124

9 Biodegradation of Plastics by Microorganisms

it are suffering from various hazardous plastic wastes, either trapped inside the

plastic frames or by consuming the leftover materials. The easily devourable, small

pieces of plastics lead to malnutrition, obstruction of the small intestines, or slow

intoxication of chemical products leached from plastics. Gases like furans and

dioxins are produced due to burning of plastics and result in ozone layer depletion.

Besides, dioxin adversely affects human health. According to a report published by

the Center for International Environmental Law [3], annual emissions of carbon

dioxide from the production and ignition of plastics will double from 850 Mt./year

by 2030.

The methods which are used to treat plastics have some drawbacks. If plastics are

buried in the soil, it destroys the building holding potential of that soil, rendering

it too soft. In fact, numerous toxic compounds and/or gases resulting from the

incineration of plastics may cause a disturbing contamination of the environment.

The biodegradation of plastics by microorganisms, apart from these processes, has

proved to be an environmentally safe form of reducing and degrading waste plastics.

While recycling and reprocessing is the most preferred process yet, biodegradation

is beneficial and efficient for plastics with defined applications. A variety of

microorganisms have been discovered that are capable of degrading various plastic

materials. Microorganisms are more widespread in nature that may make a signifi-

cant contribution to the biodegradation of plastics. The application of biodegradable

plastics is increasing mainly in the packaging sector, as well as in the agriculture

and health industries. However, biodegradation is not commonly used in plastics

industries. Complex chemical structure of plastics and lack of optimization condi-

tions for plastics degradation may be the causes of less commercial applications. In

order to replace non-biodegradable plastics from different sectors, provision must

be made for a proper and effective waste management system. However, a waste

control procedure, training in waste management, and as well as establishing a suit-

able industrial biodegradation techniques also required. The use of biodegradable

plastics will certainly provide environmental protection accordingly.

9.2

Definition and Classification of Plastics

9.2.1

Definition of Plastic

The word “plastic” refers to the capacity to bend or deform without breaking. The

term “plastic” originated from Greek word “plastikos” and means any material

that may be designed in any manner. It is a kind of synthetic or semi-synthetic

organic polymer with the presence of carbon and hydrogen. It is usually derived

from petrochemicals and can occur in both natural and synthetic forms [4]. This

plastic nature makes the material amenable to be molded, pressed, and extruded

into different forms. These forms included films, threads, sheets, tubes, bottles,

boxes, etc. It is projected that almost 40% of plastics are manufactured for various

packaging purposes in the world. Plastics are light in weight, have good electrical

strength and corrosive resistance, as well as possess excellent electric insulating