polythene pollution final submission
TRANSCRIPT
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