Subject Paper No and Title Module No and Title Module Tag Chemistry 4, Environmental Chemistry 16, Soil pollution: Plastics CHE_P4_M16
TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Plastics 3.1. What is plastic pollution? 3.2. Sources of plastic pollution 3.3. Plastics and its environmental hazards 3.4. Effect of plastics on soil 3.5. Prevention and Control 3.6. Waste treatment 4. Summary
1. Learning Outcomes After studying this module, you shall be able to: Know about the plastic and its environmental hazards. Learn about the sources of plastic pollution. Know the use of green chemistry to control plastic pollution. Analyze the preventive methods and waste treatment technologies to manage plastic pollution. 2. Introduction As you already know, pollution has a deadly impact on not just the environment, but also the health of living beings. With several sources of soil pollution, briefly discussed in the previous module, this module mainly focuses on the land or soil pollution and its adverse effects caused by the excessive use of plastics, polythene wastes etc. and their improper disposal. Essentially, the soil fertility deteriorates as the plastic bags get mixed up with manure and remain in the soil for years. 3. Plastics 3.1. What is plastic pollution? Plastic pollution is nothing but collection of several types of man-made plastic materials on land, as well as in water bodies where they create problems for wildlife and their habitats as well as for human populations. Plastic is a synthetic polymer that contains chains of polymers together forming even larger chain of many organic and inorganic compounds, and is mostly derived from petrochemicals like olefins. Plastic materials are mainly classified as Recyclable Plastics (Thermoplastics): PET, HDPE, LDPE, PP, PVC, PS, etc. and Non-Recyclable Plastics such as thermoset and includes Multilayer & Laminated Plastics, Polycarbonate, Melamine, Nylon etc. they are also called as biodegradable and elastomer plastics. Although plastics is considered to be very useful in several
ways, also it is a very useful part of polymer industry, the disposal and production of plastic pose a great threat to all the life forms on Earth. It is estimated that approximately 500-1000 years were taken by a plastic to degrade and this is just estimation, as it is not possible to know the real time for degradation. The manufacturing of plastic results in emission of many hazardous chemical which are harmful for animal and human health. For example ethylene oxide, xylene and benzene are harmful chemicals present in plastic. The other toxic materials present in plastics are phthalates, adipates, and alkylphenols. For manufacturing of OVC pipes, vinyl chloride is used and known to be carcinogen. 3.2. Sources of plastic pollution Plastics as packing material The traditional materials such as paper and cloths have been replaced by plastics. Now-a-days plastics are used for various purposes such as packaging and carry bags as they are cost convenience but this is a wrong choice of material for use. Although plastic bags can be used in multiple purposes but its disposal is a great pollution problem. During the disposal of plastics, it will take a long time to decompose and results in soil pollution. Fig1. Depicts the wide usage of plastic and its relative distribution.
Figure 1: Distribution of plastic usage Computer accessories and other electronic gadgets Plastic waste arising out of the discarded electronic components, electronic toys, batteries etc. (Figure 3), pollute the land and also clog the water bodies like canals, rivers, and lakes, especially in the urban areas. It is estimated that each year approximately 100 million tons of plastics are produced and 25 million tons of which comes under the category of non-degradable plastic. 3.3. Plastics and its environmental hazards Plastics don't Biodegrade Most of the plastic remains in existence for a long time as it is designed to be a long-lived substance that does not biodegrade naturally. There are several forms of plastics having different densities and chemical properties, but they all are similar in one way that if thrown in open, pollutes our land and water. It is possible that the thin plastic bags break slowly and tear into pieces, over time, but these small pieces of plastic remains in the soil and eaten by animals releasing toxins into the animal's system and into our food chain. On the other hand, plastic household items such as plastic containers and bottles cannot be decomposed into small pieces and hence are even more toxic.
Let us discuss about some facts based on plastic pollution: Ø It is estimated that globally around 70000 tonnes of plastic is dumped in the oceans and seas. The plastic materials discarded in seas and oceans, can be eaten by terrestrial as well as aquatic animals and as a result, plastic accumulates inside their bodies. This can cause choking in them, ultimately leading to their death and reduction in aquatic life and aquatic flora and fauna. Ø One plastic drinks bottle can take up to approximately 450 years to decompose in a landfill site. The rural areas are more prone to this type of pollution. Ø Plastic accumulation results in the death of many stray animals due to improper disposal system of plastics. Ø These plastic materials if dumped in landfills can interact with water and results in the formation of hazardous chemicals. If these hazardous chemicals enters the ground level, results in degradation of quality of water and results in groundwater pollution. Ø Many plastic materials cause blockage, which becomes a negative sign as it helps in breeding of mosquitoes which then cause several diseases. Ø Bio-accumulation of plastic inside animals is one of the most recently noticed effects of plastic pollution. From last many years, accumulation of plastics results in the formation of harmful chemicals and cause discomfort to the animals. Even after the death of these animals their body decomposes but the plastic pieces present in their body do not decompose and remain threat to other animals. Ø Toxic chemicals such as Styrene trimer, and bisphenol A affect drinking water quality. Styrene trimer is s by-product of polystyrene. Bisphenol A is known to be a harmful chemical that damages the reproductive system of animals. Ø Usually high velocity winds carried out plastic materials especially plastic polythenes from one place to another. These plastic bags then stuck on fences, trees, towers, buildings, etc. Ø Burning of plastics results in air pollution as it releases toxic chemicals and poisonous gases. Inhalation of these toxic chemicals can cause skin and respiratory problems. 3.4. Effect of plastics on soil Ø The plastics release chemicals in the soil that are toxic and can decrease the fertility of the soil, thereby decreasing the soil yield. Ø When fruits and vegetables are grown on contaminated soil, they also get contaminated and lack in nutrients. Ø Eating this contaminated food can cause poisoning and cause health issues. 3.5. Prevention and Control As we all know there are many materials we use in our daily life made up of plastics. But we should also know about the harm of its excess of use. One cannot out rule the advantages of
plastic but it is better that we take some effective preventive measures to reduce this type of pollution. Ø Plastic Recycling: In order to minimize the environmental pollution caused by plastics it is very important to recycle it. It is a billion dollar industry in developed economies. It can be used for laying down roads in place of bitumen. One can reduce plastic pollution by buying recycled plastic. Ø Prohibition on manufacturing/selling of certain plastic materials/bags: In some countries there is prohibition on manufacturing and use of plastic bags or materials that contains more microns of plastic than are legally prescribed. By this way, control on the increased dependence on plastic commodities can be achieved. Ø Using paper bags and other cloth materials as shopping bags for a customer can be useful. Paper and cloth bags should be used instead of plastic polythenes for shopping and other purposes. Ø Implementing the best civic practices: As the citizens of a community or country the proper disposal of plastic should be ensured: Garbage bins should be used at public places for throwing waste material such as plastic water bottles, containers and other plastic materials. Plastic water bottles, food containers and other plastic material should be dispose in dust bins. One should avoid throwing of plastic and other waste materials in open space. People should be made aware of problems caused by plastics and participate in plastic waste management. People should also help other communities involved in these programs. The main focus of plastic waste management programs is to reducethe use of plastic, reuse it, and then recycle it. Thus, the use of plastics can be controlled and a scientific waste management system instituted for its disposal. 3.6. Waste treatment Future alternative: Eco-friendly plastics: The newer technology entails the use of degradable plastics. It involves incorporation of some chemicals in to the plastic to make it photodegradable/biodegradable or chemically treatable. For example, biodegradable plastics are generally formed by adding starch to normal plastic. When they are subjected to decompose, they are attacked by several bacteria, which results in breaking of these plastic materials into tiny ones. These tiny plastic particles disappear into the soil. When comes to chemically degradable plastics, they can be broken up by spraying a solution on them to dissolve it. Here spray reacts with plastic components and cause them to dissolve. The dissolved plastic is less toxic in nature and can be easily flushed down.
On the other hand if plastics disintegrate on exposure to light they are known as photodegradable plastics. Plastic Waste Management in India In India, plastic disposal is a very serious issue of concern. Several new techniques are employed in order to minimize the effects of plastic pollution on environment. Using incinerators: Incinerators can be used for burning plastic waste. A large amount of plastic wastes can be eliminated by using this method but there are some concerns related with air pollution due to such burning. Although, efforts has been made in order to improve such pollution problems. Utilization of plastic waste in road construction (Polymer Blended Bitumen Roads). Plastic wastes can be used in concentration of flexible roads at various places in India.. Co-processing of Plastic waste in Cement Kiln (Link).Co-processing of plastic waste includes use of waste materials including plastics in processes of manufacturing of cement, lime steel production and power stations. Plasma Pyrolysis Technology (PPT). In this technique of prevention and control method, thermo-chemical property of plastic is integrated. The method is so versatile that it disposes all type of plastic wastes. Thermal disintegration of carbonaceous material in the atmosphere with low concentration of oxygen is known as pyrolysis. This results in the formation methane, carbon monoxide, hydrogen carbon dioxide and water molecules. 5. Summary In this module, you have learnt that Plastic pollution is accumulation of the plastic material on land and in water bodies where they create problems for aquatic flora and fauna. 3R s: Reduce, Reuse and Recycle. The sources of plastic pollution are use of plastic material for packaging and synthesis of electronic devices. The hazards of plastic pollution to air, soil and ground water and also to humans and animals. The plastic waste treatment in India using incinerators, in road construction, in cement kiln and Plasma Pyrolysis Technology.