Tali Forsyth

ATLS 4519 Sustainable Design​

University of Colorado Boulder​

Instructor: Eldy Lazaro

Blundstone Lug Boot Life Cycle Assessment

Blundstone boots have gained popularity over the years throughout the world. Their Lug boot has a chunkier sole for better traction and a waterproof leather finish. Blundstone typically attracts outdoor enthusiasts, therefore many of their customers care about the environment and their impacts on the environment. Those who care about the environmental impact of their purchases will find the following LCA particularly interesting. I chose to research the Life cycle of the Blundstone Lug Boot because I own a pair and I was interested in its lifecycle, especially because Blundstone advertises that they are mindful of their impact on the planet. This qualitative Life Cycle Analysis (LCA) will dive into the details of the Blundstone Lug boot, from the raw materials acquisition to the product manufacturing, to transportation and distribution, use, reuse and maintenance, and recycling and disposal. Specifically, raw materials and energy as inputs in every phase of the product’s life cycle, and waste and pollution as outputs will be discussed throughout the lifecycle of the boot. The scope of my analysis in the raw materials acquisition phase focuses on the four main materials of the Lug boot: rubber, steel, leather, and polyurethane. In the product manufacturing phase, my analysis focuses on the assembly of all the individual pieces to put the boot together. My analysis of the transportation and distribution phase focuses on the shipping throughout the lifecycle. In the Use, Reuse, and Maintenance phase, I focus on the upkeep of the boots. The scope of my analysis in the recycling and disposal phase focuses on packaging and disposal of the boots. Those who read this LCA will gain a better understanding of all aspects of the life cycle of a Blundstone lug boot, which may inform them about their future or past purchases from Blundstone.

Raw Materials

The materials used to make the Blundstone Lug Boot are leather, rubber, steel, and polyurethane. Blundstone works with four partners: OSI Group, Comando, Textiles Leon, and Lefarc. 

Raw Materials Acquisition

Steel is used for the shank of the boot, which adds support right under the arch of the foot. The Raw Materials that go into steel are coal, pulverized coal, and iron ore. [1] Coal mining is very damaging to natural ecosystems, landscapes, humans, animals, and plants. Strip mining, a method of coal mining, can damage underground aquifers that supply drinking water or water for agriculture. Coal mining produces air pollution including methane emissions which contribute to climate change and particulate matter emissions which negatively impact human health. [2][4] Similarly, Iron Ore mining is very damaging to humans, landscapes, and our atmosphere. 95% of iron ore mined each year is used by the steel industry. Iron Ore large surface mining requires the destruction of habitats, large quantities of freshwater, and contamination of nearby soil and water. Acid drainage, which pollutes water with heavy metals and acid, can continue for thousands of years after mining activities have ended. [3]

Leather is used for the lining of the boot. The raw materials that go into making leather are skins, water, chemicals, and energy. Skins come from farms or slaughterhouses. Leather tanning is the process of turning skins into leather, using chemicals, water, time, and energy. Chrome tanning was invented in the mid-19th century and is the method used to make the Blundstone Lug Boot. Its main benefits are that it is much quicker than the other tanning process, vegetable tanning, it only takes a day or 2, and the leather is also more supple and vibrant. The main drawbacks of chrome tanning are that it produces toxic waste, and causes health issues to surrounding populations. According to a Life Cycle Assessment of a leather shoe supply chain, the slaughterhouse is the most environmentally impactful stage due to the transport of the animals, often animals are transported across countries. The second most impactful phase was the tanning phase due to the high quantities of chemicals used. [6]

The sole of the Lug Boot is made from Rubber. Rubber can either be made naturally from a rubber tree or synthetically from petroleum. Most shoe soles are now made of synthetic rubber, since I could not find any specific information about the type of rubber Blundstone uses, I have assumed they use synthetic rubber. Since synthetic rubber’s main raw material is petroleum, it has a worse environmental impact than natural rubber. For every metric ton of Synthetic Butadiene Rubber, 5.55 metric tons of CO2 is emitted into the atmosphere. Synthetic rubbers emit >80% more CO2 emissions compared to natural rubbers.[8] Crude Oil extraction and refining is the main contributor to synthetic rubber's environmental impact. Petroleum refineries generate air, water, and soil pollution. Air pollutants include hazardous and toxic chemicals such as benzene, toluene, ethylbenzene, xylene, particulate matter, nitrogen oxides, carbon monoxide, methane, hydrocarbons, and more.[9] These pollutants affect human health as well as ozone degradation and global climate change. Many thousands of pounds of these pollutants are emitted into the environment every year. Water pollution occurs through both deep-injection wells and surface water. [9]

Polyurethane is the material used in the midsole of the Blundstone Lug Boot. The raw materials that makeup polyurethane are polyols, isocyanate, water, surfactant, and a catalyst.[10] There are 2 categories of chemicals in Polyurethane chemistry: Side A and Side B.[11] Side A chemicals irritate the skin, cause respiratory problems, trigger asthma, and destroy mucus linings of respiratory surfaces. Side B chemicals have serious effects on the environment, and aquatic organisms, and can cause serious burns if ingested, and build up in the brain or liver. Flame retardants present in polyurethane chemistry bioaccumulate in animals, especially aquatic organisms. When humans eat these organisms, they consume the flame retardants. Aquatic species that consume flame retardants deal with hormone imbalance and decreased reproductive health and survival. Due to the bioaccumulation of these chemicals, human health is also impacted including birth defects, cancers, poor immune health, and developmental and reproductive effects. Chemical production of polyurethane also impacts crops largely due to its effect on soil. Soil pollutants lower crop yields, quality, and nutritional content.

Product Manufacturing

The materials used during the manufacturing process are mostly the by-products of the raw materials discussed above. Leather, steel, rubber, and polyurethane are the 4 main materials used, along with glue, and thread to attach all the different pieces. It is difficult to find specific information about the glue Blundstone uses but there are likely negative environmental effects due to the chemicals in the glue. The thread used also likely has some effect on the environment however it is likely negligible compared to the main 4 materials of the boot.

Transportation and Distribution

The materials associated with transportation and distribution are mostly packaging. Blundstone makes 99% of its packaging with some level of recycled materials and is designed for all components to be recoverable at end-of-life.[12] Taking this into account, their shoe boxes are likely made with recycled materials and are likely recyclable. I assume during the shipping process, there are probably other materials such as plastic wrap to hold together large amounts of boxes.

Use, Reuse, Maintenance

The only material associated with the Use, Reuse, and Maintenance phase is leather conditioner. I could not find what ingredients are used in leather conditioners, but based on their smell, I assume they contain chemicals that could be harmful to the environment. The packaging of the leather conditioner can vary depending on the brand, but the Blundstone brand packaging looks to be made of aluminum or a similar metal. The packaging of the leather conditioner is likely made from recycled materials and recyclable considering Blundstone’s packaging standards.

Recycling and Disposal

The main materials associated with recycling and disposal of the boots are likely glue and thread. Glue and thread might be used to repurpose the boot, however, Lug Boots cannot be resoled. If a person chooses to donate the boot to a thrift store or repurposing program there may be packaging associated with the transportation like a trash bag or cardboard box. 

Raw Materials Sources

Steel

1 “Environmental Impact of Steel Production.” The World Counts, 

www.theworldcounts.com/challenges/planet-earth/mining/environmental-impact

-of-steel-production. Accessed 18 Feb. 2024.

2 The Environmental Impacts of Coal, 

www.greenpeace.org/static/planet4-aotearoa-stateless/2018/05/enviro-impacts-

of-coal.pdf. Accessed 19 Feb. 2024.

3 “Environmental Impacts of Iron Ore Mining.” UKGBC, 12 Feb. 2024, 

ukgbc.org/our-work/topics/embodied-ecological-impacts/iron-ore/#:~:text=Cont

amination%20and%20pollution%20of%20soil%20and%20water.&text=Dust%2

0and%20particulate%20matter%20released,of%20nearby%20humans%20and

%20animals.

4 Renzulli, P.A.; Notarnicola, B.; Tassielli, G.; Arcese, G.; Di Capua, R. Life Cycle 

Assessment of Steel 

Produced in an Italian Integrated Steel Mill. Sustainability 2016, 8, 719. 

https://doi.org/10.3390/su8080719 There Is No Such Thing as “Clean Coal”: 

Coal Mining Can ..., www.nrdc.org/sites/default/files/coalmining.pdf. Accessed 

19 Feb. 2024. 

Leather

5 “Lefarc.” Español, 25 Sept. 2021, www.lefarc.com/en/home/. 

6 Marta Rossi, Alessandra Papetti, Marco Marconi & Michele Germani (2021) Life cycle 

assessment of a leather shoe supply chain, International Journal of Sustainable 

Engineering, 14:4, 686-703, DOI: 10.1080/19397038.2021.1920643

Rubber

7 Li, Wei & Wang, Qiaoli & Jin, Jiajia & Li, Sujing. (2014). A life cycle assessment case 

study of ground rubber production from scrap tires. The International Journal of 

Life Cycle Assessment. 19. 1833-1842. 10.1007/s11367-014-0793-3. 

Rasutis, Daina. Comparative Life Cycle Assessment of Conventional And ..., 

Aug. 2014, core.ac.uk/download/pdf/79572799.pdf. 

8 “Rubber Chronicle 19: Co2e Emissions of Natural Rubber, Neoprene, Geoprene and 

SBR.” YULEX®, 19 July 2023, 

www.yulex.com/post/rubber-chronicle-19-co2e-emissions-of-natural-rubber-ne

oprene-geoprene-and-sbr.

9 “Environmental Impact of the Petroleum Industry - Gov.Epa.Cfpub.” Environmental 

Update #12, Hazardous Substance Research Centers, June 2003, 

cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.files/fileID/14522.

Polyurethane

10 Raquel Silva, Ana Barros-Timmons, Paula Quinteiro, Life cycle assessment of fossil- 

and bio-based polyurethane foams: a review, Journal of Cleaner Production, 

Volume 430, 2023, 139697, ISSN 0959-6526, 

https://doi.org/10.1016/j.jclepro.2023.139697.

11 Adetunji, Charles & Olaniyan, Olugbemi & Anani, Osikemekha & Inobeme, Abel & 

Mathew, John. (2021). Environmental Impact of Polyurethane Chemistry. 

10.1021/bk-2021-1380.ch014.

12 Annual Report and Action Plan, blundstone.com/media/wysiwyg/PDFs/CY2023_Final_Annual_Report_Action_Plan_Blundstone.pdf. Accessed 12 Apr. 2024.

Embodied Energy 

Raw Materials Acquisition

There is energy associated with the acquisition of raw materials such as coal, oil, and cows. The main energy use associated with coal and oil acquisition is from transportation and extraction. For every metric ton of Synthetic Butadiene Rubber, 5.55 metric tons of CO2 is emitted into the atmosphere. Synthetic rubbers emit >80% more CO2 emissions compared to natural rubbers.[16] Rubber for Blundstones is produced in Thailand, the world's #1 rubber manufacturer. The energy mix of Thailand is 43.7% oil, 26.4% natural gas, 12.4% coal, 16.6% biofuels and waste.[12] Hydro, solar, and wind are barely used. Steel production is highly energy intensive, it is the world’s most energy-consuming industry. On average, for every ton of steel produced 20 gigajoules of energy is used.[4] The energy used to treat the leather of the boot is mainly associated with the chrome tanning process discussed in the raw materials section. The leather is treated in Adelaide, Australia where the energy mix is 34% coal, 32% oil, and 25.7% natural gas, so most likely a nonrenewable energy source is used to treat the leather.[8] It is not clear where the polyurethane for the boots is manufactured, so I am assuming it is made in China because Blundstone sources a lot of their materials from China. The energy mix of China is 61% coal, 18.1% oil, and 8% natural gas, so most likely the polyurethane is made using coal energy. [9]

Product Manufacturing

The energy associated with putting all the pieces of the Lug Boot together is mostly the energy used in the factory for the lights and machinery. There are 4 main countries where Blundstone’s product manufacturing occurs; China, India, Vietnam, and Mexico.[14] All of these countries use a majority of nonrenewable energy sources. China, India, and Vietnam use coal more than any other type of energy, which is particularly harmful to the environment. [8][9][10][11][12][13]

Transportation and Distribution

For the leather of the boot to be produced, cows are shipped from New Zealand to China. International shipping accounts for about 3% of the world’s greenhouse gas emissions.[7] The primary source of these emissions is the combustion of petroleum-based fuels such as coal, crude oil, diesel, natural gas, etc. Once the cows reach China for leather production, they are transported via truck.[14] Once the leather is produced, it is transported via freight ship from China to Australia for the final treatment process called greasy kip.[14] All the materials needed to put the boot together are then shipped to manufacturing factories in India, Vietnam, Mexico, China, or Tasmania.[14] Once the boot is assembled, it is shipped to distributors worldwide.[14] In the US, all Blundstone boots are shipped to a warehouse in Pennsylvania, which then distributes them to retailers all over the US.

The Blundstone warehouse in Derrimut sends usable outer cartons and pallet pads to Blundstone HQ in Tasmania via ship.[1]

Use, Reuse, Maintenance

The main energy use during this phase would be transportation to get maintenance. If the boots need repair, they need to be taken or shipped to a repair facility. All leather boots need regular upkeep with leather conditioner, so there is energy associated with either purchasing leather conditioner at a store or buying it online.

Recycling and Disposal

Packaging

Blundstone is pretty intentional about its packaging end-of-life. 99% of their packaging is designed to have all components be recoverable at end-of-life and the company has recycling programs for paper, cardboard, and soft plastics.[1] The process of recycling cardboard does use energy, however, it uses ~75% of the energy used in making new cardboard.[5] The energy used in the cardboard recycling process is mostly from machines such as the mill that shreds it into small pieces and a pulping machine that uses water and chemicals to break down the cardboard into fibers.

Boots

I could not find any information about recycling the shoes or their parts so most likely when boots are worn, they will go to the landfill or an incinerator. There are a couple of other options that a consumer could choose including donating their boots. Donated boots may be refurbished, however, most Blundstone boots are not able to be resoled. Sometimes donated items still get sent to landfills, for example, if something is not sold at a thrift store, it might still end up in the landfill. Another option is to find a shoe drive or recycling program such as TerraCycle that will find buyers who will take bits of the shoes and make them into flooring, furniture, containers, soundproofing materials, and more.[2] The most significant energy associated with most of these options would likely be from transportation. If the boots go to an incinerator, there would be energy used to power the incinerator. 

Embodied Energy Sources

1 Annual Report and Action Plan, blundstone.com/media/wysiwyg/PDFs/CY2023_Final_Annual_Report_Action_Plan_Blundstone.pdf. Accessed 12 Apr. 2024.

2 “Ask a Sustainability Expert: How Do I Recycle My Worn-out Shoes? - Fashionista.” How to Recycle Shoes, fashionista.com/2020/02/how-to-recycle-shoes-sneakers-heels. Accessed 12 Apr. 2024.

3 “Company Overview.” Company Overview, www.blundstone.com/overview. Accessed 12 Apr. 2024.

4 “Environmental Impact of Steel Production.” The World Counts, www.theworldcounts.com/challenges/planet-earth/mining/environmental-impact-of-steel-production. Accessed 12 Apr. 2024.

5 Gemeš, Nikola. “Everything You Need to Know about Cardboard Recycling.” GreenCitizen, 19 Mar. 2024, greencitizen.com/blog/cardboard-recycling/.

6 “How It’s Made. Polyurethane. inside Factories.” YouTube, YouTube, 14 Jan. 2022, www.youtube.com/watch?v=XQulKLh8Dts.

7 “How Much Does the Shipping Industry Contribute to Global CO2 Emissions?” Sinay, 22 Sept. 2023, sinay.ai/en/how-much-does-the-shipping-industry-contribute-to-global-co2-emissions/#:~:text=In%202022%2C%20international%20shipping%20alone,contributor%20to%20global%20carbon%20pollution.

8 Iea. “Australia - Countries & Regions.” IEA, www.iea.org/countries/australia/energy-mix. Accessed 12 Apr. 2024.

9 Iea. “China - Countries & Regions.” IEA, www.iea.org/countries/china/energy-mix. Accessed 12 Apr. 2024.

10 Iea. “India - Countries & Regions.” IEA, www.iea.org/countries/india/energy-mix. Accessed 12 Apr. 2024.

11 Iea. “Mexico - Countries & Regions.” IEA, www.iea.org/countries/mexico. Accessed 12 Apr. 2024.

12 Iea. “Power Generation Mix in Thailand, 2020 – Charts – Data & Statistics.” IEA, www.iea.org/data-and-statistics/charts/power-generation-mix-in-thailand-2020. Accessed 12 Apr. 2024.

13 Iea. “Viet Nam - Countries & Regions.” IEA, www.iea.org/countries/viet-nam. Accessed 12 Apr. 2024.

14 “Open Sourcemap - Development Environment #sourcemap.” Open Sourcemap - Development Environment, open.sourcemap.com/maps/63dd716a1d62655f39495244/things. Accessed 12 Apr. 2024.

15 “Responsible Use of Resources, Managing Emissions & Reducing Environmental Impact.” Responsible Use of Resources, Managing Emissions & Reducing Environmental Impact, www.blundstone.com/our-commitment/planet. Accessed 12 Apr. 2024. 

16 “Rubber Chronicle 19: Co2e Emissions of Natural Rubber, Neoprene, Geoprene and 

SBR.” YULEX®, 19 July 2023, 

www.yulex.com/post/rubber-chronicle-19-co2e-emissions-of-natural-rubber-ne

oprene-geoprene-and-sbr.

Waste and Pollution

Raw Materials Acquisition

Steel

There is a significant amount of waste and pollution associated with acquiring raw materials to make steel, including mine waste, air pollution, soil pollution, and water pollution. When extracting coal, mine waste is generated in very large quantities, it is flammable and prone to spontaneous combustion so it must be disposed of properly. Mine wastes contain heavy metals that may leach into rivers, streams, or groundwater. Water pollution and acid drainage can continue for thousands of years after mining has stopped. Petroleum extraction also generates air pollution from methane emissions which contributes to climate change and particulate matter emissions which negatively affects human health. Air pollution can also occur in the form of nitrous oxide, carbon dioxide, carbon monoxide, or sulfur dioxide from diesel generators, trucks, and other equipment. On average, for every ton of steel produced, 1.83 tons of CO2 is emitted.  [5][7]

Leather

Waste associated with the acquisition of leather is mostly from leather tanning and scraps of hair and skin. Leather tanning creates waste water and chemical waste. There is also pollution associated with the machinery used for leather tanning. Hair and skin scraps can be turned into collagen but often just go to waste. [3]

Rubber

There is water and air pollution associated with acquiring the raw materials to make rubber. Petroleum extraction contributes to both types of pollution. Air pollution from petroleum extraction is a major source of hazardous and toxic air pollutants such as benzene, toluene, ethylbenzene, and xylene, as well as particulate matter such as nitrogen oxides, carbon monoxide, methane, hydrocarbons, and more. Some of the chemicals released cause cancer, are responsible for developmental and reproductive issues or can aggravate respiratory conditions. Water pollution from petroleum extraction can occur while disposing of wastewater using deep-injection wells, some of the waste in these wells can end up in aquifers and groundwater. Contaminated water may be wastewater from desalting, cooling towers, stormwater, distillation, or cracking. Wastewater may contain oil residuals or other hazardous waste. There may also be soil pollution associated with petroleum extraction however it is generally less significant than air or water pollution. [6]

Polyurethane

Acquisition of polyurethane negatively impacts crops and can cause bioaccumulation of flame retardants. The quality and nutritional status of crops are dependent on soil conditions, which can be contaminated during polyurethane acquisition. Flame retardants used to acquire polyurethane can build up in the bodies of animals if they get into waterways. Humans or animals that eat an animal with flame retardants in their fatty tissue or liver will consume the flame retardants as well. [4]

Product Manufacturing

Manufacturing blundstone boots has some waste associated with it. The main source of waste during manufacturing is leather. Cutting the leather into the correct shape leaves scraps, and when the leather is attached to the sole, it is trimmed again. I could not find specific information regarding emissions and pollution from the factories where the boots are manufactured, but they produce emissions and pollution to power their machines and lights. [8]

Transportation and Distribution

Transportation and Distribution produce a significant amount of pollution. Blundstone utilized international shipping during manufacturing and distribution. International shipping accounts for 3% of the world’s greenhouse gas emissions. The primary source of these emissions is the combustion of petroleum-based fuels such as coal, crude oil, and diesel. Cargo ships are reported to produce 16.14 grams of CO2 per kilometer for each metric ton of cargo they carry, whereas container ships release an annual average of 140 million metric tons of carbon dioxide. [9]

Use, Reuse, Maintenance

Once an individual owns a Blundstone Lug Boot, the maintenance associated with the boot is primarily using leather conditioner. The waste associated with leather conditioners is mainly water waste, waste from chemical ingredients, and packaging waste. When using a leather conditioner, there may also be waste if the person chooses to use paper towels instead of rags or other reusable towels. Manufacturing leather conditioners likely produces emissions but I could not find specific information on what kind of emissions or how much. [11]

Recycling and Disposal

Blundstone as a brand has committed to some sustainable practices as it relates to recycling and disposal at their facilities. The facilities they partner with may not be committed to the same practices. At Blundstone facilities, they have implemented water recycling which saves approximately 5 liters of water for every gumboot they manufacture, about 1 million liters of water saved per year. The Blundstone facility in Derrimut, near Melbourne Australia, sends usable outer cartons and pallet pads to Blundstone headquarters for re-use to package new items. 98% of Blundstone packaging has on-pack labels to inform customers about correct disposal. 99% of their packaging is designed to have all of the components recoverable at end-of-life. Blundstone has recycling programs for paper, cardboard, and soft plastics. Blundstone also aims for 36% of its on-site waste to be diverted from landfills. Their shoe boxes are made with 100% recycled materials and are 100% recyclable. [1][10] I couldn’t find specific information about the recycling and disposal of the Lug Boot, most likely when boots are worn, they will go to the landfill or an incinerator. There are a couple of other options that a consumer could choose including donating their boots. Donated boots may be refurbished, however, most Blundstone boots are not able to be resoled. Sometimes donated items still get sent to landfills, for example, if something is not sold at a thrift store, it might still end up in the landfill. Another option is to find a shoe drive or recycling program such as TerraCycle that will find buyers who will take bits of the shoes and make them into flooring, furniture, containers, soundproofing materials, and more. [12]

Waste Sources

1 Annual Report and Action Plan, blundstone.com/media/wysiwyg/PDFs/CY2023_Final_Annual_Report_Action_Plan_Blundstone.pdf. Accessed 26 Mar. 2024.

2 “Application of Life Cycle Assessment to Footwear.” Environmental Update #12, www.researchgate.net/publication/225840953_Application_of_life_cycle_assessment_to_footwear. Accessed 26 Mar. 2024.

3 English, Nick. “Is Lefarc the World’s Most Sustainable Leather Tannery?” Stridewise, 1 Mar. 2024, stridewise.com/lefarc-tannery/.

4 Environmental Impact of Polyurethane Chemistry, www.researchgate.net/publication/351811523_Environmental_Impact_of_Polyurethane_Chemistry. Accessed 26 Mar. 2024.

5 “Environmental Impact of Steel Production.” The World Counts, www.theworldcounts.com/challenges/planet-earth/mining/environmental-impact-of-steel-production. Accessed 26 Mar. 2024.

6 “Environmental Impact of the Petroleum Industry - Gov.Epa.Cfpub.” Environmental Update #12, cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.files/fileID/14522. Accessed 26 Mar. 2024.

7 “Environmental Impacts of Iron Ore Mining.” UKGBC, 12 Feb. 2024, ukgbc.org/our-work/topics/embodied-ecological-impacts/iron-ore/#:~:text=Contamination%20and%20pollution%20of%20soil%20and%20water.&text=Dust%20and%20particulate%20matter%20released,of%20nearby%20humans%20and%20animals.

8 “How Leather Boots Are Made.” Thursday Boot Company, blog.thursdayboots.com/design/how-leather-boots-are-made/#:~:text=The%20big%20piece%20of%20leather,off%20the%20bottom%20is%20trimmed. Accessed 26 Mar. 2024.

9 “How Much Does the Shipping Industry Contribute to Global CO2 Emissions?” Sinay, 22 Sept. 2023, sinay.ai/en/how-much-does-the-shipping-industry-contribute-to-global-co2-emissions/#:~:text=In%202022%2C%20international%20shipping%20alone,contributor%20to%20global%20carbon%20pollution.

10 “Responsible Use of Resources, Managing Emissions & Reducing Environmental Impact.” Responsible Use of Resources, Managing Emissions & Reducing Environmental Impact, www.blundstone.com/our-commitment/planet. Accessed 26 Mar. 2024.

11 “Welcome to Nikwax: Outdoor Innovation.” Nikwax, www.nikwax.com/en-us/ingredients/. Accessed 26 Mar. 2024. 

12 https://fashionista.com/2020/02/how-to-recycle-shoes-sneakers-heels