Plastic wastes – Reduce, Reuse and Recycle of plastics are essential to make environment greener and safer:
1. Introduction - We find considerable growth in use of plastic everywhere due to various beneficial properties of plastics, such as:
(a) Extreme versatility and ability to be tailored to meet very specific technical needs.
(b) Lighter weight than competing materials, reducing fuel consumption during transportation.
(c) Extreme durability.
(d) Resistance to chemicals, water and impact.
(e) Better safety and hygiene properties for food packaging.
(f) Excellent thermal and electrical insulation properties.
(g) Relatively inexpensive to produce.
However, plastics waste creates lot of nuisances and degrade environment in a big way.
2. Pollution problems of plastics - Industrial practices in plastic manufacture can lead to polluting effluents and the use of toxic intermediates, the exposure to which can be hazardous. Better industrial practices have led to minimizing exposure of plant workers to harmful fumes.
There is growing concern about the excess use of plastics, particularly in packaging. This has been done, in part, to avoid the theft of small objects. The use of plastics can be reduced through a better choice of container sizes and through the distribution of liquid products in more concentrated form. A concern is the proper disposal of waste plastics. Litter results from careless disposal, and decomposition rates in landfills can be extremely long. Consumers should be persuaded or required to divert these for recycling or other environmentally acceptable procedures. Marine pollution arising from disposal of plastics from ships or flow from storm sewers must be avoided.
Recycling of plastics is desirable because it avoids their accumulation in landfills. While plastics constitute only about 8 percent by weight or 20 percent by volume of municipal solid waste, their low density and slowness to decompose makes them a visible pollutant of public concern. It is evident that the success of recycling is limited by the development of successful strategies for collection and separation. Recycling of scrap plastics by manufacturers has been highly successful and has proven economical, but recovering discarded plastics from consumers is more difficult.
3. Factors affecting recycling of plastics - Recycling and re-utilization of waste plastics have several advantages. Recycling and re-utilization of waste plastics lead to a reduction of the use of virgin materials and of the use of energy, thus also a reduction of carbon dioxide emissions. Economically, in some cases, plastics recycling may be profitable. However, a number of factors can complicate the practice of plastics recycling, such as the collection of the plastics waste, separation of different types of plastics, cleaning of the waste and possible pollution of the plastics. A further complicating factor is the low-value nature of most of the products that can be manufactured from recycled plastics. Reusing plastic is preferable to recycling as it uses less energy and fewer resources.
4. Advantages of reuse and recycle of plastics – It has been observed, to reduce bad effects of waste plastics, it is better to recycle and re-utilize waste plastics in environment-friendly manners. As per statistics, about 80% of post-consumer plastic waste is sent to landfill, 8% is incinerated and only 7% is recycled. In addition to reducing the amount of plastics waste requiring disposal, recycling and reuse of plastic can have several other advantages, such as:
(i) Conservation of non-renewable fossil fuels – Plastic production uses 8% of the world’s oil production, 4% as feedstock and 4% during manufacture.
(ii) Reduced consumption of energy.
(iii) Reduced amounts of solid waste going to landfill.
(iv) Reduced emissions of carbon-dioxide (CO2), nitrogen-oxides (NOx) and sulfur-dioxide (SO2).
5. Plastic bags and their nuisances - Plastic bags are popular with consumers and retailers as they are a functional, lightweight, strong, cheap, and hygienic way to transport food and other products. Most of these go to landfill and garbage heaps after they are used, and some are recycled. Once littered, plastic bags can find their way on to our streets, parks and into our waterways. Although plastic bags make up only a small percentage of all litter, the impact of these bags is nevertheless significant. Plastic bags create visual pollution problems and can have harmful effects on aquatic and terrestrial animals. Plastic bags are particularly noticeable components of the litter stream due to their size and can take a long time to fully break down. Many carrier bags end up as unsightly litter in trees, streets, parks and gardens which, besides being ugly, can kill birds, small mammals and other creatures. Bags that make it to the ocean may be eaten by sea turtles and marine mammals, who mistake them for jellyfish, with disastrous consequences. In developed countries billion bags are thrown away every year, most of which are used only once before disposal. The biggest problem with plastic bags is that they do not readily break down in the environment. It has been found that, the average plastic carrier bag is used for five minutes, but takes 500 years to decompose.
Plastic bags are made from ethylene, a gas that is produced as a by-product of oil, gas and coal production. Ethylene is made into polymers (chains of ethylene molecules) called polyethylene. This substance, also known as polyethylene or polythene, is made into pellets which are used by plastic manufacturers to produce a range of items, including plastic bags.
Plastics can be broadly split into two groups, those that consist of long strands (thermo softening) and those that also contain short cross-links (thermosetting). Thermo softening plastic will deform when heated and can be remolded into new shapes. Thermosetting plastics are much stronger, but once they have been formed into a shape, they will hold that shape indefinitely, and if heated they will merely burn.
Recycle and reuse of plastic bags can mitigate environmental problems.
6. Issues relating to plastics – There are about 50 different groups of plastics, with hundreds of different varieties. All types of plastic are recyclable. To make sorting and thus recycling easier, the American Society of Plastics Industry developed a standard marking code to help consumers identify and sort the main types of plastic. Before recycling, plastics are sorted according to their resin identification code.The type of plastics (as per the resin identification code) and their most common uses are given below:
a. Plastic process scrap recycling - Currently most plastic recycling in of the developed countries are of ‘process scrap’ from industry, i.e. polymers left over from the production of plastics. This is relatively simple and economical to recycle, as there is a regular and reliable source and the material is relatively uncontaminated. This is usually described as reprocessing rather than recycling.
b. Post-use plastic recycling – Post-use plastic can be described as plastic material arising from products that have undergone a first full service life prior to being recovered. Households are the biggest source of plastic waste, but recycling household plastics presents a number of challenges. One of these relates to collection.
c. Mechanical recycling - Mechanical recycling of plastics refers to processes which involve the melting, shredding or granulation of waste plastics. Plastics must be sorted prior to mechanical recycling. Mostly, sorting is done manually. Recently, technology is being introduced to sort plastics automatically, using various techniques such as X-ray fluorescence, infrared and near infrared spectroscopy, electrostatics and flotation. Following sorting, the plastic is either melted down directly and molded into a new shape, or melted down after being shredded into flakes and than processed into granules called re-granulate.
d. Chemical or feedstock recycling – Feedstock recycling describes a range of plastic recovery techniques to make plastics, which break down polymers into their constituent monomers, which in turn can be used again in refineries, or petrochemical and chemical production. A range of feedstock recycling technologies is currently being explored. These include: (i) Pyrolysis, (ii) Hydrogenation, (iii) Gasification and (iv) Thermal cracking.
Feedstock recycling has a greater flexibility over composition and is more tolerant to impurities than mechanical recycling, although it is capital intensive and requires very large quantities of used plastic for reprocessing to be economically viable.
7. Strategies for reduction of Environmental Impact of Plastics -
(a) Reduce the use - Source reduction Retailers and consumers can select products that use little or no packaging. Select packaging materials that are recycled into new packaging – such as glass and paper. If people refuse plastic as a packaging material, the industry will decrease production for that purpose, and the associated problems such as energy use, pollution, and adverse health effects will diminish.
(b) Reuse containers - Since refillable plastic containers can be reused for many times, container reuse can lead to a substantial reduction in the demand for disposable plastic and reduced use of materials and energy, with the consequent reduced environmental impacts. Container designers will take into account the fate of the container beyond the point of sale and consider the service the container provides.
(c) Require producers to take back resins – Get plastic manufacturers directly involved with plastic disposal and closing the material loop, which can stimulate them to consider the product’s life cycle from cradle to grave. Make reprocessing easier by limiting the number of container types and shapes, using only one type of resin in each container, making collapsible containers, eliminating pigments, using water-dispersible adhesives for labels, and phasing out associated metals such as aluminum seals. Container and resin makers can help develop the reprocessing infrastructure by taking back plastic from consumers.
(d) Legislatively require recycled content – Requiring that all containers be composed of a percentage of post-consumer material reduces the amount of virgin material consumed.
(e) Standardize labeling and inform the public – Standardized labels for “recycled,” “recyclable,” and “made of plastic type X” must be developed for easy identification.
8. Conclusion – Lots of innovations in recycling of waste plastics have been introduced in many countries. We have to see, we should not pollute environment while going for recycling and use of recycled products.