post-consumer plastics is summarized in figure 4. The horizontal sequence indicates the main steps in the product chain: feedstock acquisition, resin manufacture and fabrication and use of the product, each associated with an energy Ei. The reuse of manufacturing waste in the same product (regrind use) (A) is a routine cost-saving step presently practised in plastic product fabrication. Post-consumer waste can either be refabricated into other products (usually of lower value) (B) or chemically treated and/or heat-treated to form a feedstock (C). Each recycling strategy, however, has an energy EA, EB, EC associated with it; depending on the comparison of energy demand for recycling with Ei for the main steps in the production and consumption sequence, energy savings via recycling can be readily computed.
Plastics and the future
As suggested by the futurist Hammond (2007) in his recent publication ‘The World in 2030’, the speed of technological development is accelerating exponentially and, for this reason, by the year 2030, it will seem as if a whole century's worth of progress has taken place in the first three decades of the twenty-first century. In many ways, life in 2030 will be unrecognizable compared with life today. During this time, plastics will play a significantly increased role in our lives. Plastics are already becoming ‘smart’ and will likely serve numerous important roles in future living, including human tissue or even organ transplants, key materials used in ultra-low-emission lightweight cars and aircraft, superior insulation for homes that run on photovoltaic technology based on plastic collectors, reusable electronic graphic media for books or magazines, smart packaging that monitors food content continuously for signs of spoilage and high-efficiency solid-state lighting based on plastic organic diode technology. As petroleum reserves become more limited, new varieties of plastics are likely to increasingly be made from renewable biomass. These will contribute to the already extensive array of mechanical and aesthetic performance properties that plastics are well known for. Any future scenario where plastics do not play an increasingly important role in human life therefore seems unrealistic.
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