Plastic Bags

Topics: Plastic shopping bag, Polyethylene, Low-density polyethylene Pages: 6 (1942 words) Published: September 4, 2013
One of the most commonly used items in modern generation is the plastic bag. Sufficient, convenient, strong and cheap, plastic bags are seem to be perfect for marketing merchandise, foods, drinks and more. However, there are associated issues with the production, use and disposal of these bags which may not be known to most users but which are nonetheless extremely important especially to the environment. To fully understand the ecological footprint of plastic bags, determining the life cycle of it is needed. This report will outline the ecological footprint of plastic bags by assessing the immediate effects associated with their manufacturing, usage and disposal. Life Cycle of Plastic Bags

I. Manufacturing
Plastics is one of the most abundant materials in this world today. The variety of types and applications are seem to be limitless. PLastic bags are the common use of plastic. However, the production of these bags is destructive to the environment. Extrusion is the process in manufacturing this type of bags. a.1 Energy

The production of PLastics demands large quantities of both energy and raw materials. Two plastic bags require 990 kJ (kilojoules) of natural gas, 240 kJ of petroleum, and 160 kJ of coal (Institute for Lifecycle Environmental Assessment, 1990). Additionally, there are large amounts of energy used to acquire oil, such as the large, fuel-burning heavy machinery, and most of the electricity used in the process of manufacturing the actual bags comes from coal-fired power plants (Greenfeet, 2004). a.2 Raw Materials

The main ingredients in plastic bags are petroleum and natural gas. The manufacturing of plastic bags accounts approximately 4 per cent of the world’s total oil production (Greenfeet, 2004). Components of oil or natural gas are heated which creates hydrocarbon monomers. In the manufacturing process, hydrocarbon monomers are manipulated, resulting in the creation of hydrocarbon polymers (Greenfeet, 2004; Lajeunese, 2004). Different groupings and numbers of monomers make polymers with different properties (Environmental Literacy Council, 2005). a.3 Types of PLastic used

The types of Plastics used in the production of Plastic bags are Polypropylene and polyethylene. BUt the most common used type of plastic for this type of manufacturing is polyethylene,specifically the high-density polyethyleneorsimply knowna s HDPE (Eco-sense, 2002). Polyethylene is a non-renewable resource made from ethylene (Lajeunesse, 2004), which takes hundreds of years to break down (Eco-sense, 2002). Polyethylene is easy and sufficient to use because it can be manipulated into any shape, size, form or color (Greenfeet, 2004). There are two other types of polyethylene, other than HDPE, used to make plastic bags: low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) (Lajeunesse, 2004). LLDPE makes up thicker, glossy bags, such as carrier bags used by businesses in shopping malls, and LDPE is used to make very thin, filmy bags, such as dry-cleaning bags. The main difference between the three types of polyethylene (HDPE, LDPE, and LLDPE) is the branching of the polymer chain of molecules; the more branched out the molecules are, the thinner the plastic (Lajeunesse, 2004). Plastic grocery bags are made of HDPE, which has more branched molecules and consequently lower tensile strength and crystalline form . b.1 Environmental Impacts

b.1.1 Energy
In producing plastic bags, fossil fuels are also needed. Also, since plastic bags are mostly made of the byproduct of natural gas or of oil, if there’s an increase in the production of plastic bags, there is also a high demand in the usage of oil. Hence, the energy used to make one high-density polyethylene (HDPE) plastic bag is 0.48 megajoules (MJ). To give this figure perspective, a car driving one kilometre is the equivalent of manufacturing 8.7 plastic bags (Australian Bureau of Statistics, 2004). There are immense...

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