Advent of fossil fuel based plastics has literally revolutionized the material foundation of the industrial world and there is no area of manufacturing which is untouched by plastics. Progress in plastic material development has made it possible to make plastics which are as strong as steel while soft plastics find extensive use as containers and bags. Though the convenience and cost factors have pitchforked plastics as the most preferred material of choice till recently, a rethinking about its impact on environment and sustainability is slowly putting a brake on its continued use. While cheap petroleum fuels from which most plastics are derived was justification enough to introduce them in place of traditional materials like glass and metals, this argument cannot hold any more since the cost of non-renewable fossil fuels increased several fold during the last 3 decades.
Plastics attracted severe criticism from the environmentalists because of its lack of biodegradability credentials. It is known that plastic materials take any where from 100 to 1000 years to degrade when used in landfills besides polluting air and water around. Land availability will pose a challenge in many countries if landfill practice is continued and restrictions are now being put in place to curtail this approach. Besides extremely thin plastic bags made from less than 20 micron thick films are choking the drains of many cities causing uncontrolled floods during rainy season. Plastics in garbage are estimated to be killing a million creatures in the sea every year. Littering with plastic bags has become such a nuisance that many countries have banned use of thin plastic bags by the consumer industry during retail sales of products. In some countries incentive schemes are in place for using packaging modes of sustainable nature. Free supply of plastic bags by the retail industry is sought to be discouraged through pricing the same so that consumers are dissuaded from using them. In some countries consumers are encouraged to bring their own bags while many retail stores provide facilities for collection of used plastics for sending to recycling plants.
In India also some of the states are in the forefront in banning plastic bags by grocery stores but implementation lacks the necessary teeth though such a process is bound to take time to assume critical level of efficiency. Surprisingly there is a silent consumer awareness about the adverse impact of plastics on the society and many of them are voluntarily shunning the use on their own without any compulsion. The biggest challenge for the objective of weeding out plastics is posed by lack of infrastructure in most places to segregate plastics from urban wastes generated from the garbage. It is true that in countries in Europe and others like the US there are well designed garbage segregation and collection facilities that enable easy recycling but such an approach is conspicuous by its absence in countries like India and most of the developing world. Unless this is done used plastics will continue to pose problem to the society at large.
While used plastics are often considered a waste, the facts reveal otherwise and it is not realized that throwing a plastic bag has much more connotation than any consumer realizes. Why is that many have come to the conclusion that used plastics must be recycled? There are strong reasons which include constraint on resources, conservation of energy, saving landfill space and avoiding environmental degradation. It is not realized that one ton of plastics, if recycled can save one ton of fossil fuel and it can spare more than 7 cubic meter of land space used for landfill. Recycling thus becomes an economic option and this is realized more by the industry which has led to increased demand for recycled plastics. More and more retailers and branded product companies are in the market looking for high quality recycled plastics. Many of them have already introduced pet bottles containing high percentage of recycled components with less and less virgin polymer. The UK dairy industry is reported to be committed to use up to 50% recycled HDPE in their bottles by 2020. To day about 22% of recycled HDPE plastics is used by the pipe manufacturers while 55% of recycled PET is used by the textile industry. Food industry is slow to catch up with the trend because of the rigid migration limits set for food contact application.
Recycling process is not as simple as one thinks because of the complex chemical and physical science involved in the process. Generally plastics have a low entropy of mixing because of high molecular weight and heating alone cannot ensure dissolving such large molecules. Similarly plastics have to be nearly identical in composition for the process to be efficient as different plastics if melted together can be vulnerable to phase separation with the phase boundaries susceptible to structural weakness. Presence of dyes, fillers and other additives make the recycling process more difficult as the melt becomes too viscous for removing them easily. Beverage bottles and plastic bags, however contain less additives and therefore are preferred for recycling. Sorting out as per Resin Identification Code of the Society of Plastic Industry can make the cycling much more easier.
An added incentive for the industry to look for recycled plastics is the carbon credits they will be able to get by shunning virgin polymeric materials. According to industry sources demand for recycled plastics will far exceed the production that can be achieved by the recycling industry and such a situation will make the recycled products somewhat costlier. Still user industries prefer them because of compulsions to reduce the carbon footprint of the manufacturing and retailing sector as a whole and to achieve increased resource efficiency in the coming years.
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