Research on Recycling Plastic

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Statistics show that the annual consumption of plastics materials world wide today is approximately 100 million tonnes, from 5 million tonnes in the 1950s. They also show that today, the production of plastics has increased 20 times more compared to that produced 50 tears ago. The many uses of plastics have resulted to their over production, but only a small fraction of the used up plastic materials are recycled. This research paper is aimed at finding out what we can do to save our environment from pollution by plastics.

Increased use of plastics

The increase in the use of plastic materials in all sectors of the economy and in every day life, as well as the reduction in the lifetime of most plastic products have led to a continuous increase in the generation of plastic wastes. Plastics are mostly used in packaging goods. Due to this extensive use of plastics to package goods, most of the plastic waste is found in domestic refuse. There is a relationship between the sector that originates the plastic waste and the life of the plastic products. Plastics used in packaging and agriculture generally have a life time of less than one year, hence in this case, the consumption of waste directly reflects the resin consumed. Plastics used in the manufacture of household items and electrical devices usually have a life time of less than 1 and 10 years, whereas the duration of plastics used in construction, automotive and furniture is typically over 10 years. (Packaging information recycling sheet)

Chart I: Percentage of packaged goods

Source: INCPEN, towards greener households, from

http://www.wasteonline.org.uk/resources/InformationSheets/Packaging_files/image002.gif

Reasons contributing to the poor rates of plastic waste recycling

There are several reasons responsible for the low rates of recycling plastic wastes, compared to other solid materials such as paper or cardboard and glass. A number of problems arise from the large variety of chemical compositions and properties of the different types of plastics, which makes it difficult to establish a general recycling procedure. In addition, plastic wastes are mainly contained in MSW mixed with other solids. Therefore, costly and complex separation treatments must be applied in many cases to obtain a plastic waste stream having a more or less homogeneous composition. Likewise, the low density of most plastics makes it necessary to deal with large volumes of wastes in order to produce a given mass of recycled material.

From an economic point of view, used plastic can be considered as both an important source of valuable chemicals, mainly hydrocarbons, and an energy source. The calorific value of most plastics is similar to that of fuel oils and higher than that of coals. Plastic wastes can therefore be viewed as potential fuels, when other alternatives of valorization are not possible. Plastic waste represents a significant environmental impact due to the following facts:

• Due to their resistance to degradation, plastic materials exist for a long time when disposed off as waste material. Although some biodegradable plastics have been successfully synthesized, most of the commercial resins are not found within this category. The slow degradation of plastic materials is responsible for the progressive reduction of waste material disposal areas. The risk of accidental fires with highly polluting emissions is increased in areas with waste materials containing large amounts of plastics. Plastic material account for approximately 25 % of all solid waste accumulated at any waste material disposal area.
• Plastics usually contain a variety of additives such as fillers, stabilizers, plasticizers, reinforcing agents, colorants etc. Both organic and inorganic compounds are added to plastics to improve and modify their properties, containing in many cases heavy metals. According to the United States Environmental Protection Agency, plastics contribute 28% of all cadmium present in MSW and 2% of all lead.
• As a consequence of their low density, plastics cause a greater visual impact on disposal than many other materials. Similarly, the light weight of plastic cause a greater visual impact on disposal than many other materials. It is also the origin of important limitations on the recycling of plastic wastes, due to increased collection and transportation costs. Thus, to recover one tonne of used plastic it is necessary to collect about 20,000 plastic bottles.
• Since plastic wastes are found in MSW mixed with other solid wastes, complex and costly separation steps are required to produce used plastic streams of relatively high purity.

The Pacific garbage patch

The Great Pacific Garbage Patch is a large mass of marine and plastic debris, floating approximately 1,000 miles west of San Francisco. The waste comprises of plastics that are not biodegradable. The size of the damp has been approximated to be roughly twice the size of Texas and is growing bigger every day. It is approximated to weigh approximately 3.5 million tonnes. The damp is mainly made of trashed items like numerous bottles, toys, shoes, pacifiers, bags and toothbrushes among other items. The damp poses a threat to the marine life, while at the same time posing a danger to human life. The garbage patch arises as circulating currents of the sub tropical gyre naturally tend to agglomerate floating materials in this region. Charles Moore of the Algalita foundation researched on the Pacific garbage patch and found out that approximately100 million tonnes of plastics are produced annually. He says that according to Greenpeace foundation, 10% of the trash ends up in the sea. A study by the United Nations Environmental Program also showed that in the Pacific Ocean, there are approximately 46,000 floating plastic material items for every square mile of the ocean and that the Pacific Garbage was approximately 30 meters deep in 2006. (The Great Pacific Garbage Patch, 2009)

A lot of marine animals and birds have died as a result of plastic indigestion, many of them approximated to be the young ones, who starve to death, as their stomachs are filled with small indigestible items like bottle caps, pacifiers and plastic cigarette lighters. The plastic fragments are a greater danger as they act as absorbers for organic pollutants like PCB’s and DDT` and other oily toxins that cannot dissolve in water. The plastic pellets found in the region are accumulating up to a million times the level of these poisons. These poisoned pellets have entered the food chain of the marine life and soon, it is humans who will be feeding these toxins. Every year, the U.S produces approximately 15 billion pounds of plastics, and of these, only 1 billion are recycled. According to the Los Angeles Times, the plastic usage has been increasing ten times every decade since 1950s. In 2001, the average American used at least 223 pounds of plastic items per year. By 2010, it is approximated that every American will use approximately 326 pounds of plastic. Americans use and discard about 2.5 million plastic bottles every hour, totaling to 22 billion very year. Scientists researching on the matter have said there is no other solution to the problem except to cut down on the use for plastics (The Great Pacific Garbage Patch, 2009).

The scientists have also said that little can be done about the Pacific Patch as it may be impossible to clean up. However, recent developments have shown attempts to clean up the garbage, although this seems almost impossible (Berton Justin, 2007). Even if we stopped using plastics, the patch would still remain for thousands of years, and most of the materials will probably sink to the ocean floor, disrupting the marine ecosystems. To stop the effects that these plastics will have on the environment, marine animals and eventually on human beings, we can stop the production of more plastic materials that are not biodegradable. We can also opt to use proper disposing and recycling methods (The Great Pacific Garbage Patch, 2009).

Management of plastic wastes

There is an immediate need for the government to come up with urgent ways to manage the plastic wastes, and to emphasize on the need to practice the known ways. The general concerns about environmental protection and resource conservation have led to the development of a variety of solid waste management techniques to reduce both the environmental impact of the different types of waste and the depletion of natural resources.  Civilized economies also need to come up with other ways to manage plastic waste which is increasing every day. Management of plastic wastes cannot be treated as an individual problem; it must be considered as an integral part of the global waste management system. Several approaches can be used to manage plastic wastes including:

Reduction

A lot of people are concerned with the number of packaging products for their consumption is packaged in. They avoid buying the products they perceive as over packaged, like the use of standardized boxes to package the goods. In some countries like Korea, products over-packaging is prevented by legislative standards for some types of packaging. For example, the processed goods are only allowed a maximum of up to 15 percent of the volume of the package taken by the empty space, and a minimum of two layers enclosing the product. Minimizing the consumption of raw materials through improvements in the design of products may allow a significant reduction in the amount of wastes generated when they search the end of their life cycle. From 1970 to 1990, there was a decrease in the weight of different food containers. However, it is clear that there is a limit to the advances which can be made by weight reduction, since the mechanical properties and performance of the products are also affected by this decrease.

Table I: Reduction in weight of food containers (1970-1990)

Reusing

Reusing is mainly applied to packaging goods. The best and direct way to reuse the packaging materials is by using them in their original form. It is defined as any operation by which packaging items are refilled or used for the same purpose for which they were conceived, with or without the support of auxiliary products. Packaging products that are meant to be reused should be strong, since they have to withstand the processes of cleaning, transportation and even rough handling. Consumers and industries are encouraged to promote the reuse of goods and packaging instead of disposal. This option can be applied, especially for containers such as bags, bottles etcetera. However, there are some situations where recycling would not lead to any environmental benefits. For example, if the items being reused are very small and light in weight. A life cycle analysis can be used to identify and analyze the environmental impacts of each stage of a product’s life cycle, and hence determine whether reusing will be beneficial.

Recycling

Recycling allows the wastes to be reintroduced into the consumption cycle, generally in secondary applications because in many cases the recycled products are of lower quality than the virgin ones. It must be allowed only when the amount if energy consumed in the recycling process is lower than the energy required for the production of new materials. Plastics can be recycled using two different approaches: mechanical recycling, where the plastics are recycled as polymers, and feed stock recycling, where plastic wastes are transformed into chemicals or fuels. Although it is possible to recycle plastics, the recycling collection facilities for other waste materials are more than those for recycling plastics. For example, in 2001 in the UK, only 23% of the plastic wastes were recycled. This was attributed to high volume to weight ratio of the plastic materials compared to other wastes, making recycling collections of plastic packaging less effective. Therefore, proper waste collecting methods need to be put up, to ensure the plastics are collected properly. Reverse vending machines should therefore be increased to enhance the collection of the plastic wastes.

Energy recovery

When the recycling of wastes is not feasible or there is no market for the recycled product, incineration can be used to generate energy from the waste combustion heat. Plastics are materials of high calorific value; hence plastic waste greatly contributes to the energy produced in the incineration plants. Alternatively, they can be used as fuels in a number of applications: power plants, industrial furnaces, cement kilns etcetera. Incineration of chlorine containing plastics has been the subject of great controversy due to possible formation and release in to the atmosphere of dioxins. However, the relationship between PVC content in the waste stream and dioxin concentration has not been clearly demonstrated. In fact, it seems that the formation of dioxins depends mainly on the incineration conditions rather than on the waste composition.

Mechanical recycling

Mechanical recycling or material recycling of plastics involves a number of treatments and operations: separation of plastics by resin, washing to remove dirt and contaminants, grinding and crushing to reduce the plastic particle size, extraction by heat and reprocessing in to new plastic goods. Because thermo sets can not be re-molded by the effect of heat, this type of recycling is mainly restricted to thermoplastics. Mechanical recycling is limited by the compatibility between the different types of polymers when mixed, as well as by the fact that the presence of small amounts of a given polymer dispersed in a matrix of a second polymer may dramatically change the properties of the latter, hindering its possible use in conventional applications. Thus, the presence of low amounts of PVC in recycled Polyethylene terephthalate (PET) strongly reduces the commercial value of the latter, due to the possible release of hydrochloric acid (HCL) during PET reprocessing. This problem is enhanced by the fact that PVC and PET are difficult to separate from other plastic waste. Another difficulty with mechanical recycling is the presence in plastic wastes products made of the same resin but with difficult colors, which usually impart an undesirable grey color of the recycled plastic.

Feedstock recycling

The severe limitations on the mechanical recycling of plastic wastes highlight the interest and potential of feedstock recycling, also called chemical or tertiary recycling. It is based on the decomposition of polymers by means of heat. Chemical agents and catalysts yield a variety of products ranging from the starting monomers to mixtures of compounds, mainly hydrocarbons, with possible applications as a source of chemical fuels. The products derived from the plastic decomposition exhibit properties and quality similar to those of their counterparts prepared by conventional methods. At present, feedstock recycling is limited by the process economy, rather than the chemical reasons. Three main factors determine the profitability of these alternatives: the degree of separation required in the raw wastes, the value of the products obtained and the capital investment in the processing facilities. In most of the above methods, some pretreatments and separation operations must be carried out on the plastic wastes prior to feedstock recycling, which results to an increase in recycling costs.

Bioplastics

Bioplastics are a new generation of biodegradable and compost-able plastics. They are nontoxic, recyclable and biodegradable and thereby have minimal impact on waste management. We should view them as the solution to the plastic materials problem. Since it would be impossible to reduce the uses of plastic materials, it would be best to use plastics that are biodegradable. This would also reduce accumulation of waste plastics, avoiding situations like the Pacific Garbage Patch.  It would also reduce problems such as land scarcity and eliminate high landfill fees. These are comprised of renewable raw materials like starch, lactic acid, cellulose and soy protein. They are not hazardous, and they decompose in to biomass, carbon dioxide, water etc after being discarded. The growing concern on the environment is responsible for the development of materials from renewable feed-stocks, hence the reemergence of bioplastics. Bioplastics take different time periods for them to decompose, depending on the material from which they are made of. Bioplastics are normally composted in a commercial composting facility, as there are higher temperatures to cause a complete decomposition in a period of 90 to 180 days.

• Compostable plastic

This is a type of plastic capable of undergoing a biological decomposition mostly in a compost pit. Such plastics decompose completely in to water, carbon dioxide and inorganic products so that no thing is seen after decomposition.

• Biodegradable plastic

This is a kind of plastic which disintegrates due to action by micro organisms such as bacteria. It takes different time lengths for decomposition to occur.

• Degradable plastic

These plastics undergo significant changes in their chemical structures under specific environmental conditions which result in the loss of some properties. Such plastics do not necessarily disintegrate as a result of bacterial action.

The rate of biodegradation for different decomposables depends on the composition and thickness of the plastic, and the composting conditions. In commercial composting, the plastics are grind and turned over and over in high temperatures. This shortens the amount of time the materials take to compost and is the method recommended to compost the plastics. When the plastics decompose at home, they take much time depending on the number of times the piles are turned over, the types of plastics being decomposed, and the moisture and temperature availability.

Table I. Estimated Composting Times

Source: http://www.worldcentric.org/biocompostables/bioplastics

History of bioplastics

Bioplastics have existed for a very long time. In the biblical book of Exodus, Noah built his Ark from rushes, pitch and slime, a composite that might today be called a fiber-reinforced bioplastic. Natural resins like amber, shellac and gutta percha have been mentioned throughout the history, including in the Roman times and the Middle Ages. Animal bones (based on protein collagen) and horns and hooves (containing the protein keratin) were sometimes boiled in water or oil, heated directly, or soaked in alkaline solution, then molded or pressed into sheets. Horns were used as early as the thirteenth century to make drinking beakers and other containers. In North America, Native Americans were developing and refining techniques for making horn ladles and spoons long before there was any European contact. The bowl section was thinned, made pliant, then shaped to dimensions wider than the original horn, while the handle retained the natural curvature of the horn’s spiral shape. Molded horn snuff boxes were being manufactured by the eighteenth century. The use of horns continued to be popular throughout the nineteenth century.

Significant commercialization of bioplastics began to be developed in the nineteenth century. By the middle of the century, ebonite- a black vulcanized form of natural rubber- was being processed into items like combs, buttons and electrical insulation. Gutta percha,-like rubber, an extract from tropical trees- was being made into undersea cable insulation, water horses, ornamental frames and other objects.

Future trends in plastic waste management

Today, most plastic and rubber wastes are disposed of in land fills. Future predications show that the significance of other alternatives will have to be enhanced, as the number of landfill sites progressively decreases in many countries. There will have to be an increase in both mechanical and feedstock recycling. At present, the different methods of plastic recycling are limited on a commercial scale by the process economy. The decrease in the price of virgin polymers which has occurred in recent years has negatively affected many recycling programs, because the value of the recycled resins is fixed as a percentage of the virgin polymer price. Fluctuations in the price of virgin resins of 50% or even more within a year are quite usual. The development of recycling process leading to higher quality products would help the recycling economy. In addition, standardization of the recycled resins may be an important factor for promoting their commercial application.

The recycling policy in many countries has been focused in recent years on increasing the recycling rates with little emphasis on the search for applications for the recycled products. A number of measures have been suggested to promote plastic recycling.

• Standards requiring that certain products contain a minimum amount of recycled resin.
• Minimum recycling rates per sector and or material.
• Procurement programs that establish the obligation of purchasing items containing recycled materials.
• Both positive and negative incentives, such as fees imposed on resins that do not meet the minimum standards for recycling or tax credits to business using recycled resins in their products. Likewise, in the case of feedstock recycling, many processes could be economically viable if a credit of a fixed amount was paid for every tonne of plastic waste that is diverted from the landfill to recycling.
• Requirements for manufacturers to maintain responsibility for the final disposal for their products.

Future applications of bioplastics

Growing environmental concern has revived interest in developing materials from renewable feedstock and new bioplastic technologies have began to emerge. In some applications, biodegradability may be the whole point of the product. The biodegradability of agricultural covers is one example. The covers need not be collected and disposed of as do conventional plastic covers. Their biodegradability can play an intrinsic functional role, and the period of use coincides with the period of degradation. Biodegradable agricultural covers also allow the controlled release of active ingredients and can therefore be used to control the soil pests. Another growing importance of the bioplastics could be the use of collection bags for yard, food waste, and other compostable materials. Compostable bags would eliminate the need for bag removal, eliminate the deterioration of the compost from imperfect bag separation, and eliminate the cost of used-bag disposal.

Bioplastics can also be used as root system wrappings. When conventional wrappings, often of burlap or non-degradable plastic, are used to protect plants during shipping and storage on the retail rot, the rot has to be sturdy enough to keep the root ball intact; but if the root system is delicate, as it often is, the wrap can not be so impenetrable as to damage the growing roots. During planting, the wrap either has to be removed or slashed to allow the growing root system to extend beyond the ball size. A biodegradable wrap material, however, has the advantage of degrading over a controlled period of time. It might also have fertilizer additives for the controlled release of nutrients. The biodegradability becomes an intrinsic part of the product application; it becomes a functional requirement as well as an environmental asset.

Another significance of biodegradability and compost ability is beginning to be appreciated through the growing realization worldwide that further increases in agricultural productivity-required for rapid population growth we are experiencing- cannot be take for granted and may become increasingly difficult. The perceive importance of biodegradable compostable materials has been shifting from their waste management value to their role in adjusting agriculture- by increasing crop yield, improving crop quantity, decreasing dependence on chemical fertilizers and pesticides and reducing water requirements. Compostable plastics not only diminish what goes in to landfills; they retain value when they are returned to the farmlands where they began- closing the loop. (Stevens E. S., 2001, pg 128-144)

Conclusion

From the above research, it is clear that there is no way we can do without recycling plastic wastes. Plastic wastes are major and dangerous environmental pollutants, since they do not decompose. Moreover, they make approximately 50% of the domestic wastes. These are clear reasons why we need to recycle them for the sake of the future. If these wastes are not managed and continue to accumulate, they could amount to a global environmental concern in the future. Furthermore, garbage sites, like the Great Pacific Patch will continue to grow bigger. This will lead to increased water pollution, disrupting the marine ecosystems. To avoid such ugly situations, the governments need to increase the campaign against improper damping of plastic materials.