Environmental Effect on Biodegradability of Plastic and Paper Bags

Abstract

Biodegradation refers to the chemical dissolution of materials by microorganisms or other biological means. Biodegradable materials are those that can be consumed by microorganisms whereas biodegradability of a material refers to the ability of that material to be decomposed by biological agents, especially bacteria. Plastics are synthetic or semi - synthetic long chain polymeric molecules that are moldable. They are made from inorganic and organic raw materials, such as carbon, silicon, hydrogen, nitrogen, oxygen and chloride. The basic materials used for making plastics are extracted from oil, coal and natural gas. Plastics are biodegraded aerobically in wild nature, anaerobically in sediments and landfills and partly aerobically and partly anaerobically in composts and soil. Carbon dioxide and water are produced during aerobic biodegradation and carbon-dioxide, water and methane are produced during anaerobic biodegradation. Polythene & plastic has become a part of modern day living right from packaging to making toys and various other applications. The environmental effect on the biodegradability of polythene bags (yellow nylon and black nylon), newspaper and brown paper were assayed by exposing the materials to different environmental conditions such as direct sunlight, fresh water, salt water obtained from the ocean leaf pile and soil. The bacteria present on the materials were identified and their colony counts performed at the start of the study and after three months. Physicochemical parameters were also analysed. Bacteria isolated from the biodegrading materials include; Pseudomonas aeroginosa, Proteus vulgaris and Enterobacter aerogenes, Staphylococcus aureus and Bacillus subtilis, while the fungi isolated include Penicillum chrysogenum, Aspergillus niger,, Aspergillus flavus, Rhizopus stolonifer and Neurospora sitophila. The bacteria were organised into biofilms. There was in an increase in the bacterial and fungal colony counts after three months indicating their involvement in the biodegradation of the materials studied. This study has shown that paper bags are more liable to degrade faster than plastic bags and that environmental factors like salt water which represents the sea condition and sun has more effect on the biodegradability process of the suspended materials. It is therefore recommended to use more of paper bags for shopping and packaging of goods.