Introduction
Every product has a lifecycle that defines the impact it creates to the environment from the time of production, usage, and disposal. Life cycle assessment process assists in compiling and examining inputs and outputs of a product regarding materials and energy associated with its functioning throughout the life cycle. Life cycle assessment acts as an essential tool for decision support that helps policy makers and industries assess the cradle-to-grave of a product. The assessment analysis chemical production, material selection, design for environment and environmental impact, industrial ecology, and product lifecycle management (Yorzyk and Radzinski 1). The following paper assesses the life cycle of a car tire using five main stages namely extraction, refining, manufacturing, distribution, and use and disposal concentrating on the quantity on emission.
Life cycles assessment of a car tire
A large number of care tires is currently in use in all parts of the world. For instance, Germany uses about 200 million car tires each time and each year more than 600,000 tons of worn tires are replaced with new ones (Kromer, Kreipe, Reichenbach, & Stark 2). The tire undergoes constant interaction with the environment throughout its service time from the time of acquiring raw materials to the recycling stage. The life cycle assessment of the car tire aims at establishing approaches to reduce negative environmental impacts by quantifying various stages of tire’s life and the amount of toxic gases in form of carbon dioxide they emit to the environment.
Extraction stage
About 7% of all resources needed during the life cycle of a car tire are used during the extraction of raw materials. The car tire is made up of three major components, rubber, steel, and fabric with rubber being the main raw material. Specific materials making up the tire are natural rubber, polyisoprene, polybutadiene, halobutyl rubber, silica, sulfur, zinc oxide, complex organic compounds, textile fabric, and steel. The natural rubber is extracted from major rubber plantations located in rainy tropical areas (Indonesia, Thailand, and Malaysia) (Groover 316). The extraction involves the removal of a milky white secretion tapped from trees. The tapping process takes approximately 20 seconds per tree. Human labor is used to where one person taps approximately 550 trees per day. The secretion is collected on half shell coconuts, or aluminum/plastic cups and collection must occur before coagulation takes place. The labor used for extraction consists mainly of poor people and lowly educated women. These people receive extremely low salaries despite the amount of risks associated with health and wild environment they encounter while extracting rubber. On the other hand, synthetic rubber could be extracted using artificial methods. The extraction stage produces approximately 5.7% emissions.
Refining stage
Refining involves the process of processing the extracted rubber to prepare it for the manufacturing stage. The process involves compounding, mixing, shaping, and vulcanizing. The refining techniques applied for both natural and synthetic rubber are almost similar but uses different chemicals. The extracted rubber is diluted with water to increase concentration and an acid added to coagulate the latex, which takes almost 12 hours. The coagulation appears as soft solid slabs that are squeezed through a series of rolls to get rid of water and reach the thickness of about 3 millimeters (Grooves 318). Heating takes place to bring the rubber to its final form. The heated rubber is more resilient, durable, and has increased utility. The resulting sheet consists of grooves in criss-cross patterns. The sheets are dried for several days to attain the final moisture content. Dried sheets are transported to the manufacturing plant in the form of ribbed smoked sheets folded into large bales. The amount of carbon dioxide emitted to the atmosphere during this stage accounts for about 6% of the total.
Manufacturing
The manufacturing is the most complex and important stage in the car tire life cycle. The tire must strike a balance between comfort, durability, traction, overall cost, and energy efficiency. The manufacturing stage involves both hand-made and automates processes made with a lot of precise to meet demands of different tire applications. The process uses a lot of energy that ends up creating significant environmental impacts. The manufacturing plant consists of machines ran by fossil fuels and gasoline that are major contributors to global warming. The processes rubber is mixed with process oil, pigments, antioxidants, accelerators, and carbon black. Each of these materials contributes the strength, durability, shape, and synthetic value of the tire. A huge blender referred to as the Banbury machine that operates under high pressure and heat mix the materials into homogenized batch black in color. Engineers use computers to conduct the mixing process for consistency. A resulting compounded material moves to the next stage where further processing takes place. The material is processed into treads, sidewalls, and other parts of the tire. Later, the assembly of the tire takes place. Components are arranged in layers starting with the special rubber that forms the inner layer, body plies and belts, strands of steel wire, poly fabric, and a pair of chafer strips (Apollo). A special machine called the tire building machine that consists of a rotating drum shapes the product into the final shape of the tire (Beliczky and Fajen). Finished tires undergo a curing process that uses computer simulations. The manufacturing phase accounts for about 20% of the total carbon dioxide emitted during the tire life cycle.
Distribution
Distribution of the final tire products occurs after the curing process. All tires must undergo a thorough inspection before distribution. The inspection process does not use any environmental resources. In a product life cycle, the distribution stage assumes that high quantities of raw materials are produced near the manufacturing plant, but it is not the case with the car tire life cycle. The car production industry incurs many of transporting the product from the manufacturer to the retailer (Bras and Cobert 37-39). The distribution stage has negligible environmental impacts, but their effects are slightly felt because the emissions produced by vehicles transporting tires from the manufacturer to the retailer accounting for about 0.3%.
Use and disposal
Use phase
The use phase acts as the most significant period in the life cycle of a car tire. The significance of the use stage depends on the amount of fuel consumed by the vehicle based on the distance covered by the tire. The process of converting chemical energy from the fuel to mechanical energy and transmitting it to the tires determines the amount of fuel consumed over specific distance covered helping in establishing tire efficiency. The vehicle uses a small portion of the fuel to drive wheels; hence, should be used in the life cycle analysis. Tires find uses in different sectors. These are transport, consumer, and industrial sectors. The use phase accounts for 75% of total emission.
Disposal
The disposal stage represents the end of life of the product or the grave phase. After use, the car tire is removed and disposed of. The method of disposal used depends on the place where the tire was used and environmental policies of the nation. One of the primary disposal processes for used car tires is in the energy recovery. Used tires act as sources of alternative fuel or substitute for coal in steel plants. The following disposal mechanism is cheap and reduced green gasses emissions. Additionally, tires are disposed and used as construction materials, used in landfill, civil engineering, and for decorations. Additionally, used tires can be re-used in different activities such as slope stabilization, construction bales, erosion control, and protecting coastal and fluvial (Nahar). It accounts for about 2% of overall carbon dioxide consumed.
Summary
The combination of different stages of the product life cycle assessment ‘from cradle to grave' gives an overall picture of its environmental and social impacts. The car tire undergoes a long process from extraction of raw materials to the production of the final product. The energy use in the car tire life cycle is high and creates a lot of impact on the environment (see fig. 1). The manufacturing stage uses the highest amount energy because of many machines and processes involving heat. On the other hand, the extraction process is associated with environmental degradations from cutting tree stems to extract rubber.
Figure 1: The summary of environmental impact of the tire lifecycle in terms of emissions (Source: Nahar 17).
Works cited
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Groover, Mikell P. Fundamentals of Modern Manufacturing: Materials, Processes, and Systems.
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