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 CAUSED DUE TO POLYTHENE POLLUTION

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

Polyvinylchloride(#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,

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

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

immune system 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 insulation, flotation devices, ice buckets, wall tile, paints, serving trays, throw-away hot drink cups, toys

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.

Polyethelyne(#1 PET)

Water and soda bottles, carpet fiber, chewing gum, coffee stirrers, drinking glasses, food containers and wrappers, heat-sealed 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

Urea-formaldehyde

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

PolyurethaneFoam

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

Can cause breathing difficulties, vomiting,

acrylic fibers, adhesives, contact lenses, dentures, floor waxes, food preparation equipment, disposable diapers, sanitary napkins, paints

diarrhea, nausea, weakness, headache and fatigue

Tetrafluoro-ethelyne

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 PlasticsDiscarded 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 "old-fashioned" 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 low-hydroxyvalerate, 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