About Plastic Pollution

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 bio degradation 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 biotechnological enterprises. Biotechnological processes are being developed as an alternative to existing route or to get new biodegradable bio-polymers . 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.

Processing of Bio-plastics

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 bio-plastics - (i) The limited thermal stability of the polymer and so it degrades rapidly above 195 degree centi. (ii) The need to optimize 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.

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 programmers on TV Channel that eating plastic bags results in death of 100 cattle's 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 material used to wrap around other goods. 

THE SOLUTIONS FOR PLASTIC

Plastics may be either (a) photodegradable or (b) semi-biodegradable or (c) 100% biodegradable. Photodegradable plastics have light sensitive groups incorpora ted directly into backbone of the polymer as additives. This produces non-degradable smaller fragments which cause loss of material integrity. Example of semibiodegradable plastic can be blends of starch and polyethylene. PHB is an example of 100% biodegradable plastic. Approximately a dozen of inherently biodegradable plastics are now in the market, with range of properties suitable for various consumer products. Some examples of biodegradable films or other raw material (for biodegradable plastic articles) made by different companies are - 

(1) BASF - Ecoflex - for biodegradable garbage bags - made up of polyester
building blocks that offer properties similar to LDPE (10000 tonnes production
plant at Ludwigshafen, Germany.
(2) Bayer - BAKbiodegradable polyester amide. - contains ester and amide groups
similar to that in nature.- therefore biodegradable.
(3) Dupont's - BioMax
(4) Eastman's - EasterBio
(5) Cargill-Dow's - EcoPla
All of them are targetting market of 70000 tonnes by 2001.
(6) Arrow Coated Products Ltd. (ACPL) has started bioplastic watr soluble film
production in India in Gujrat State at Ankleshwar. But capacity is only 600
tonnes per annum. They do not export any of it.
(7) Om Engineers (India) - have also tested and about to introduce LDPE
modified biodegradable film (for which they have applied for patent even.
(8) Fasalex, The Institute for AgroBiotechnology, Kopfig, Austria have developed biodegradable material using sawdust and corn grit held together with cellulose based natural resin. This material can be processed by same machines which are otherwise used for normal plastic.
(9) Environmental polymers of Warrington make biodegradable polymer which can be melt - processed by film blowing or injection moulding etc. Product is water soluble and is useful for interior purpose. It is based on PVOH.
Estimate of current global market for biodegradable plastic is 1.3 billion kg per year. Estimated global market for biodegradable polymers will reach 1.4 billion tons by the year 2000. In response to increasing public concern over environmental hazard caused by plastic, many countries are conducting various solid waste management programmes incl uding plastic waste reduction by development of biodegradable plastic material. There is an intense research for making the biodegradable plastic. Some biodegradable plastic materials under development are -

1. PHAs
2. Polylactides
3. Aliphatic polyesters
4. Polysaccharides
5. Co-polymers and/or blends of above.

Possible Applications of PHAS

Early investigations of PHA granules by electron microscopy after freeze-etching showed that the polymer in the granule underwent a cold drawing process indicating the plastic nature of polyester and suggesting that it can be processed as a conventional thermoplastic. In addition to its potential as plastic material PHA is useful source of stereoregular compounds which can serve as chiral precursors for the chemical synthesis of optical ly active compounds, particularly in synthesis of some drugs or insect pheromones. These substances are biologically active only in the correct stereochemical configeration.

PHAs can be easily depolymerised to a rich source of optically pure bifunctional hydroxy acids. PHB, for example can be readily hydrolysed to R-3-hydroxybutyric acid and is used in the synthesis of Merck's anti-glaucoma drug Truspot. Along with R-1,3-butanediol, it is also used to synthesise-lactams. PHBV received European approval for food contact use in 1996. This opens opportunities in food service and packaging industry. Plant-derived PHAs may in future be depolymerised and used for bulk chemical manufacture. Western Europe, for example produces several million tonnes of butanols , half of which are used directly, or following esterification, as solvents. Besides replacing existing solvents -hydroxy acid esters and related derivatives are likely to find growing use as green solvents similar to lactic acid esters.-hydroxy acids a re more resistant to hydrolysis and are therefore better suited to certain applications. Hydroxy acids may also be converted into crotonic acids, 1,3-butanediol, lactones etc. all of which have existing markets of thousands of tonnes.

PHB,

• is 100% biodegradable,
• can be processed like thermoplastic and
• is 100% water resistant, so that it could be used for similar applications as conventional commodity plastics.

Practical Applications of PHA -

• Packaging films (for food packages), bags, containers, paper coatings.
• Biodegradable carrier for long term dosage of drugs, medicines, insecticides, herbicides, insecticides or fertilizers.
• Disposable items such as razors, utensils, diapers, feminine hygiene products, cosmetics containers, shampoo bottles, cups etc.
• Starting material for chiral compounds.
• Medical applications - Surgical pins, sutures, staples, swabs, wound dressings, bone replacements & plates and blood vessel replacements, Stimulation of bone growth by piezoelectric properties.

Industrial production of PHAs and other biodegradable plastics -

No.	Company	Areas of interest
(1)	Berlin Packaging Corp. (USA)	Marketing
(2)	Bioscience Ltd. (Finland)	Medical applications
(3)	Bio Ventures Alberta Inc. (Canada)	Production in recombinant E.coli
(4)	Metabolix Inc. (USA)	Production in transgenic plants
(5)	Monsanto (USA)
(6)	Polyferm Inc. (Canada)	Production from cheap substrates
(7)	ZENECA Bio-Products (UK) (former ICI, UK)	Production by A.eutrophus
(8)	ZENECA Seeds (UK)	Production in transgenic plants
(9)	Petrochemia Danubia (PCD)	Production using A.lactus

It was shown that PBH-HV, 1 mm molding was completely degraded after 6, 75, 350 weeks in anaerobic sewage, soil & sea water respectively.

Plastic Bag Pollution

Every year, around 500 billion plastic bags are used worldwide. 500,000,000,000. Five hundred followed by nine zeros. That's a lot of bags. So many that over one million bags are being used every minute and they're damaging our environment.


Big numbers can be daunting so let's put it another way. Every man, woman and child on our planet uses 83 plastic bags every year. That's one bag per person every four and half days. Of those 500 billion bags, 100 billion are consumed in the United States alone.

ABSTRACT

Industrial growth, urbanisation, wrong agricultural practices etc. are responsible for pollution and loss of environmental quality. Nature's built-in mechanisms and self regulation ability can not tackle novel pollutants since nature is unfamiliar to it. We will have to remain in tune with the nature and exploit its balancing capacities to ultimately make our environment comfortable. Making ecofriendly products is a part of this process. Bioplastics is one such reality which can help us to overcome the problem of pollution caused by plastics. Bioplastics can be used for manufacture of variety of containers , articles and packaging material which otherwise are produced using non-degradable plastics. There is a lot of research going on to develop bioplastics which can economically replace conventional plastics. This article gives an overview of the fast developing area of bioplastics.