Tuesday, January 1, 2013

Plastic recycling

Plastics have become an integral part of our lives. Plastic constitutes about 12% of Municipal solid wastes generated in USA,a sharp increase from just 1% in 1960 to the current level. Increasing usage of plastics have created environmental issues such as increased energy and water usage, emission of greenhouse gases and finally waste disposal and health issues. Many countries are now trying to reduce the waste disposal problems by reducing usage, recovering fuels from plastics and recycling.However a large quantity of plastics are still returned to landfills creating long term health problems. According to EPA : • 31 million tons of plastic waste were generated in 2010, representing 12.4 percent of total MSW. • In 2010, the United States generated almost 14 million tons of plastics as containers and packaging, almost 11 million tons as durable goods, such as appliances, and almost 7 million tons as nondurable goods, for example plates and cups. • Only 8 percent of the total plastic waste generated in 2010 was recovered for recycling. • In 2010, the category of plastics which includes bags, sacks, and wraps was recycled at almost 12 percent. • Plastics also are found in automobiles, but recycling of these materials is counted separately from the MSW recycling rate. How Plastics Are Made : Plastics can be divided in to two major categories: thermosets and thermoplastics. A thermoset solidifies or “sets” irreversibly when heated. They are useful for their durability and strength, and are therefore used primarily in automobiles and construction applications. Other uses are adhesives, inks, and coatings. A thermoplastic softens when exposed to heat and returns to original condition at room temperature. Thermoplastics can easily be shaped and molded into products such as milk jugs, floor coverings, credit cards, and carpet fibers. According to the American Chemistry Council, about 1,800 US businesses handle or reclaim post-consumer plastics. Plastics from MSW are usually collected from curbside recycling bins or drop-off sites. Then, they go to a material recovery facility, where the materials are sorted into broad categories (plastics, paper, glass, etc.). The resulting mixed plastics are sorted by plastic type, baled, and sent to a reclaiming facility. At the facility, any trash or dirt is sorted out, then the plastic is washed and ground into small flakes. A flotation tank then further separates contaminants, based on their different densities. Flakes are then dried, melted, filtered, and formed into pellets. The pellets are shipped to product manufacturing plants, where they are made into new plastic products. Resin Identification Code The resin identification coding system for plastic, represented by the numbers on the bottom of plastic containers, was introduced by SPI, the plastics industry trade association, in 1988. Municipal recycling programs traditionally target packaging containers, and the SPI coding system offered a way to identify the resin content of bottles and containers commonly found in the residential waste stream. Plastic household containers are usually marked with a number that indicates the type of plastic. Consumers can then use this information to determine whether or not certain plastic types are collected for recycling in their area. Contrary to common belief, just because a plastic product has the resin number in a triangle, which looks very similar to the recycling symbol, it does not mean it is collected for recycling. SPI Resin Identification Code 1 2 3 4 5 6 7 Type of Resin Content PET HDPE Vinyl LDPE PP PS OTHER • PET - Polyethylene Terephthalate • HDPE - High-density Polyethylene • LDPE - Low-density Polyethylene • PP - Polypropylene • PS - Polystyrene • Other - Mixed Plastics Markets for Recovered Plastics: Markets for some recycled plastic resins, such as PET and HDPE, are stable and even expanding in the United States. Currently, the US has the capacity to be recycling plastics at a greater rate. The capacity to process post-consumer plastics and the market demand for recovered plastic resin exceeds the amount of post-consumer plastics recovered from the waste stream. The primary market for recycled PET bottles continues to be fiber for carpet and textiles, while the primary market for recycled HDPE is bottles, according to the American Chemistry Council. Looking forward, new end uses for recycled PET bottles might include coating for corrugated paper and other natural fibers to make waterproof products like shipping containers. PET can even be recycled into clothing, such as fleece jackets. Recovered HDPE can be manufactured into recycled-content landscape and garden products, such as lawn chairs and garden edging. Source Reduction: Source reduction is the process of reducing the amount of waste that is generated. The plastics industry has successfully been able to reduce the amount of material needed to make packaging for consumer products. Plastic packaging is generally more lightweight than its alternatives, such as glass, paper, or metal. Lighter weight materials require less fuel to transport and result in less material in the waste stream. Source : EPA. Attribution to :Online Education.net.