Wednesday, March 4, 2015

Recycling of plastics-New approach to save water and energy

To day's world cannot live without plastics as practically every walk of life is associated with use of one or the other plastic material. Out of the 300 million tons production of plastics of different types world wide, about one third is used for packing,  rest being channeled into a variety of products like tubes, pipes, structural parts, sheets, containers etc. In India more than 40% goes for packaging including that for protecting foods. As they are derived from non-renewable fossil fuels, man must be wondering whether his head-on rushing into massive use of plastics will prove to be a folly, considering that world was using for centuries traditional materials like metal, glass, ceramics, wood etc all of which are readily recyclable endlessly and with relative ease, besides being renewable in nature. Plastics, which are high molecular organic molecules are impervious to water and are not degradable in nature for hundreds of years. Recycling of plastics can be done by just melting it after sorting and cleaning at relatively low temperatures but there is a limit as to how many times it can be recycled as its property is adversely affected after recycling. Conventional recycling involves use of high quantity of water and lot of energy, both at a premium in countries like India. A new technology reported from Mexico claims that the water consumption and energy use can be significantly reduced making the recycled plastic.cheaper. Here is a take on this new development.    

"Mexican startup Ak Inovex has developed a 'Greener' plastic recycling uses no water and only half the energy  At the same time, it produces plastic pellets of equal or better quality,  resulting in an environmentally friendlier process that also promises to be significantly cheaper. Plastic recycling can turn discarded bottles and other scrap into a myriad of useful objects, helping produce anything from polyester clothes to 3D printing filaments and even diesel. However, it is a long, laborious affair that consumes plenty of resources  –  especially water. Among other things, the plastic needs to be thoroughly washed to get rid of impurities, carefully dehydrated inside an oven, and then water-cooled once again as the newly-formed plastic filaments are cut into small pellets. According to Marco Adame, the new method that his startup has come up with can produce pellets of equal or better quality using just half of the energy by getting rid of the need for these temperature extremes, while also doing away with the need for water altogether. The system uses special walls that, on contact, are able to both mold the plastic into the desired pellet shape and cool those pellets at the same time. The energy-demanding dehydration process, which involves temperatures of around 180° C (360° F), had been a necessity so far because, after being washed, the plastic molecules would otherwise attract water to themselves and prevent the plastic from crystallizing properly. Being able to process scrap plastic without water has therefore simplified things considerably. Adame says that using his technique, the same machines are able to process styrofoam, polystyrene and ABS, which together make up about 90 percent of all plastics. The improved versatility would mean less space would be needed for operation."

Limitation vis-a-vis plastic recycling does not lie in technology but logistical problems associated with segregating different plastics from the garbage for channeling them to different recycling systems. There are at least two dozens of plastics in common use and they come to the garbage dump mixed with organic and biological waste and this restricts the extent of plastic recycling to less than 5% of total used through out the world, the figure varying from country to country. Increased use of plastic wastes for energy generation is another encouraging development that will remove more and more of these naturally indestructible man-made material from the environment. Comparing to paper which is recycled to the extent of 80% plastics will have to go a long way to remove the tag it has earned as "chokers" for its role in contaminating oceans and river bodies, bringing about destruction of natural aquatic creatures.


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