Polythene Pollution Final Submission

POLYTHENE POLLUTION INTRODUCTION Pollution from Polythene In this age of computers and Internet, Use and Throw culture is the order of the day. You use anything and after using it, throw it away. Polythene pollution has drastically disturbed everyman’s life style. Polythene material can be seen spread over in the streets, in the neighborhood, in the rivulets, river-banks of the small or big rivers. Even Ganga, Yamuna and other rivers all are covered with a thick layer of polythene material.. Degradation of polyethne is a great challenge as the materials are increasingly used. Ignorance of the people who don’t care about the effects of proper waste disposal and who may not know about the effects of improper waste disposal. They therefore dump the polythene bags carelessly. Emphasis should be put on the use of paper bags. This is because the paperbags are also light and they can easily decompose, Globalization has added to this problem in a big way. Electronic gadgets all are designed with a view to use and throw, because the repairs are costly. In USA and other western countries Garbage disposal problem has reached a horrifying level. But they have developed a meticulous system of garbage disposal with periodical review. In India we have to prepare ourselves for this gigantic onslaught of pollution. Enough is enough! We need to be disciplined and we must cultivate civic sense to save India from this disaster. In order to fight the menace of Polythene pollution, the Local Self Government institutions

have come up with laws restricting the use of polythene. But the menace of polythene continues unabated. In fact it is no use thrusting such laws which are not practical. But they do not face such problems as we face in India. There are strict laws for the disposal of the polythene bags. The polythene, after use, is dumped at the garbage disposal pots or Trashes. There are different garbage disposal pots for dumping polythene, paper orother waste material.

There is strict enforcement of laws which provides for punitive

measures if garbage is thrown at unspecified places. The citizens comply with the rules with responsibility. But in India there is no enforcement of law, with the result the entire road or the Mohalla becomes the Garbage disposal place. We as citizen have a responsibility towards this burning problem. We should use the polythene material but must throw the same at specified garbage disposal pots. A vigilant public opinion can only fight the problems arising out of the use of polythene, for which we all must owe responsibility seriously. Trillions of polythene bags are used world over every year. They persist on this earth to haunt us and our generations for centuries.Polythene chokes the drains, the water bodies, pollute the land and poison us slowly but

surely.

Even

mowed

grass

cannot

escape

the

polythene

menace.Polythene has been recovered from the rumen of countless cattle and is a major threat to animals also.Polythene pollution is an epidemic now.Polythene is indestructible. One particle of polythene is further made of many particles. If we continue to use polythene, the earth would become polluted on an alarming rate.

DESCRIPTION

Polyethylene is a polymer consisting of long chains of the monomer ethylene (IUPAC name ethane). The recommended scientific name polyethene is systematically derived from the scientific name of the monomer [1][2]. In certain circumstances it is useful to use a structure-based nomenclature; in such cases IUPAC recommends poly (methylene) [2] (poly(methanediyl) is an non-preferred alternative [3][4]). The difference in names between the two systems is due to the opening up of the monomer's double bond upon polymerisation.In the polymer industry the name is sometimes shortened to PE in a manner similar to that by which other polymers like polypropylene and polystyrene are shortened to PP and PS respectively. In the United Kingdom the polymer is commonly called polythene, although this is not

recognized scientifically. The ethene molecule (known almost universally by its common name ethylene) C2H4 isCH2=CH2, Two CH2 groups connected by a double bond Plastic is one of the few new chemical materials which pose environmental problem. Polyethylene, polyvinyl chloride, polystyrene is largely used in the manufacture of plastics. Synthetic polymers are easily molded into complex shapes, have high chemical resistance, and are more or less elastic. Some can be formed into fibers or thin transparent films. These properties have made them popular in many durable or disposable goods and for packaging materials. These materials have molecular weight ranging from several thousands to 1,50,000. Excessive molecular size seems to be mainly responsible for the resistance of these chemicals to biodegradation and their persistence in soil environment for a long time. Plastic in the environment is regarded to be more an aesthetic nuisance than a hazard, since the material is biologically quite inert. The plastic industry in the US alone is $ 50 billion per year and is obviously a tempting market for biotechnology gical enterprises. Biotechnological processes are being developed as an alternative to existing route or to get new biodegradable biopolymers. 20% of solid municipal wastes in US is plastic. Non-degradable plastics accumulate at the rate of 25 million tonnes per year. According to an estimate more than 100 million tonnes of plastic is produced every year all over the world. In India it is only 2 million tonnes. In

India use of plastic is 2 kg per person per year while in European countries it is 60 kg per person per year while that in US it is 80 kg per person per year.

HISTORY Polyethylene was first synthesized by the German chemist Hans von Pechmann who prepared it by accident in 1898 while heating diazomethane. When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy, substance that he had created they recognized that it contained

long

-CH2-

chains

and termed

it

polymethylene.The

first

industrially practical polyethylene synthesis was discovered (again by accident) in 1933 by Eric Fawcett and Reginald Gibson at the ICI works in Northwich, England.[5] Upon applying extremely high pressure (several hundred atmospheres) to a mixture of ethylene and benzaldehyde they again produced a white, waxy, material. Because the reaction had been initiated by trace oxygen contamination in their apparatus the experiment was, at first, difficult to reproduce. It was not until 1935 that another ICI chemist, Michael Perrin,developed this accident into a reproducible high-

pressure synthesis for polyethylene that became the basis for industrial LDPE production

beginning

in

1939.Subsequent

landmarks

in

polyethylene

synthesis have revolved around the development of several types of catalyst that promote ethylene polymerization at more mild temperatures and pressures. The first of these was a chromium trioxide-based catalyst discovered in 1951 by Robert Banks and J. Paul Hogan at Phillips Petroleum. In 1953 the German chemist Karl Ziegler developed a catalytic system based on titanium halides and organoaluminium compounds that worked at even milder conditions than the Phillips catalyst. The Phillips catalyst is less expensive and easier to work with, however, and both methods are used in industrial practice.Biodegradable plastics are plastics that will decompose in natural

aerobic

(composting)

and

anaerobic

(landfill)

environments.

Biodegradation of plasticscan be achieved by enabling microorganisms in the environment to metabolize themolecular structure of plastic films to produce an inert humus-like material that is less harmful to the environment. They may be composed of either bioplastics,which are plastics whose components are derived from renewable raw materials, or petroleum-based plastics which utilize an additive. The use of bio-active compounds compounded with swelling agents ensures that, when combined with heat and moisture, they expand the plastic's molecular structure and allow the bio-active compounds to metabolizes and neutralize the plastic.Biodegradable plastics typically are produced in two forms: injection molded (solid, 3D shapes), typically in the

form of disposable food service items, and films, typically sold as collection bags for leaves and grass trimmings, and agricultural mulch.

CAUSES OF PLASTIC POLLUTION

Plastics are used because they are easy and cheap to make and they can last a long time. Unfortunately these same useful qualities can make plastic a huge pollution problem. Because the plastic is cheap it gets discarded easily and its persistence in the environment can do great harm. Urbanization has added to the plastic pollution in concentrated form in cities. Plastic thrown on land can enter into drainage lines and chokes them resulting into floods in local areas in cities as experienced in Mumbai, India in 1998. It was claimed in one of the programmes on TV Channel that eating plastic bags results in death of 100 cattles per day in U.P. in India. In

stomach of one dead cow, as much as 35 kg of plastic was found. Because plastic does not decompose, and requires high energy ultra-violet light to break down, the amount of plastic waste in our oceans is steadily increasing. More than 90% of the articles found on the sea beaches contained plastic. The plastic rubbish found on beaches near urban areas tends to originate from use on land, such as packaging materials used to wrap around other goods, remote rural beaches the rubbish tends to have come from ships, such as fishing equipment used in the fishing industry. This plastic can affect marine wildlife in two important ways: by entangling creatures, and by being eaten. Turtles are particularly badly affected by plastic pollution, and all seven of the world's turtle species are already either endangered or threatened for a number of reasons. Turtles get entangled in fishing nets, and many sea turtles have been found dead with plastic bags in their stomachs. Turtles mistake floating transparent plastic bags for jellyfish and eat them. In one dead turtle found off Hawaii in the Pacific more than 1000 pieces of plastic were found in the stomach. A recent US report concluded that more than 100000 marine mammals die each year in the world's oceans by eating or becoming entangled in plastic rubbish, and the position is worsening World-wide, 75 marine bird species are known to eat plastic articles. This includes 36 species found off South Africa. A recent study of blue petrel chicks at South Africa's remote Marion Island showed that 90% of chicks examined had plastic in their stomachs apparently fed to them accidentally by their parents. South African seabirds are among the worst

affected in the world. Plastics may remain in the stomachs, blocking digestion and possibly causing starvation.

PROBLEMS POLLUTION

CAUSED

DUE

TO

POLYTHENE

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; for example, there have been problems in the past resulting from workers being exposed to toxic vinyl chloride vapor during the production of polyvinyl chloride. Much progress has been made in developing "green processes" that avoid the use of detrimental substances. For example, phosgene, a toxic "war gas," was formerly used in the manufacture of polycarbonates. New processes, now almost universally

employed, eliminate its use. Also, the "just in time" approach to manufacture has been made possible by computer-controlled processes, whereby no significant amounts of intermediates are stored, but just generated as needed. In addition, efforts are ongoing to employ "friendly" processes involving enzyme-catalyzed low-temperature methods akin to biological reactions to replace more polluting high-temperature processes involving operations like distillation. Spillage of plastic pellets that find their way into sewage systems, and eventually to the sea, has hurt wildlife that may mistake the pellets for food. Better "housekeeping" of plastic molding facilities is being enforced in an attempt to address this problem. Most plastics are relatively inert biologically, and they have been employed in medical devices such as prosthetics, artery replacements, and "soft" and interocular lenses. Problems with their use largely result from the presence of trace amounts of nonplastic components such as monomers and plasticizers. This has led to restrictions on the use of some plastics for food applications, but improved technology has led to a reduction in the content of such undesirable components. For example, the use of polyacrylonitrile for beverage bottles was banned at one time because the traces of its monomer, acrylonitrile, were a possible carcinogen. However, current practices

render

it

acceptable

today.

There

has

been

concern

about endocrine disruption from phthalate-containing plasticizers used for plastics such as polyvinyl chloride (PVC). The subject of this possible side effect is controversial,

Post-Consumer Plastic Waste, 2000 (Adapted from Oak Ridge National Laboratory.)

PROBLEMS IN HUMANS People are exposed to these chemicals not only during manufacturing, but also by using plastic packages, because some chemicals migrate from the plastic packaging to the foods they contain. Examples of plastics contaminating food have

been reported with most plastic types, including Styrene from polystyrene, plasticizers from PVC, antioxidants from polyethylene, and Acetaldehyde from PET. Among the factors controlling migration are the chemical structure of the migrants and the nature of the packaged food. In studies cited in Food Additives and Contaminants, LDPE, HDPE, and polypropylene bottles released measurable levels of BHT, Chimassorb 81, Irganox PS 800, Irganix 1076, and Irganox 1010 into their contents of vegetable oil and ethanol. Evidence was also found that acetaldehyde migrated out of PET and into water. Recommendations

Find alternatives to plastic products whenever possible. Some specific suggestions: * Buy food in glass or metal containers; avoid polycarbonate drinking bottles with Bisphenol A * Avoid heating food in plastic containers, or storing fatty foods in plastic containers or plastic wrap. * Do not give young children plastic teethers or toys * Use natural fiber clothing, bedding and furniture * Avoid all PVC and Styrene products •

Buy food in glass or metal containers

•

Avoid heating food in plastic containers, or storing fatty foods in plastic containers or plastic wrap

•

Do not give young children plastic teethers or toys

•

Use natural fiber clothing, bedding and furniture

•

Avoid all PVC and Styrene products

Plastic

Common Uses

Adverse Health Effects

Polyvinyl chloride (#3PVC)

Food packaging, plastic wrap, containers for toiletries, cosmetics, crib bumpers, floor tiles, pacifiers, shower curtains, toys, water pipes, garden hoses, auto upholstery, inflatable swimming pools

Can cause cancer, birth defects, genetic changes, chronic bronchitis, ulcers, skin diseases, deafness, vision failure, indigestion, and liver dysfunction

Phthalates (DEHP, DINP, and others)

Softened vinyl products manufactured with phthalates include vinyl clothing, emulsion paint, footwear, printing inks, non-mouthing toys and children’s products, product packaging and food wrap, vinyl flooring, blood bags and tubing, IV containers and components, surgical gloves,

Endocrine disruption, linked to asthma, developmental and reproductive effects. Medical waste with PVC and phthalates is regularly incinerated causing public health effects from the release of dioxins and mercury, including cancer, birth defects, hormonal changes, declining sperm counts, infertility, endometriosis, and immune system

breathing tubes, general purpose labware, inhalation masks, many other medical devices

impairment.

Polycarbonate, with Bisphenol A (#7)

Water bottles

Scientists have linked very low doses of bisphenol A exposure to cancers, impaired immune function, early onset of puberty, obesity, diabetes, and hyperactivity, among other problems (Environment California)

Polystyrene

Many food containers for meats, fish, cheeses, yogurt, foam and clear clamshell containers, foam and rigid plates, clear bakery containers, packaging "peanuts", foam packaging, audio cassette housings, CD cases, disposable cutlery, building

Can irritate eyes, nose and throat and can cause dizziness and unconsciousness. Migrates into food and stores in body fat. Elevated rates of lymphatic and hematopoietic cancers for workers.

insulation, flotation devices, ice buckets, wall tile, paints, serving trays, throw-away hot drink cups, toys Polyethelyne (#1 PET)

Water and soda bottles, carpet fiber, chewing gum, coffee stirrers, drinking glasses, food containers and wrappers, heatsealed plastic packaging, kitchenware, plastic bags, squeeze bottles, toys

Suspected human carcinogen

Polyester

Bedding, clothing, disposable diapers, food packaging, tampons, upholstery

Can cause eye and respiratory-tract irritation and acute skin rashes

Ureaformaldehyde

Particle board, plywood, building insulation, fabric finishes

Formaldehyde is a suspected carcinogen and has been shown to cause birth defects and genetic changes. Inhaling formaldehyde can cause cough,

swelling of the throat, watery eyes, breathing problems, headaches, rashes, tiredness Polyurethane Foam

Cushions, mattresses, pillows

Bronchitis, coughing, skin and eye problems. Can release toluene diisocyanate which can produce severe lung problems

Acrylic

Clothing, blankets, carpets made from acrylic fibers, adhesives, contact lenses, dentures, floor waxes, food preparation equipment, disposable diapers, sanitary napkins, paints

Can cause breathing difficulties, vomiting, diarrhea, nausea, weakness, headache and fatigue

Tetrafluoroethelyne

Non-stick coating on cookware, clothes irons, ironing board covers, plumbing and tools

Can irritate eyes, nose and throat and can cause breathing difficulties

THE THREAT TO WILDLIFE This plastic can affect marine wildlife in two important ways: by entangling c reatures, and by being eaten. Turtles: Turtles

are

particularly

badly

affected

by

plastic

pollution, and all seven of the world's turtle species are already either endangered or threatened for a number of reasons. Turtles get entangled in fishing nets, and many sea turtles have been found dead with plastic bags in their stomachs. It is believed they mistake these floating semi-transparent bags for jellyfish and eat them. The turtles die from choking or from being unable to eat. One dead turtle found off Hawaii in the Pacific was found to have more than 1000 pieces of plastic in its stomach including part of a comb, a toy truck wheel and nylon rope. Marine Mammals: There is great concern about the effect of plastic rubbish on marine mammals in particular, because many of these creatures are already under threat for a variety of other

reasons e.g. whale populations have been decimated by uncontrolled hunting. A recent US report concluded that 100 000 marine mammals die each year in the world's oceans by eating or becoming entangled in plastic rubbish, and the position is worsening.When a marine mammal such as a Cape fur seal gets caught up in a large piece of plastic, it may simply drown, or become exhausted and die of starvation due to the greater effort needed to swim, or the plastic may kill slowly over a period of months or years as it bites into the animal causing wounds, loss of blood and/or severing of limbs. "Ghost Nets": A large number of marine creatures become trapped and killed in "ghost nets". These are pieces of gill nets which have been lost by fishing vessels. Other pieces of fishing equipment such as lobster pots may also keep trapping creatures. Marine Birds: World-wide, 75 marine bird species are known to eat plastic articles. This includes 36 species found off South Africa. A recent study of blue petrel chicks at South Africa's remote Marion Island showed that 90% of chicks examined had plastic in their stomachs apparently fed to them accidentally by their parents. South African seabirds are among the worst affected in the world. Plastics may remain in the stomachs, blocking digestion and possibly causing starvation. As particular

species seem to be badly affected this may be a threat to whole populations of these birds.

Plastics cause Health Problems in Monkeys Researchers at the Yale School of Medicine have linked a chemical found in everyday plastics to problems with brain function and mood disorders in monkeys -the first time the chemical has been connected to health problems in primates. The study is the latest in an accumulation of research that has raises concerns about bisphenol A, or BPA, a compound that gives a shatterproof quality to polycarbonate plastic and has been found to leach from plastic into food and water. The Yale study comes as federal toxicologists yesterday reaffirmed an earlier draft report finding that there is "some concern" that bisphenol A can cause developmental problems in the brain and hormonal systems of infants and children. "There remains considerable uncertainty whether the changes seen in the animal studies are directly applicable to humans, and whether they would result in clear adverse health effects," John R. Bucher, associate director of the National Toxicology Program, said in a statement. "But we have concluded that the possibility that BPA may affect human development cannot be dismissed."

PLASTIC BABY BOTTLES WASHINGTON - A chemical used to make baby bottles and other shatterproof plastic containers could be linked to a range of hormonal problems, a preliminary government report has found. The report was greeted by some environmental groups as confirmation of their concerns, while chemical makers latched on to the report’s preliminary nature

and

its

authors’

warning

against

drawing

overly

worrisome

conclusions. The federal National Toxicology Program said Tuesday that experiments on rats found precancerous tumors, urinary tract problems and early puberty when the animals were fed or injected with low doses of the plastics chemical bisphenol A.

CONTROLLING PLASTIC POLLUTION Reduced Use and Recycling 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. Disposal at sea is prohibited by federal regulation.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. It is well recognized that separated plastics can be recycled to yield more superior products than possible for mixed ones. Labeling plastic items with symbols has been employed, which enables consumers to identify them easily for placement in separate containers for curbside pickup. However, success depends on how conscientious consumers are in employing such standards and the ability of collectors to keep various types of plastic separate.

Even a small amount of a foreign plastic in recycling feedstock can lead to the appreciable deterioration of properties, and it is difficult to achieve a high degree of purity. Manual sorting at recycling centers helps, but even trained sorters have difficulty identifying recyclables. Furthermore, manual sorting is an unattractive task and retaining labor willing to be trained for this is problematic. Automatic sorting techniques have been developed that depend on various physical, optical, or electronic properties of plastics for identification. Such methods prove difficult because of the variety of sizes, shapes, and colors of plastic objects that are encountered. Although in principle it is possible to create devices that can separate plastics with varying degrees of success, the equipment generally becomes more expensive with increasing efficiency. Technology for this continues to improve, and it is becoming possible to successfully separate mixed plastics derived from curbside pickup using such equipment. To separate plastics, it is first necessary to identify the different types as indicated in the table. One must also distinguish between thermoplastics and thermosets. The latter, as found in tires and melamine dishes, has molecules that are interconnected by "crosslinks" and cannot be readily melted for recycling unless they are chemically reduced to low-molecular-weight species. For tires, recycling has not proved economical so disposal has involved grinding them up as asphalt additives for roads or burning in cement kilns.Over 1.5 million pounds of plastic bottles were recycled in 2000, representing a four-fold increase in the amount of plastic recycled the previous decade. Nonetheless, the capacity to recycle bottles appreciably exceeds their supply by about 40 percent, so local governments and environmental groups

need

to

encourage

greater

participation

in

this

practice

among

consumers.Profitable operations are currently in place for recycling polyethylene

terephthalate (PET) from bottle sources and converting it into products such as fibers. One persistent problem, though, is obtaining clean enough feedstock to avoid the clogging of orifices in spinnerets by foreign particles. This has limited the ability to produce fine denier fibers from such sources. PET recycling is also constrained by regulations limiting its use to produce items in contact with food because there had been concern about contamination in consideration of improved recycling techniques.A leading candidate for recycle feedstock is carpets because replacement carpets are usually installed by professionals able to identify recyclables and who serve as a ready source for recycling operations. They face the problem, however, of separating the recyclable carpet components from other parts such as jute backing and dirt. Such recycling operations have been only marginally profitable.Polystyrene (PS) is another potentially recyclable polymer, but identifying a readily collectable source is problematic. One had been the Styrofoam "clamshells" fast-food chains use to package hamburgers. Recyclers were able to profitably collect polystyrene from such sources and produce salable products. However, largely because of public pressure, this use of polystyrene has

Major Types of Plastics by S.P.I. Codes and Types of Plastic Packaging. ( Modern Plastics, January, 1992 )

declined, so related recycling practices have largely disappeared too. Cafeteria items from school lunchrooms are another potential, but the collection of such objects involves the development of an infrastructure, often not in place. In these cases, it is necessary to separate the polystyrene from paper and food waste, but washing and flotation techniques have been developed for this purpose. Increasing amounts of plastic components appear in automobiles, and their recovery from junked cars is a possibility. Its success depends on the ability of a prospective "junker" to identify and separate the plastic items. Three efforts may aid in this accomplishment:

1. The establishment of databases to enable junkers to learn what kinds of plastic are used in what parts of what model cars. 2. A reduction in the number of different plastics used for car construction. 3. The design of cars such that plastic parts may be removed easily (this would require special types of fasteners). This illustrates a general need—the design of plastic-containing products with the ability to recycle in mind. As a consequence of public concern about the environmental problems arising from plastic use, industry is responding to these needs. The effort continues to use fewer different kinds of plastics and to adopt designs that allow for easier recycling but still retain desirable properties. There are, however, some worthwhile products that can be produced from mixed plastic, such as "plastic lumber" used for picnic benches and marine applications such as docks and bulkheads that successfully replace wooden lumber which often contains toxic preservatives and arsenic. But, the market for such a product is limited, so efforts to obtain separated plastics are preferred.

Using Degradable Plastics Discarded plastics are hard to eliminate from the environment because they do not degrade and have been designed to last a long time. It is possible to design polymers containing monomer species that may be attacked by chemical, biological, or photochemical action so that degradation by such means will occur

over a predetermined period of time. Such polymers can be made by chemical synthesis (as with polylactic acid) or through bacterial or agricultural processes (as with the polyalkonates). Although such processes are often more expensive than conventional ones, cost would undoubtedly drop with increased production volume. One success story was the introduction of carbonyl groups into polyethylene by mixing carbon monoxide with ethylene during synthesis. These carbonyl groups are chomophores that lead to chain breaking upon the absorption of ultraviolet light. The polymer is then broken down into small enough units that are subject to bacterial attack. This approach has been successful, for example, in promoting the disappearance of rings from beverage cans, which are potentially harmful to wildlife. A problem with the degradation of plastics is that it is probably undesirable in landfills because of the leachants produced that may contaminate water supplies. It is better in these instances to ship the plastics to composting facilities. This requires the separation of degradable plastics from other materials and the availability of such facilities. In most cases, the infrastructure needed for such an approach is not in place. This has discouraged its use for disposable diapers that are said to constitute 1 to 2 percent of landfill volume. Degradable polymers may have limited use in the reduction of litter and production of flushable plastics, for example, feminine hygiene products, but it seems unlikely that the use of such materials will be a viable means of disposal for large amounts of plastic products. Degradation leads to the loss of most of the potential energy content of plastics that might be recovered by trash-to-energy procedures.

Converting Trash to Energy A method of plastic disposal with more positive environmental implications is burning and recovering the energy for power generation or heating. Plastics contain much of the energy potential of the petroleum from which they are made, and they, in a sense, are just borrowing this energy that may be recovered when the plastic is burned. Environmentalists and the public have objected to this procedure, leading to legislative restrictions. This has arisen, in part, because of the image of "oldfashioned" incinerators polluting the air with toxic fumes and ash. However, it is possible to construct a "high-tech" incinerator designed to operate at appropriate temperatures and with sufficient air supply that these problems are minimized. Remaining toxic substances in fumes may be removed by scrubbing, and studies have shown that no significant air pollution results. Toxic ash, for the most part, does not arise from the polymer components of the feedstock, but rather from other materials mixed with the polymers as well as from fillers, catalyst content, and pigments associated with the polymers. Proper design of the polymers and crude separation of the incinerator feedstock can reduce this problem. Furthermore, if the feedstock was not incinerated but placed in landfills, contaminants would ultimately enter the environment in an uncontrolled way. Incineration reduces the volume, so that the ash, which may contain them, can be disposed of under more controlled conditions. Also, it is possible to insolublize the ash by converting it into a cement like material that will not readily dissolve. Facilities for converting trash to energy in an environmentally acceptable way are expensive and at present not cost-effective when considering short-range funding. However, in the long run, they are environmentally desirable and reduce the need

for alternative means for plastic waste disposal. It is imperative that legislators and taxpayers soon adopt this long-range perspective.

Processing of Bioplastics Presence of nucleating agents (which facilitate crystallization) or the use of plasticiser shortens the processing cycles during the moulding operations. There are two main points about processing of PHBV bioplastics - (i) The limited thermal stability of the polymer and so it degrades rapidly above 195 degree centi. (ii) The need to optimise conditions to allow a maximum crystallization rate (which reduces cycle times). The maximum rate of crystallization is reported to be at about 55-60 degree centi. which is significantly closer to Tg than the Tm. Processing temperatures should not exceed 180 degree centi. and duration of time when the material is in melt state should be kept minimum. At the end of a run the processing equipment should be purged with polyethylene. When blow moulding the blow-pin and the mould should be at about 60 degree centi. to optimise crystallisation rates. Similarly injection moulds are recommended at 55-65 degree centi. The lowhydroxyvalerate, unplasticised grades are most critical to process, requiring the higher processing temperatures. Conditions are slightly less critical with the higher hydroxyvalerate containing and plasticised grades. In addition to producing PHAs in dry powder form for melt processing, Metabolix is also developing PHA latexes. These materials have unique film forming properties, which are finding application in higher performance applications as well as in more traditional commodity uses. Metabolix company supplies PHA samples to companies under research and development agreements.

CONSERVATION ACTION The problem of plastic pollution is serious and requires further urgent study. Immediate action is also required such as : •

Reduction of the amount of plastic used in packaging which is usually immediately thrown away. Re-use of plastics should be encouraged.

•

Plastic wrapping and bags should carry a warning label stating the dangers of plastic pollution, and shoppers should be encouraged to use their own bags, or recycled paper bags.

WHAT YOU CAN DO •

Buy products with less Plastic packaging and tell store Personnel why you are doing so. Shoppers should use their own bags or recycled paper bags.

•

Support recycling schemes and promote support for one in your local area.

•

Fishermen throughout South Africa should not throw away waste line, net or plastic litter - this causes huge suffering and many deaths.

•

Practice and promote proper disposal of plastics in your home and at the beach. Always remember that litter generates litter. Never dispose of plastics in the sewage system.

•

At the beach dispose of plastics and other litter in the bins provided. If these facilities are inadequate, contact the local authority responsible and lodge a complaint. Take your litter back home with you if there are no receptacles on

the beach. Pick up any plastic litter you may see on the beach or in rock pools in the vicinity in which you are sitting or walking. Encourage young children to do likewise. •

In the street never throw plastic or other litter out of your car or drop it on the pavement or in the gutter.

•

Set an example to others and encourage them to help. Plastics are not themselves a problem. They are useful and popular materials which can be produced with relatively little damage to the environment. The problem is the excessive use of plastics in one-off applications together with careless disposal