Design Life-Cycle

Toan Le

Professor Christina Cogdell 

DES 40A

November 28, 2021

Raw Materials of Cleats

How complicated a small thing could be, in terms of the combination of materials that are needed to entirely form it? With the rate of overusing materials and resources to the warning level, that is the question we should ask ourselves every day as a practice system whenever we have a chance to observe an object-related topic. For example, sport is a big part of many people’s lives, especially in the United States where opportunities are everywhere for people from a young age, and to the people that are not fans, they still at least have some chances to interact with sports in their lifetime. To apply the above question on the sports field, have you ever wondered what materials that the shoes of the sports players, who we usually see on television, were made of, especially soccer or football players? Besides not being normal shoes, which is obviously not the same as our daily shoes due to the rate of movement and usage of players, there is a part that not anyone knows about, the cleats. People usually called shoes with cleats simply as cleats, athletic shoes, or cleat shoes. Like any other shoes, the combination of materials that are used to make cleats is unbelievable to people who have never known, even a minor part of a shoe takes a good amount of effort and resources to make. The production of cleats would show how complicated the process of producing goods is, together with the involvement of raw materials, in different use and conditions, continuously take part in cleats’ life cycle.

Instead of starting with the original primary raw materials of the whole process, the role of secondary materials which are made from those originals, and later become the primary materials of the manufacturing process should be mentioned first as the basic layer for this research paper, and it would also briefly go through the original primary raw materials. The raw materials should first be categorized based on each part of the cleat shoes, which are the shoelaces, the general shoe body, the insole, the midsole, and the cleats themselves. beginning with the shoelaces, which are made from synthetic fibers such as nylon, textured polyester, spun polyester, polypropylene, and/or other traditional materials (“Shoelaces Manufacturing”). All three of them, nylon, polyester, and polypropylene are synthetic polymer materials that are made of the process of chemical reaction of crude oil, or petroleum, gas, and water. However, different from nylon and polyester, polypropylene is “a nonwoven textile, which means that it is made directly from a material without any need for spinning or weaving” (Sewport), yet both polyester and nylon need a process of weaving or spinning in order to make them into the fabric. For Nylon, the process would be breaking a nylon sheet into small pieces, melting and weaving with a spinneret to individual fibers, which later on will be woven into the fabric (Uren). For polyester, the process of producing polyester fabric would be melting polyester plastic pellets “and extruded through tiny holes called spinnerets to form long threads, which are then cooled to harden into a fiber” (CFDA), later the fibers would be put under a process of twisting and spinning under heat-treating twister to form a textured polyester yarn (US3886722A). Even a small part like that already needs a complicated process of combining and extracting material to obtain.

Moving on to the next part is the majority of the shoes, including from the heel to the upper area and the tongue, which is made mainly from leather or synthetic fibers with the structure like the shoelaces (“Soccer Cleat Materials”). Leather is an animal-based fabric, which is obtained through the skin of animals, the most common type of leather that still exists in the market is Kangaroo leather, and like its name, it is made from kangaroo skin after humans hunted them down and skinned them. Leather-type fabric in cleat production is believed to be durable, lightweight, and high quality, yet also because of the hardship of producing them, leather cleats are more expensive to compare with synthetic fabric (“Soccer Cleat Materials”). Not only the price that affects the common use of leather and synthetic fabric, the difference in use, durability, pliability, and regularity of usage also affect the choice of customers and businesses toward the type of materials. Besides that, with nowadays ethical standards, using animal-based material would raise up a big argument about humaneness and civilization in the society, so leather, prior to its relation with social conflicts, is still a big question mark of whether or not we should still keep it in the process. 

The next part of the shoes is the insole. Generally, the insoles of shoes would be made of gel, or foam, or even cork, yet we are talking about athletic cleats, and cork is too hard for comfortable movement, there is only gel and foam as the suitable material for insoles. In fact, the main material for the foam insole is called viscoelastic foam, and with or without the gel material. Viscoelastic foam is a memory foam that reacts with the change of movement and slowly moves back to its original form, based on what Teodor Socaciu wrote in his research, “memory foam cells compress fully when pressed upon by another force, then they spring back to their original shape very slowly, (hence the name memory foam- The foam appears to remember the shape of the last object placed upon its surface)” (Socaciu). According to Wade Motawi in his book named Shoes Material Design Guide, viscoelastic foam consists mainly of polyurethane and other chemicals, which react with the heat of the human body (Motawi 60). And, like the plastic-based materials such as nylon and polyester, the production of polyurethane is also strongly dependent on the petroleum industry, for due to the research about Polyurethane from Ohio State University, its “ two major raw materials (polyols and isocyanates) are largely petroleum-derived” (Li).

The last part of the cleats shoes is the combination of the midsole and the cleats themselves, for the cleats are mostly attached to the midsole as a whole. The midsoles of cleats are primarily made of EVA foam, short for ethyl vinyl acetate. Ethyl vinyl acetate is the copolymer material between ethylene and vinyl acetate (Verdejo). Based on the patent of the invention of Yoshiharu Nagao, ethyl vinyl acetate is created from the reaction of heating and cooling between ethylene and vinyl acetate (Nagao). Ethylene, or ethene, is obtained through the steaming cracking reaction of natural gases such as propane and methane by heating (“Ethene (Ethylene)”), and vinyl acetate is made from the interaction between ethene, oxygen, and acetate acid in a palladium catalyst (“An Introduction to Vinyl Acetate-Based Polymers”). The second part of the combination and last part of the shoe, which is also the main character of the research, cleats. There are two types of cleats, metal cleats and molded cleats. Metal cleats, as clear as their name, are made of metal, specifically steel, which is the result of the interaction between iron and carbon. Molded cleats, however, are made of either rubber, a material that is produced by using liquid sap, or latex, obtained from Hevea brasiliensis trees (“How Is Rubber Made”), or normal plastic, which is mostly polymers material based. And, that is the whole list of materials that are used in the process of making shoes; However, it is not the end of the story, for the involvement of materials would continue throughout the life cycle of the cleats.  

The life cycle of a product includes six steps, which are (1) raw materials acquisition, (2) manufacturing, processing, and formulation, (3) transportation and distribution, (4) use/reuse and maintenance, (5) recycle, and (6) waste management. The main portion of the research above already covered the first two steps of the process, which are raw materials acquisition and manufacturing, processing, and formulation. The three steps of transportation and distribution, use/reuse, and maintenance, together with recycling are pretty similar in terms of the involvement of materials. The main similarity in those steps is the involvement of paper, which would be used for packaging the cleats in transportation and distribution, and later on would be the material for delivering for the use of customers, or shipment for maintenance, and lastly, in the recycling process, the paper would be the raw material for anything in the recycling process, for papers that are used to distributing products are mostly recyclable. The cleats themselves are also the “raw material” for those three steps of the life cycle, acting as raw material for transporting, distributing, using, and also recycling. However, there are also differences between the steps, for example, when transporting the product, there would be the use of oil, or gasoline for transporting vehicles on the ground, sky, or marine routes. The last step, waste management, however, is the most important step that we need to be more considerate about for the better world of the next generations. The choice of raw materials for the waste managing step would also affect the method of waste disposal. There are various ways for waste management, such as recycling each part of cleats into new shoes, melting down the old plastic for new products, choosing recyclable materials to produce cleats so we can stop overproduction. However, the raw material should be put into the waste management step of cleats’ life cycle is the carbon waste from crude oil or petroleum. The industrial waste is known as carbon dioxide, and due to Zoe Cormier from BBCEarth, using chemical tricks to turn carbon dioxide from industrial waste into the raw materials of the production of the polymers would “Not only reduce the amount of fossil fuels we use, it would have an impact on climate change, lowering greenhouse gas emissions.” (Cormier). The use of waste in the new production would be a big change for the environment and a big help for the next generation on dealing with pollution.

Even cleat shoes for athletic players require a complicated process to produce, and throughout the life cycle of it, the materials that involve keep moving around, and changing for each step. On a daily basis, we hardly ever thought about the waste, usage, and consequences of materials that were put into production. The world is not a place for us to be carefree anymore, for pollution, waste, and social conflicts from overusing materials have become our everyday issues. In order to maintain a better life for ourselves, and maybe for our descendants, we should stop neglecting the Earth and take action in being more considerate.

Bibliography

“An Introduction to Vinyl Acetate-Based Polymers.” Mallard Creek Polymers, https://www.mcpolymers.com/library/vinyl-acetate-based-polymers#:~:text=Vinyl%20acetate%20is%20prepared%20from,acid%20over%20a%20palladium%20catalyst.&text=The%20basic%20chemical%20reaction%20is%20shown%20below%2C%20along%20with%20the,used%20in%20its%20pure%20form. 

Cormier, Zoe. “Turning Carbon Emissions into Plastic.” BBC Earth, https://www.bbcearth.com/news/turning-carbon-emissions-into-plastic.  

“Ethene (Ethylene).” Ethene (Ethylene), 4 Jan. 2017, Accessed 29 Nov 2021 https://www.essentialchemicalindustry.org/chemicals/ethene.html. 

“How Is Rubber Made?” Coruba, 16 Oct. 2020, Accessed 29 Nov 2021, https://www.coruba.co.uk/blog/how-is-rubber-made/. 

Li, Yebo, and Randall Reeder. “Turning Crude Glycerin into Polyurethane Foam and Biopolyols.” Ohioline, 6 Sept. 2011, https://ohioline.osu.edu/factsheet/AEX-654-11.  

Nagao, Yoshiharu. “US6646087B2 - Method of Manufacturing Ethylene-Vinyl Acetate Copolymer.” Google Patents, Google, https://patents.google.com/patent/US6646087B2/en.  

Motawi, Wade. Shoe Material Design Guide. Wade Motawi, 2018. 

“Polyester.” CFDA, Accessed 29 Nov 2021, https://cfda.com/resources/materials/detail/polyester#:~:text=To%20make%20polyester%20fibers%2C%20PET,create%20fibers%20with%20different%20qualities. 

Sewport. “What Is Polypropylene Fabric: Properties, How Its Made and Where.” Sewport, Sewport, 28 Feb. 2019, https://sewport.com/fabrics-directory/polypropylene-fabric. 

“Shoelace Manufacturing.” Shoelaces Express, 2021. Accessed 29 Nov 2021 https://shoelacesexpress.com/pages/shoelace-manufacturing.    

Socaciu, Teodor., et al. “Research and Application of Visco-elastic Memory Foam, In The Field of Footwear Manufacturing”. Researchgate.net. 2010 https://www.researchgate.net/profile/Teodor-Socaciu/publication/228544358_Research_and_Application_of_Visco-Elastic_Memory_Foam_in_the_Field_of_Footwear_Manufacturing/links/54be5f610cf218da9391e7fd/Research-and-Application-of-Visco-Elastic-Memory-Foam-in-the-Field-of-Footwear-Manufacturing.pdf 

“Soccer Cleat Materials: Buying Guide.” Optcool.com, Accessed 29 Nov 2021, https://optcool.com/pages/soccer-cleat-materials. 

Uren, Ashlee. “Material Guide: How Sustainable Is Nylon?” Good On You, 16 June 2021, https://goodonyou.eco/material-guide-nylon/.  

“US3886722A - Process for Producing Polyester Textured Yarn.” Google Patents, Google, 3 June 1975, https://patents.google.com/patent/US3886722.   

Verdejo, Raquel, and Nigel Mills. Performance of Eva Foam in Running Shoes - Researchgate.net. 2002, https://www.researchgate.net/profile/Raquel-Verdejo/publication/225030841_Performance_of_EVA_foam_in_running_shoes/links/0912f50a49a7ccecd8000000/Performance-of-EVA-foam-in-running-shoes.pdf.

Maria Sanchez

Professor Christina Cogdell

DES 40A

2 December 2021

Athletic Cleats: Embodied Energy of Their Life Cycle

Athletic shoes are an essential need for athletes nationwide. Emerging athletes for baseball, soccer, and other sports are constantly upgrading their cleats from their intensive wear; thus, creating a high demand for their production, which means an increased use of energy. The embodied energy for the life cycle of athletic cleats includes the acquisition of materials for their outer and inner counterparts, the manufacturing of the shoe itself, and the management of the shoe post utilization. 

Shoelaces hold a shoe securely and in order to do so, the material of the shoelaces are required to uphold tension. Although there are naturally made fibers, synthetic fibers hold up stronger and are more resistant, but the manufacturing process of those synthetic fibers requires the acquisition of petroleum [1]. In order to do so, oil drilling is involved which takes up manpower and roughly sixteen terra-watts (electrical energy) per year from oil companies [2]. In addition to drilling, the processing of manufacturing petrochemicals is also involved. According to Energy Efficiency Improvement and Cost Saving Opportunities for the Petrochemical Industry - An ENERGY STAR(R) Guide for Energy and Plant Managers, “The petrochemical industry is responsible for 70% of the chemical industry’s expenditures on fuels and 40% of the expenditures on electricity. The costs of energy and raw materials (which are to a very large extent derived from fossil fuels) are roughly 2/3rd of the total value of shipments of the petrochemical industry” [3]. 

Included in these fibers is the production of Nylon. The nylon process is broken down into three components: prepolycon- densation, melt polycondensation, and  the solid-state stage [4]. Both heat and pressure are involved in the production of nylon that is made from petroleum (it is a synthetic fiber) and/or carbon. The presence  of  water  and  higher pressure, with the inclusion of atmospheric pressure, in the first stage produces the vaporization of HMDA and dehydration of adipic acid [4]. Once the polymerization takes place, the sheets produced are broken down. More energy is used to melt down the pieces and then to put them through spinnerets to create the nylon fiber before they are spun into threads [5]. In total, for every 2.2 pounds of fiber produced to make nylon, around 250 megajoules of energy are used [5]. However, it takes twice as much energy to produce polyester. 

The material terephthalate is introduced to ethylene glycol at around 302-400 degrees Fahrenheit (polymerization) [Figure 1]; then more energy is used for drying, melt spinning (also uses heat at 500 degrees Fahrenheit), drawing the fiber, and winding the material [6, Figure 2]. Polypropylene is the last component for the manufacturing process of the shoelaces. In addition to the production of polyester, polypropylene is also manufactured using high amounts of energy. Aside from the utilization of oil like the previous fibers mentioned, the production of polypropylene also uses other energies, such as steam, electricity and natural gas [Figure 3]. Their totalled energy in the production process is 67.7,  21.0  and  11.3%, respectively [7].

Rubber is the common material used for the outsoles of cleats and shoes in general. Its oil and water resistance qualities make an ideal material for shoes, in addition to the withstanding of high heats, rough terrains, and slippery surfaces [8]. Rubber is acquired in its natural form latex, which is harvested (human power) in a sap-like quality in trees before it is transported and manufactured into its hard form (then referred to as rubber) [9]. It is estimated that each rubber industry consumes about 5640 MW h of energy annually because of the pumps, heaters, cooling systems and lighting involved [10]. This, of course, does not include the manpower required which estimates about 68,000 workers in the industry [10]. Figure 4 demonstrates a breakdown of the percentages for each individual component of energy used for the production of rubber.

Leather is the main material used for the insoles of cleats. It is strong, comfortable and the material itself breathes [11]. Of course, the mechanical energy involved begins from the upbringing of the animal up to the slaughtering. It is estimated that 159 million animals are killed for the leather industry [12]. From there, the skin is salted, tanned, and dyed. From the previously described materials, it should be known that both chemical and manual energy goes into treating the skin and then processing it. 

For the midsoles, Ethylene Vinyl Acetate (EVA) is used for its durability. EVA is a chemical mixture of pressurized ethylene gas and catalysts bound together at high temperatures (100-300 degrees Celsius) and high pressures (1300-3500 bar)[13]. With it, is the production of plastic that is part of the studs for the shoe. Crude oil, natural gas and coal are extracted for its manufacturing, which also includes chemical energy [14].

As most companies do, the manufacturing of athletic cleats include the assembly line that puts all the different parts together. In this case, machinery and human power is used. The first step is springing the pattern before it is cut, and sent to the stitching line where the outer soles and shell of the shoe is put together. A single stitching department has about 50-100 workers using machines (electricity and power) which emphasizes the amount of electrical and mechanical energy from the people putting in the shoe as well as putting the pieces together in its early stages [15]. A different department called the assembly line is where the upper part of the shoe is connected with the sole by cementing them together, or sewing them together depending on the company [15]. The shoe is inspected, cleaned and packaged, which requires human power as previously mentioned. The transportation of both materials and finalized products use petroleum and as stated earlier, uses up chemical and mechanical energy [2]. Figure 5 demonstrates the general process described.

Once the athletic shoes are in-stores, athletes are able to pick and wear from a variety of styles. Mechanical energy is used in this instance again, more so than the average energy that a person uses up because of the intensive and extensive use of the shoes that derive from the long hours of training and playing. It is safe to assume that most athletes use multiple pairs of cleats, breaking each pair in almost immediately and just as quickly using them up. Unfortunately, athletic shoes have a shorter usage because of the constant and intensive mechanical wear, making it difficult to upkeep. Post utilization, 80% of the shoes are landfilled; it is noted that most of the energy used happens during the material processing and manufacturing stage [16]. However, some facilities work to mechanically separate the fabrics, plastics, metals, and fibers before sending them to respectively recycle places for each material.  

The life cycle of an athletic cleat embodies energy beyond its production phase. Different types of energy make up its pre-production, production, and waste management. Considering their brief usage span and high production demand, new methods of material acquisition should be set in place to save the extensive amounts of chemical and electrical energy used to manufacture the shoe. This way, athletes could enjoy sports in comfortable athletic cleats, and the environment would have reduced energy consumption.

Footnotes

1. Team, Vedantu Content. “Synthetic Fibers Are Obtained by:A. Chemical Processing of PetrochemicalsB. Chemical Processing of Natural FibersC. Manual Processing of Natural FIBERSD. Both A and B.” Synthetic Fibers Are Obtained by A Chemical Processing Class 10 Chemistry CBSE, 16 Dec. 2020, link

2. Forbes-Cable, Malcolm. “Oil and Gas Companies Can Power Offshore Platforms with Renewables.” Greentech Media, Greentech Media, 21 Nov. 2019, link

3. Neelis, Maarten. “Energy Efficiency Improvement and Cost Saving Opportunities for the Petrochemical Industry - an Energy Star(r) Guide for Energy and Plant Managers.” Energy Efficiency Improvement and Cost Saving Opportunities for the Petrochemical Industry - An ENERGY STAR(R) Guide for Energy and Plant Managers (Technical Report) | OSTI.GOV, 1 Sept. 2008, link

4. Yao, Zhen, and W. Harmon Ray. “Modeling and Analysis of New Processes for Polyester and Nylon Production.” AIChE Journal, vol. 47, no. 2, 2001, pp. 401–412., link

5. Camille, “Camille.” Natural Clothing, 27 Feb. 2019, link

6. “Polyester.” How Products Are Made, link

7. Harding, K.G., et al. “Environmental Analysis of Plastic Production Processes: Comparing Petroleum-Based Polypropylene and Polyethylene with Biologically-Based Poly-β-Hydroxybutyric Acid Using Life Cycle Analysis.” Journal of Biotechnology, Elsevier, 25 Feb. 2007, link

8. “The Advantages of Rubber Soles.” Kaliber Footwear, 25 Aug. 2020, link

9. Company, Stern Rubber. “From a Gooey Sap to a Rubber Band.” Stern Rubber Company - Est. 1969, link

10. R. Saidura, S. Mekhilefb, Author links open overlay, et al. “Energy Use, Energy Savings and Emission Analysis in the Malaysian Rubber Producing Industries.” Applied Energy, Elsevier, 22 Jan. 2010, link

11. “Why Leather?” MAHI Leather, link

12. Milkowski, Eva-Maria. “LDPE & Eva Production.” Cerobear, Cerobear, 18 June 2021, link

13. Bpf. “British Plastics Federation.” How Is Plastic Made? - British Plastic Federation, link

14. “How Does a Factory Make Shoes?” How Shoes Are Made: The Sneaker Factory, 20 July 2020, link

15. Lynette Cheaha Natalia Duque Cicerib Elsa Olivettic Seiko Matsumurad Dai Forterree Richard Rothf Randolph Kirchaing. “Manufacturing-Focused Emissions Reductions in Footwear Production.” Journal of Cleaner Production, Elsevier, 12 Dec. 2012, link

16. Cheah, Lynette. “Manufacturing-Focused Emissions Reductions in Footwear Production.” Journal of Cleaner Production, Elsevier, 12 Dec. 2012, link

Bibliography

1. Lynette Cheaha Natalia Duque Cicerib Elsa Olivettic Seiko Matsumurad Dai Forterree Richard Rothf Randolph Kirchaing. “Manufacturing-Focused Emissions Reductions in Footwear Production.” Journal of Cleaner Production, Elsevier, 12 Dec. 2012, link

2. Bpf. “British Plastics Federation.” How Is Plastic Made? - British Plastic Federation, link

3. Camille. “Camille.” Natural Clothing, 27 Feb. 2019, link

4. Cheah, Lynette, et al. “Manufacturing-Focused Emissions Reductions in Footwear Production.” Journal of Cleaner Production, Elsevier, 12 Dec. 2012, link

5. Company, Stern Rubber. “From a Gooey Sap to a Rubber Band.” Stern Rubber Company - Est. 1969, link

6. Forbes-Cable, Malcolm. “Oil and Gas Companies Can Power Offshore Platforms with Renewables.” Greentech Media, Greentech Media, 21 Nov. 2019, link

7. Harding, K.G. “Environmental Analysis of Plastic Production Processes: Comparing Petroleum-Based Polypropylene and Polyethylene with Biologically-Based Poly-β-Hydroxybutyric Acid Using Life Cycle Analysis.” Journal of Biotechnology, Elsevier, 25 Feb. 2007, link

8. Kuo-Wen Chen, Lung-Chieh Lin, Wen-Shing Lee, “Analyzing the Carbon Footprint of the Finished Bovine Leather: A Case Study of Aniline Leather” Energy Procedia, Volume 61, 2014, Pages 1063-1066, ISSN 1876-6102 link

9. Milkowski, Eva-Maria. “LDPE & Eva Production.” Cerobear, Cerobear, 18 June 2021, link

10. Neelis, Maarten. “Energy Efficiency Improvement and Cost Saving Opportunities for the Petrochemical Industry - an Energy Star(r) Guide for Energy and Plant Managers.” Energy Efficiency Improvement and Cost Saving Opportunities for the Petrochemical Industry - An ENERGY STAR(R) Guide for Energy and Plant Managers (Technical Report) | OSTI.GOV, 1 Sept. 2008, link

11. R. Saidura, S. Mekhilefb. “Energy Use, Energy Savings and Emission Analysis in the Malaysian Rubber Producing Industries.” Applied Energy, Elsevier, 22 Jan. 2010, link

12. Team, Vedantu Content. “Synthetic Fibers Are Obtained by:A. Chemical Processing of PetrochemicalsB. Chemical Processing of Natural FibersC. Manual Processing of Natural FIBERSD. Both A and B.” Synthetic Fibers Are Obtained by A Chemical Processing Class 10 Chemistry CBSE, 16 Dec. 2020, link

13. Yao, Zhen, and W. Harmon Ray. “Modeling and Analysis of New Processes for Polyester and Nylon Production.” AIChE Journal, vol. 47, no. 2, 2001, pp. 401–412., link

14. “How Does a Factory Make Shoes?” How Shoes Are Made: The Sneaker Factory, 20 July 2020, link

15. “Polyester.” How Products Are Made, link

16. “The Advantages of Rubber Soles.” Kaliber Footwear, 25 Aug. 2020, link

17. “Why Leather?” MAHI Leather, link

Ziming Zhong

DES 40A

Professor Cogdell

Waste of Cleats on Shoes

Introduction

         Cleats or studs are the external attachments and protrusions found on the soles of shoes, especially sporting shoes. The cleats are primarily used to provide extra traction vital in soft or slippery surfaces (Heidt et al., p. 834). The extra traction is made possible because of the conical or blade-like shape that the cleats possess. In this regard, their traction proves useful to athletes who utilize the boots using sporting activities. Many cleats are made of plastic, rubber, or metal, and the shoe is worn depending on the prevailing environment of play, such as grass, ice, or artificial turf grounds. The strong ground grip provided by the cleats ensures that the player effectively and easily makes rapid directional changes without toppling over. However, when the cleats get depleted or detached from the shoes, they become waste products. Most cleats are made from plastic, metal, or rubber, and such materials are not biodegradable, posing a hazardous environmental risk (Yehia, p. 1). The paper will discuss waste of cleats in the steps provided in the product life cycle articulating raw materials acquisition, manufacturing, processing, formulation, distribution and transportation, use, re-use, and maintenance, recycle and waste management.

Raw Materials Acquisition

         The raw material acquisition part of the lifecycle entails getting the stuff needed to make the material or product. Cleat materials are mostly made from metal, rubber, or plastic. However, rubber and plastic and the most common materials after metal cleats were disputed by authorities because they could cause injury to players when their body parts crash with the cleats (Agrawal et al., p. 257). The materials serve as waste products when not disposed of correctly. The outsoles are made of rubber, insoles of leather, cork, gel, and foam (Chertow & Jooyoung, p. 5). The midsole is made of ethyl vinyl acetate, while the inside of the cleat is from foam.

When extracting rubber products, various toxic byproducts affect the extractors. For instance, extracting synthetic rubber utilizes harmful chemicals like sulfur, stearic acid, and zinc oxide that pose threats to the health safety of the extractors. O’Malley et al., (p. 512) point out that rubber’s commercial and bulk production produces phenolic and catecholic chemicals that make the extractors vulnerable to occupational vitiligo. The condition is characterized by a cutaneous depigmentation of the patchy loss of skin pigmentation. Other effects are seen in causing serious and fatal injuries brought forth by calenders, internal mixers, and roll-mills, with many accidents occurring when clearing or repairing the blockages. When making plastic cleats, ethyl vinyl acetate is utilized as a polymer. Although the Food and Drug Administration (FDA) observes that it is not a dangerous material when used in food transportation, packaging or production, high exposures to ethyl acetate irritates the throat, nose, eyes and skin, with some fatal cases making extractors pass out or feel dizzy and lightheaded (Yaqub et al., p. 2).            

Manufacturing, Processing, and Formulation

The manufacturing, processing, and formulation part involves making the material or product. Apart from rubber cleats, another common cleat material is leather. Manufacturing begins by laying out the strips of synthetic or real leather and the cleat uppers marked to provide an easy outline for cutting (Brandt et al., p. 428). Later, the material undergoes printing and stitching, where decorative details are accounted for before the cleats are assembled and packaged.

When manufacturing rubber cleats, the factory conditions regarding water and air quality inside and next the factory are not appealing. Most leather products are sourced from animal skin, meaning there are bad odors before the skin is completely dried. Similarly, washing the skin makes the water unsafe for drinking, although it can be poured out in the fields to enhance fertility. However, manufacturing, processing, and formulation articulate biological substances, fumes, vapors, particulates, and gases (Kolomaznik et al., p. 514). According to the Centres for Disease Control and Prevention, rubber processing contaminates the work environment with fumes, vapors, gases, dusts and chemical by-products like Nitrosamines. Such products are absorbed in the body through the skin or inhalation. The workers are exposed to physical hazards of lifting, repetitive motion and noise.

Distribution and Transportation

The distribution and transportation bit entails getting the material or product to the stores and consumers. After the cleats are assembled and packaged, they are transported via roads, air, or sea and distributed to retailers, supermarkets, or cleat markets like football, rugby, soccer, and cricket (Hennig & Thorsten, p. 186). When transporting the cleat products employing cars, planes, ships, rail, and trucks, various emissions such as carbon dioxide cause air pollution leading to greenhouse effects. Means of transport via roads like buses, trucks, and cars use fossil fuels such as petrol and diesel, which primarily contribute to environmental pollution. Vehicle exhausts emit air toxins like nitrogen oxides which are harmful to the environment.   

Use, Re-Use, and Maintenance

Use, re-use, and maintenance entails what happens when the material or product is in the hands of consumers. In this essence, the player or customer has the shoe or boot with cleats attached. Cleat maintenance is an excellent strategy that allows durability and makes them look better for a long time. Since most shoes with cleats are used in sporting activities, they are often wet and dirty. Thus, the consumer must clean them regularly. Such means water use, and if solvents are added during the cleaning activity, environmental effects like off-gassing are produced. Besides, water moistens the inner foams aiding in bacteria growth (Vieira et al., p. 2).     

Recycle

Recycling is when the consumer turns in the material or product to a recycling center or sends it back to the manufacturer for taking apart and recycling. Although cleaning is vital for game, practice, soft-ground, firm-ground, indoor, and turf cleats, recycling is essential in sparing the environment because metal, rubber, and plastic cleats are non-biodegradable. However, the recycling process brings air, water, and chemical pollution when adhesives like glue are used. According to Ritchie & Roser (p. 3), adhesives are used in plastic recycling. However, adhesives emit volatile organic compounds with some solvents used in recycling plastics, producing acrylic acid with a characteristic tart and acrid smell, thereby an air pollutant. Similarly, rubber waste is not biodegradable, calling for recycling methodologies like converting rubber powder into elastic-plastic materials via the mechano-chemical method in reclamation (Yehia, p. 1). 

Waste Management

Waste management involves the stage where the material or product ends up at the dump. Rubber is a critical material for some cleat types. However, Yehia et al., (p. 1) point out that rubber waste management has proved to be a primary challenge because of the huge quantities of rubber goods and scrap tires added to the dumpsites every year. The challenge exists globally where stockpiling and landfilling have become the norm, posing numerous undesirable public health and environmental attributes. When the rubber material from cleats piles up with other rubber wastes, a breeding site for mosquitoes is created. Mosquito breeding is known to cause serious health risks such as malaria. Also, the rubber residues develop a hazardous oily environment, acid smoke, and constitute fires that produce smoke, bringing forth the greenhouse effect. Therefore, rubbers and other thermoplastic materials must undergo vulcanizing as a means of maintenance because they are not biodegradable (Yehia, p. 1).

In this essence, putting rubber cleat material on the ground poses environmental hazards. They are non-biodegradable and act as breeding sites for mosquitoes. When the rubber and plastic cleats catch fires, they produce billowing smoke that brings forth greenhouse effects by damaging the ozone layer. Thus, if rubber and plastic cleat materials are not separated from biodegradable materials, they would cause serious problems. Similarly, metal cleats are not biodegradable. Putting them to the ground means that they may injure people, especially vulnerable populations like children. However, wastes from renewable sources can be constructively managed in the derivation of polymeric foams, a perspective in property enhancement in the modern world characterized by increased attention to environmental issues (Agrawal et al., p. 274). Renewable sources can produce foams, although some concerns like low thermal stability, high flammability, and low mechanical strength prevail.  

Conclusion

         Waste of cleats can be managed in the product life cycle. The steps of raw materials acquisition, manufacturing, processing, and formulation, distribution and transportation, use, re-use, and maintenance, recycle and waste management face waste and pollution concerns, directly or indirectly. For instance, when acquiring the raw materials, various by-products are produced affecting the extractors. Similarly, transportation and distribution sees means like cars and trucks emitting carbon dioxide and smoke known for bringing forth greenhouse effects. Such causes air and water pollution because of the vapors, dusts, gases, fumes and other chemicals released into the atmosphere and water bodies. The extractors and those around are prone to hazardous health effects via inhalation, skin absorption and physical injuries. The pollution problems can be overcome by incorporating property-surface fillers and material modification with or without surface treatment (Agrawal et al., p. 274), while also ensuring that everyone is made aware of workplace safety.         

Bibliography

Agrawal, Anuja, Raminder Kaur, and R. S. Walia. "PU foam derived from renewable sources: Perspective on properties enhancement: An overview." European Polymer Journal 95 (2017): 255-274. https://www.sciencedirect.com/science/article/pii/S0014305717302604?casa_token=S1YYCFd8zuwAAAAA%3AhdQ_zaC25yGeiaiVUkQllmOrtyCL_fga67pkOsborbX_yVeaFGyGaHMq9YTCP81NkC9e-Jdt.

Brandt, Luise Ørsted, Jannie Amsgaard Ebsen, and Kirstine Haase. "Leather Shoes in Early Danish Cities: Choices of Animal Resources and Specialization of Crafts in Viking and Medieval Denmark." European Journal of Archaeology 23.3 (2020): 428-450. https://www.cambridge.org/core/journals/european-journal-of-archaeology/article/abs/leather-shoes-in-early-danish-cities-choices-of-animal-resources-and-specialization-of-crafts-in-viking-and-medieval-denmark/B57CEFFB2349D6B9B297B22DE10EB68B.

Centres for Disease Control and Prevention. Special Niosh Hazard Review. 2014. Rubber Products Manufacturing Industry (93-106) | NIOSH | CDC

Chertow, Marian, and Jooyoung Park. “Rubber Waste.” Rubber Waste - an Overview | ScienceDirect Topics, 2019, https://www.sciencedirect.com/topics/earth-and-planetary-sciences/rubber-waste.

Heidt JR, Robert S., et al. "Differences in friction and torsional resistance in athletic shoe-turf surface interfaces." The American journal of sports medicine 24.6 (1996): 834-842. https://journals.sagepub.com/doi/abs/10.1177/036354659602400621?casa_token=Y8eHWFPC7mEAAAAA%3AYmHdnkUOpiIc1RiNuQv6aK-bDCuR0skQJIqP0SfVgLIJlfkJh-Hr8TIszrp3iyUuoh6MPB_ZXBw. 

Hennig, Ewald M. "The influence of soccer shoe design on player performance and injuries." Research in Sports Medicine 19.3 (2011): 186-201. https://www.tandfonline.com/doi/full/10.1080/19424281003691999?scroll=top&needAccess=true.

Kolomaznik, Karel, et al. "Leather waste—potential threat to human health, and a new technology of its treatment." Journal of Hazardous materials 160.2-3 (2008): 514-520. https://www.sciencedirect.com/science/article/pii/S0304389408004007?casa_token=kQxNth0tqxgAAAAA%3AGHAxuyH1_ibWkoRhWu9BLjr7i2dGoOVkPkhz2Z6MlJQ-x0HO2Pwmk1L7EAhQnSjg_N2MBuwz.

O’Malley, Michael A., et al. “Occupational vitiligo due to unsuspected presence of phenolic antioxidant byproducts in commercial bulk rubber.” Journal of occupational medicine (1988): 512-516.

Ritchie, Hannah, and Max Roser. “Plastic Pollution.” Our World in Data, 1 Sept. 2018, https://ourworldindata.org/plastic-pollution.

Vieira, Marcus Fraga, et al. “Footwear and Foam Surface Alter Gait Initiation of Typical Subjects.” PLOS ONE, Public Library of Science, 13 Aug. 2015, https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0135821.

Yaqub, G., Hamid, A., Khan, N., Ishfaq, S., Banzir, A., & Javed, T. (2020). Biomonitoring of Workers Exposed to Volatile Organic Compounds Associated with Different Occupations by Headspace GC-FID. Journal of Chemistry, 2020.

Yehia, Abbas. Recycling of Rubber Scrap and Its Utilization’s. Nov. 2004, https://www.researchgate.net/profile/Abbas-Yehia/publication/240546761_Recycling_of_Rubber_Waste/links/545f3a360cf27487b44f4ca6/Recycling-of-Rubber-Waste.pdf.