An Examination Of Bioplastics Technology Environmental Sciences Essay

Bioplastics also called organic plastics are a form of plastics produced from renewable biomass sources, such as vegetable oil, corn starch, pea starch or microbiota rather than fossil-fuel plastics which are derived from petroleum. They are polymers which are also obtained from plants genetically engineered to produce them. [1] Some, but not all, bioplastics are designed to biodegrade. Bioplastics are made in order to solve the problems caused by plastics which are non-biodegardable. Bioplastics are not new, it is been there from around 1850.There are different types of bioplastics like the starch based bioplastic, the polylactic acid, PHB, bio-derived polyethylene and the genetically modified bioplastics. Bioplastics are biodegradable that is they can be broken down into simpler compounds by the microbes and thus do not remain for years in the environment. Bioplastics are used in making many items like the disposable cutlery, and for biomedical uses,etc. Its market value is a little less as of now but will increase in the near future.

Global plastics problem

Plastics are carbon-based polymers which are made mostly from petroleum.The word plastic means flexible.Plastics are used to make mostly disposable, low-value items such as food-wrap and product packaging, but there’s nothing particularly disposable about most plastics. On an average, we use plastic bags for 12 minutes before getting rid of them-yet they can take fully 500 years to break down in the environment. [2] Compounds like polyethylene, polypropylene and polystyrene are largely used in the manufacture of plastics. [1] Excessive molecular size is the reason for the resistance of these compounds to biodegradation. Plastics are xenobiotic compounds which are recalcitrant (completely resistant) to biodegradation. [3] Getting rid of plastics is extremely difficult. Burning them can give off toxic chemicals such as dioxins, while collecting and recycling them responsibly is also difficult.With society’s ever-increasing focus on protecting the environment, there’s a new emphasis on designing plastics that will disappear much more quickly. Broadly speaking, so-called “environmentally friendly” plastics fall into three types: bioplastics made from natural materials such as corn starch or generally plants; biodegradable plastics made from traditional petrochemicals, which are engineered to break down more quickly; and eco/recycled plastics, which are simply plastics made from recycled plastic materials rather than raw petrochemicals.

History

Bioplastics are not new. In the 1850s, a British chemist made plastics from cellulose, a derivative of wood pulp. Later, in the early 20th century, Henry Ford experimented soy based plastics in his automobiles, even going to the extent of unveiling a complete prototype plastic car in 1941.But by then petroleum had emerged as a source of synthetic polymers, which possesed more favourable properties than that of plant based plastics. World War II cemented the dominance of synthetic plastics. Only in the last ten years, in response to the rising cost and less supply of oil, have bioplastics re-emerged in consumer applications. In 2003, Nature Works- a joint venture of Cargill, the largest agricultural business in the United States, and Dow Chemical, the country’s biggest chemical company began producing Ingeo bioplastics, which can be extruded into containers for food packaging and into fibers for apparel, furnishings, and disposable products such as baby wipes. Ingeo is a PLA, or polylactic acid, derived from corn. Alternatives are also being made from castor beans, sugarcane, algae and even chicken feathers. Bioplastics are yet to meet the performance requirements of more durable goods. At the moment they are in their infancy. They are actually being used as molded products. Cell phone casings are one such example. The Japanese company NEC unveiled a phone with a corn- based plastic body. applications.

Types of bioplastics:

Starch linked plastics:

Starch is a linear polymer (polysaccaride) made up of repeating glucose units linked by glucosidic linkages in the 1-4 carbon positions. Starch-based biodegradable plastics contain starch contents ranging from 10% to greater than 90%. Starch based polymers can be based on crops such as corn (maize), wheat or potatoes.As the starch content is increased, the polymer become more biodegradable and leave less recalcitrant residues. Often, starch-based polymers are blended with high-performance polymers (e.g. aliphatic polyesters and polyvinyl alcohols) to achieve the necessary performance properties for different applications.

Biodegradation of starch based polymers is a result of enzymatic attack at the glucosidic linkages between the sugar groups leading to a reduction in chain length and the splitting off of sugar units (monosaccharides, disaccharides and oligosaccharides) that are readily utilised in biochemical pathways.

At lower starch contents (less than 60%) the starch particles act as weak links in the plastic matrix and are sites for biological attack. This allows the polymer matrix to disintegrate into small fragments, but not for the entire polymer structure to actually bio-degrade. The bulk of soil bacteria are heterotrophic and utilize readily available source of organic energy from sugars, starch, cellulose and protein.[4] Microbes such as Bacillus, Clostridium, Micrococcus, Aspergillus, Fusarium, Rhizopus; etc are involved in starch hydrolysis.

There are several categories of biodegradable starch-based polymers including:

Thermoplastic starch products;

Starch synthetic aliphatic polyester blends;

Starch PBS/PBSA polyester blends; and

Starch PVOH Blends.

Starch based plastic constitutes about 50 percent of the bioplastics market, thermoplastic starch such as Plastarch material, currently is the most important and widely used bioplastic. Pure starch absorbs humidity and is therefore used for the production of drug capsules in the pharmaceutical industries.

Biolac:

Biolac is polylactic acid. Polylactic acid is an aliphatic polyester. The monomers which make up this polyester are lactic acid units. PLA is a transparent plastic produced from cane sugar, glucose or starch waste. It resembles conventional petrochemical mass plastics in its characteristics, and it can also be processed easily. Polylactic acid can be produced by chemical methods and by fermentation method using microbes.The Lactic acid bacteria (Lactobacillus amylophilus, L. Bavaricus,L. Casei) produce lactic acid using starch, which is then polymerised by bacteria such as A.eutrophus into polylactic acid.[5]Polylactic acid is biodegradable because it is the product formed by bacterial digestion of starch waste. The biodegradation of polylactic acid is brought about by the hydrolysis of the ester bonds by esterolytic enzymes produced by bacteria like Amycolatopsis species.

PLA has become a significant commercial bioplastic. Its used in making bottles, yogurt cups, and candy wrappers. It is also used for making food service ware, lawn and food waste bags, coatings for paper and cardboard and fibers for clothing, carpets, sheets and towels and wall coverings. In biomedical applications it is used for sutures, prosthetic materials and materials for drug delivery. It also has many potential uses, for example as upholstery, disposable garments, awnings, feminine hygeine products and nappies.

Microbially synthesized plastics ( Biopol)

Poly -3 – hydroxy butyrate ( PHB) is a polyester produced by certain bacteria like Rhodovibrio sodomensis in the presence of excess carbon like glucose or starch. It is also called as Biopol.Poly-β hydroxy butyrate accumulates as energy reserve in many micro-organisms like Alcaligenes, Azotobacter, Bacillus, Nocardia, Pseudomonas, Rhizobium etc.It is a poly hydroxy-alkanoate ( PHA). It is a common storage material of prokaryotic cells consisting of a polymer of β- hydroxybutyrate or another β- alkanoic acid. Reserve polymers store excess nutrients present under favourable growth conditions for use during periods of nutrient deprivation.[6] A wide variety of Bacteria and Archaea produce PHAs. Biopol is made in industrial fermentor by bacteria that converts sugars ( refined from corn or beet) into a polymer. Genetically engineered Arabidopsis thaliana a type of cress is also used to make Biopol.[1] Its characteristics are similar to those of petroplastic polypropylene.It produces transparent film at a melting point higher than 130 degrees Celsius, and is biodegradable without residue. PHB is suitable for specialized areas like biomedical use and speciality coatings. A copolymer of PHB ( Poly β- hydroxy butyrate) and PHV ( Poly β- hydroxy valerate) are used in making shampoo bottles in Europe. PHB is easily degraded as it is an energy source of microbes. A copolymer containing approximately equal amounts of PHB and PHV has had the greatest market success thus far.[7]

Bio-derived polyethylene

The basic building block of polyethylene is ethylene. This is just one small chemical step from ethanol, which can be produced by fermentation of agricultural feedstocks such as sugar cane or corn. Bio-derived polyethylene is chemically and physically identical to traditional polyethylene, it does not biodegrade but can be recycled. It can also considerably reduce greenhouse gas emissions. Brazilian chemicals group Braskem claims that using its route from sugar cane ethanol to produce one tonne of polyethylene captures (removes from the environment) 2.5 tonnes of carbon dioxide while the traditional petrochemical route results in emissions of close to 3.5 tonnes. It can be used in packaging such as bottles and tubs

Genetically modified bioplastics

Genetically modified bioplastics are bioplastics which are produced from genetically modified plants and microbes. Normally the plants and microbes produce very small quantities of bioplastics, therefore their production on a large scale is expensive. Genetically modified plants and microbes can be used for the industrial production of bioplastics.

Employing genetic-modification methods Monsanto has also developed plants (oilseed rape) that produce relatively small amounts of Biopol (5% of the total weight) in their cells. The ultimate aim is to develop plants that consist of up to 20% by weight of Biopol, thereby enabling various bioplastics to be produced for a wide variety of applications.

Biodegradation of bioplastics

All bio- and petroleum-based plastics are technically biodegradable, meaning they can be degraded by microbes under suitable conditions. However many degrade at such slow rates as to be considered non-biodegradable. The degree of biodegradation varies with temperature, polymer stability, and available oxygen content. Consequently, most bioplastics will only degrade in the tightly controlled conditions of commercial composting units. An internationally agreed standard, EN13432, defines how quickly and to what extent a plastic must be degraded under commercial composting conditions for it to be called biodegradable. This is published by the International Organisation for Standardization ISO and is recognised in many countries, including all of Europe, Japan and the US. However, it is designed only for the aggressive conditions of commercial composting units. There is no standard applicable to home composting conditions. Biodegradable plastics are made from traditional petrochemicals, which are engineered to break down more quickly. Traditional plastics such as polyethylene are degraded by ultra-violet (UV) light and oxygen. To prevent this process manufacturers add stabilising chemicals. However with the addition of a degradation initiator to the plastic, it is possible to achieve a controlled UV/oxidation disintegration process. This type of plastic may be referred to as degradable plastic or oxy-degradable plastic or photodegradable plastic because the process is not initiated by microbial action. The degraded plastic residue will be attacked by microbes.

Applications

Bioplastics are mainly used in making disposable items such as packaging and catering items such as crockery, cutlery, pots, bowls, straws, etc. The use of bioplastics in making shopping bags is already very common, after this initial use these bags are used for organic wastes and then they can be composted. Bioplastics are also used for making trays and containers for fruits, vegetables, eggs and meat, bottles for soft drinks and dairy products and blister foils for for fruit and vegetables.

Bioplastics are used in making non-disposable items also for example mobile phone casings made by the NEC, carpet fibres by Dupont Sorona and car interiors done by the Mazda company. The French company Arkema, produces a grade of bioplastic called Rilsan, which is used in fuel line and plastic pipe. In these uses the goal is not biodegradability but to create items from sustainable resources.

Drawbacks

Though bioplastics are eco-friendly and are of great use, they have their own drawbacks. When some biodegradable plastics decompose in landfills, methane gas is produced, which is a very powerful greenhouse gas that adds to the problem of global warming. Biodegradable plastics and bioplastics don’t always readily decompose. Some need high temperatures and in some conditions can still take many years to break down. Even then leave behind toxic residues. Bioplastics are made from plants such as corn and maize, so plants which are a food to be eaten are used to make bioplastics which is also an ethical issue.

Some bioplastics are made from genetically modified plants which are harmful to the environment. Bioplastics and biodegradable plastics cannot be recycled easily. There are accelerated rates of deforestation due to the use of plants in making bioplastics. Manufacture of bioplastic materials is reliant on petroleum as a source of energy which is required to power farm machinery, irrigate growing crops, to produce fertilizers and pesticides, to transport crops and crop products to processing plants, to process raw materials and ultimately to produce bioplastics.

Many bioplastics lack the performance and ease of processing of traditional materials. Polylactic acid plastic is being used by a handful of small companies for making water bottles. But the shelf life of these bottles is limited because the plastic is permeable to water – the bottles lose their contents and slowly deform.

Market value of bioplastics

Bioplastics are rapidly catching up. Bioplastics are already unbeatable as medical implants, which dissolve in the body, as compostable mulch films for agriculture. Packaging materials constitute the most important application area for bioplastics, for example filler materials that are utilized in very large amounts. Supermarkets are increasingly using compostable shoppng bags. However the largest growth rates of the use of bioplastics are seen in electronic industries in consoles or cell phone cases. During the past eight years consumption of biodegradable plastics based on starch, sugar and cellulose has increased by around 600 percent. Starch based bioplastics are dominant in Europe.

Bioplastics have the potential to reduce the petroleum consumption for plastics by 15 to 20 percent in 2025.Bioplastics have 10 to 20 percent share of the total plastics market and it will increase to 25 to 30 percent by 2020.There are over 500 bioplastics processing companies already available, more than 5000 is expected by 2020.Europe is one of the leading country in the market of bioplastics. Already bioplastics are used for variety of items, there would be more and more applications for bioplastics in the near future, especially in the automobile and electronics industries where plastics are indispensable. Toyota is one of the leading companies in research and usage of bioplastics. Bioplastic companies are relatively small plants and are in there initial stages of development.

The scenario in India is a little different. The market of bioplastics is a little challenging here due to unawareness about the eco friendly nature of bioplastics and its uses. This therefore can be overcome by creating an wareness on the uses and benefits of bioplastics. The market for bioplastics in India grew at 30 percent in 2008 and will grow at a compound annual growth rate of 44.8 percent between 2009 and 2015.Apart from all this there is an availability of abundant feedstock in due to which it can become a hot destination for bioplastics companies.