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Basics of recycling : 

Basics of recycling


Outline 1. Types of recyclable materials 2. Biodegradable plastics


1. Types of recyclable materials Plastic Types 1 and 2 are commonly recycled. Type 4 is less commonly recycled. The other types are generally not recycled, except perhaps in small test programs. Common plastics polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) do not have recycling numbers. The code must be molded into the plastic item. The symbol should be easily visible for sorting purposes. The best symbols are large with a different surface finish than the surrounding plastic. If the container has a matte surface (rough), then the symbol should be smooth, a smooth container should have a rough recycling symbol.


* Type 1 - PETE Polyethylene Terephthalate (PET) Soda & water containers, some waterproof packaging. * Type 2 - HDPE High-Density Polyethylene Milk, detergent & oil bottles. Toys and plastic bags. * Type 3 - V Vinyl/Polyvinyl Chloride (PVC) Food wrap, vegetable oil bottles, blister packages. * Type 4 - LDPE Low-Density Polyethylene Many plastic bags. Shrink wrap, garment bags. * Type 5 - PP Polypropylene Refrigerated containers, some bags, most bottle tops, some carpets, some food wrap. * Type 6 - PS Polystyrene Throwaway utensils, meat packing, protective packing. * Type 7 - OTHER Usually layered or mixed plastic. No recycling potential - must be landfilled.


Glass, Steel, Aluminum Cans and Foil Glass, steel (or "tin") and aluminum are easy to recognize and recycle. For clarity, a recycling symbol should be present, but most people have little trouble sorting these materials. Glass bottles must not be mixed with other types of glass such as windows, light bulbs, mirrors, glass tableware, Pyrex or auto glass. Ceramics contaminate glass and are difficult to sort out. Clear glass is the most valuable. Mixed color glass is near worthless, and broken glass is hard to sort. There have been marketing experiments with plastic and steel cans that look exactly like aluminum cans. Recycling plants have been damaged by these fakes. The distinctive shape of an aluminum beverage can must be reserved for aluminum beverage cans only. It is no longer necessary to remove labels for recycling. To save water, clean only enough to prevent odors. Unlike with plastics, the high temperature of glass and metal processing deals easily with contamination. Scrap aluminum is accepted in many places. Other metals are rarely accepted.


Aseptic Packaging (Drink boxes, soy-milk containers) The square boxes used for liquids are called "Aseptics", the most common brand of which is "Tetra Pak". Aseptics are made from complex layers of plastic, metal and paper. The actual recycling process, unfortunately, is very expensive and awkward, and is therefore only available in a very few places. Coca-Cola maintains a list of aseptic recyclers, call 1-800-888-6488 for information. Because of the difficulties, only an insignificant fraction of aseptic packages are currently recycled.


Paper Most types of paper can be recycled. Newspapers have been recycled profitably for decades, and recycling of other paper is growing. Virgin paper pulp prices have soared in recent years prompting construction of more plants capable of using waste paper. They key to recycling is collecting large quantities of clean, well-sorted, uncontaminated and dry paper.


Rechargeable Batteries (other than car batteries) Rechargable batteries are commonly used in portable telephones, computers, power tools, shavers, electric toothbrushes, radios, video tape recorders and other consumer products. There are a variety of different battery types, some of which contain quite toxic materials.   The Rechargeable Battery Recycling Corporation is an industry funded group promoting battery recycling. Manufacturers pay a fee to use the logo, and to support the costs of the eventual collection of the batteries they sell. Look for (and even insist on seeing) the RBRC logo on rechargable batteries you buy.


Motor Oil, Tires and Car Batteries All three of these products are big environmental problems, but all three are easily recycled. Used motor oil contains heavy metals and other toxic substances, and is considered hazardous waste. Each year do-it-yourself oil changers improperly dump more oil than the tanker Exxon Valdez spilled into Alaska's Prince William Sound. One quart of oil can kill fish in thousands of gallons of water. Motor oil containers should mention the danger of used oil to humans and the environment.


Where to bring things for recycling? More information on recycling:


2. Biodegradable plastics


Biodegradation of polyethylene There are several ways to enhance the environmental degradation of polyethylene. Increased photodegradability is obtained by copolymerization of carbonyl groups directly into the backbone (ethylene/carbon monoxide) or in the side chains (vinyl ketone copolymers) of the polyethylene. Another way to increase the photodegradability is to add photosensitizing additives, like organosoluble metal ions or sulfur-complexed metal ions (Scott-Gilead formulation). Thermal degradation and/or photodegradation is enhanced if prooxidants containing transition-metal ions are used alone or together with starch (Griffin process). Some transitionmetal compounds, e.g., iron and manganese, have a powerful catalytic effect on radical formation from hydroperoxides leading to rapid molecular weight reduction by breakdown of the intermediate alkoxyl radicals.

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