Design Life-Cycle
assess.design.(don't)consume
Lily Dykstra
ATLS 4519 - Sustainable Design Class
Altas Institute, University of Colorado Boulder
Instructor Eldy Lazaro
Botts' Dots Life Cycle Assessment
Botts' Dots are road dots commonly used in warm weather states to mark driving lane boundaries and notify drivers if they leave their lanes. Botts' Dots are made out of Polyethylene Terephthalate, more commonly known as PET, and epoxy adhesives. The scale of the following life cycle is one singular Botts' Dot. The life cycle of each element can be analyzed to understand each step of production: including raw materials, embodied energy, and waste and pollution. Each breakdown involves five internal steps: raw material acquisition; product manufacturing; transportation and distribution; use, reuse, and maintenance; and final disposal and recycling. Throughout this assessment, my goal is to educate readers on the environmental impact of items we use and encounter in daily life. The ideal audience for this analysis is environmentally conscious drivers and people who interact with the road a lot, such as road construction workers or Botts’ Dots installation or manufacturing workers. I hope readers will come away with a deeper understanding of the roads they drive on every day and their broad-scale impact.
In the Raw Materials section, I discuss the raw material inputs used to make Botts’ Dots, PET, and epoxy. In the Embodied Energy section, I outline the energy inputs involved in creating PET, epoxy, and subsequently Botts' Dots. Lastly, in the Waste and Pollution section, I cover the waste and pollution outputs associated with each step in the life cycle assessment. I explore the details of all three sections via the five internal steps mentioned above (acquisition; product manufacturing; transportation and distribution; use, reuse, and maintenance; and final disposal and recycling).
I am particularly interested in Botts’ Dots because I grew up in California, a Botts’-Dots-using state. Across California, these road markers line every lane. They were a key element of how I learned to drive and I am highly aware of the safety support they offer drivers. They are an inconspicuous everyday item about which I never thought twice. Now, I consider these dots in a new and somewhat apprehensive light after learning the energy and material cost, as well as waste involved in their production, installation, and disposal.
Raw Materials:
Raw Material Production and Acquisition:
As previously mentioned, PET is one of two main components in producing Botts' Dots. The PET (Polyethylene terephthalate) is a combination of petroleum-derived ethylene glycol and purified terephthalic acid, commonly known as PTA. The ethylene glycol is first derived from crude oil and then distilled into its purest form at an oil refinery (US Energy and Information Administration). PTA is created when paraxylene is oxidized in acetic acid, using manganese or cobalt acetate to catalyze the reaction (Valco). Once the PTA and ethylene glycol are each prepared, they are mixed together and then added to a catalytic reactor to create PET. After the PET cools and solidifies, they are cut into pellets (Wankai).
In order to make the PET part of the Botts’ Dot, plastic colorants are mixed with the pellets prior to melting (Trocellen). These color additives can be organic or inorganic pastes, powders, etc. The most suitable colorants are organic compounds from the Anthraquinone chemical family (SpecialChem).
The second element in Botts' Dots is the epoxy adhesive which secures the PET to the road. Epoxies are an organic compound made up of a thermosetting epoxy polymer and hardener (Industrial Quick Search). They are made by mixing epichlorohydrin (ECH) with bisphenol A (BPA). The finalized PET and epoxy must be transported to the production site. They are transported in polypropylene woven sacks.
Every step taken to produce these raw materials requires energy and fuel for machinery and chemical equipment.
Product manufacturing
The road dots are made via PET and epoxy, both of which are produced in China and then shipped to the US for final Botts' Dots production. The PET pellets specifically are transported to the thermoplastic injection factories in the U.S. via hopper trucks and cargo ships in polypropylene woven sacks (Union Pacific). Once they arrive at the U.S. factories, the PET pellets are melted and injected into Botts’-Dots-shaped molds (via thermoplastic injection) (Mold Plastic Injection). In these molds, the pellets then undergo cooling, molding, and solidification processes. During the production in China, the epoxy which attaches the dots to the road is made via resin machines (Science Direct). These machines create the final liquid product that is then applied to injection-molded PET in order to harden them to the roads. The finalized epoxy is transported to the U.S. for use, most likely packaged in bottles and in boxes, and then shipped to the U.S.. Everything aforementioned requires fuel and energy to use the machines and transport products.
Transportation and distribution
PET and epoxy are produced in China and transported to the U.S. for Botts' Dots production. Since Botts' Dots are U.S.-produced and -based, they will most likely be driven across the country to other warm states. It is unknown if there is a central location where all Botts' Dots are produced and stored until installation. The finalized Botts' Dots are most likely stored in an unknown packaging vehicle during distribution. Everything aforementioned requires fuel and energy to use the machines and transport products.
Use, reuse, maintenance
The PET-shaped dots are installed onto the road with epoxy adhesives by humans. They are replaced roughly every 6 months due to wear and tear from car traffic (Kohlstedt). Every time they need replacement, fuel is used to drive out to the location and human energy is used to replace the dots. The removal process includes: use of a heat gun to loosen the attachment to the road, use of a pry bar to remove the dot from the road, and application of chemicals to break down the remaining epoxy (Entropy Resin). Additionally, new materials are used for reinstallation, so the whole process of injection molding and epoxy manufacturing must be completed again to make a new Botts’ Dot.
Final disposal/recycling
Both PET and epoxy are recyclable, but due to their high replacement rate, I am skeptical that they are in good enough condition for recycling. PET is recyclable via mechanical recycling. The dots are chopped into tiny pellets that can then be shipped to companies and molded into new objects (End Waste Recycle the One). Epoxy is chemically recyclable via “solvolysis, pyrolysis, or nitric acid treatment, involv[ing] harsh chemicals and the application of high temperatures and pressures.” (NLM) All of these processes need energy and fuel during transport, chemical and mechanical recycling processes, and shipping materials to different companies. All of the polypropylene woven bags are shredded and sorted to be fully recycled; however, most of the shredded pieces end up in landfills.
Embodied Energy:
Raw Material Acquisition and Production:
Botts' Dots are made up of PET and epoxy. PET and epoxy are primarily produced in China and the U.S. (Market Research Reports)(Statista). PET is made of purified terephthalic acid (PTA) and ethylene glycol. PTA is a component of acetic acid. Ethylene glycol is derived from crude oil. Crude oil takes 55 MJ/kg to be extracted by drilling. In general, after raw material acquisition, the production of PET uses 79.6-88 MJ/kg (Ashby). The colorants used for PET are often sourced from fungi and plants that contain Anthraquinone, but these colorants can also be synthesized (Science Direct). I could not find information regarding the energy required for colorant synthesis.
Epoxy is made up of Epichlorohydrin and Bisphenol A. Primary epoxy resin production uses 105-130 MJ/kg (Ashby). The U.S. uses fossil fuels (63836 kWh), nuclear (6006 kWh), and renewable (8912 kWh) sources of energy. China uses 25344 kWh in fossil fuels, 733kWh in nuclear, and 4974 kWh in renewable. The values of different types of energy in both China and the U.S. are per capita consumption (Our World in Data).
Additionally, while polypropylene bags are used as packaging, the embodied energy of their production is outside the scope of this life cycle assessment.
Lastly, to understand the acquisition of PET and epoxy, we must consider the energy it takes to transport PET and epoxy from their production sites to Botts' Dots production sites. PET and epoxy are made in China and transported to the U.S. via cargo ship. Operating with an average of 400 km of driving from a factory to the docks in China, a 55-metric ton truck uses 0.284 MJ for every 1 kg of product. Next, assuming the average distance from China to Los Angeles is 10,061.67 km, the energy per 1 kg of PET or epoxy is 0.4024668 MJ (Ashby). During this process in China, human energy is used for packaging, loading, and driving the trucks.
Once the product reaches Los Angeles, human energy is needed to unload and drive trucks to factory and distribution locations. Assuming another 400 km of driving to distribution centers or final packaging facilities, a 55-metric ton truck will use another 0.284 MJ of energy (Ashby).
Product manufacturing:
Both PET and epoxy must be shipped to the U.S. for Botts' Dots production, and then be shaped and manipulated in order to create the dots.
PET is transported in the form of small pellets in polypropylene-woven sacks (Union Pacific). Once they reach the manufacturing center, the PET pellets are heated in a large barrel until they melt. Colorants are mixed during the heating and melting stage so they distribute evenly (Trocellen). The melted and pigmented PET is then poured into Botts'-Dots-shaped molds. Then, they are closed, cooled, and solidified. This is the process of polymer molding (The Roden Group). The polymer molding energy required for PET is 9.36-10.3 MJ/kg, including energy for molding, cooling, and solidification (Ashby).
Epoxy does not require any further manipulation after the initial production. It can be directly applied to the molded dot shape to secure it to the road during installation.
Transportation and distribution:
Additional transportation is needed to distribute Botts' Dots from Los Angeles to Florida, the farthest location of Botts' Dots usage. Using a 55-metric ton truck, it takes 2.5257398 MJ per 1 kg of PET or epoxy to drive from Los Angeles to Florida, 3,557.38 km (Ashby).
Use, reuse, maintenance:
The Botts' Dots are installed by people and they are replaced every 6 months. There is a lot of human energy involved during the installation. Estimating an average of 200 km of driving to the location of installation, it takes 0.142 MJ per kg of Botts' Dots (Ashby). The data for the production and transportation of raw materials repeats with each newly installed dot biannually.
Final disposal/recycling:
PET can be fully recycled, whereas only a small portion of epoxy resin is recyclable (Ashby)(PETcore). It is useful to acknowledge that the energy used during PET and epoxy recycling depends on the technology used and its efficiency. Additionally, it depends on how far the recycling centers are from the installation sites. All of the data mentioned in this section are averages.
Beginning with recycling facilities, assuming an average of 200 km from the collection of Botts' Dots, 0.142 MJ are used during driving (Ashby). In this stage, human energy is used during collection and transportation of the Botts' Dots to the recycling center. Once they reach the recycling center, energy is needed to collect and subsequently sort through the materials.
PET can be recycled mechanically. PET is shredded, melted into small pieces, packaged, and sent out for reuse. Overall, PET recycling uses 33.4-27 MJ/kg, which includes the shredding and melting steps of the recycling process (Ashby).
Only 0.5-1% of epoxy can be chemically recycled (Ashby). Chemical recycling involves using different chemicals to break down epoxy into its base components so that they can be reused. Due to the minimal ability to recycle epoxy, there is almost no data on the energy demand, however many sources deduce that the technology involved has a high energy input. (cite)
Lastly, the polypropylene woven bags used for packaging are 100% recyclable. They undergo the same mechanical recycling process as PET. The shredding, melting, and solidification process takes 45-55 MJ/kg (Ashby).
Waste and Pollution:
Raw Material Acquisition:
Botts' dots are mainly made out of PET and epoxy. Both of these compounds generate quite a bit of water waste, as well as carbon and toxic gas emissions.
In terms of PET, ethylene glycol is a natural gas derived from crude oil. This makes its extraction process environmentally damaging. Terephthalic acid creates 3-10 tons of waste water during its initial production (Scielo). The CO₂ footprint in the primary production of PET is 2.21-2.45 kg/kg and the water usage is 14.7-44.2 l/kg (Ashby). Additionally, the production of PET results in toxic emissions of nickel, ethylbenzene, ethylene oxide, and benzene (Ecology Center).
Epoxy is made of Epichlorohydrin and Bisphenol-A (BPA). The production and use of Epichlorohydrin results in hazardous air and water pollution. During the production process of epoxy resin, there is a significant amount of carcinogenic pollution which is especially dangerous if inhaled (U.S. Environmental Protection Agency). During the production and use of BPA, BPA leaks out of plastics and enters wastewater. The CO₂ footprint for the primary production of the final epoxy product is 4.22-4.56 kg/kg and the water usage is 107–322 L/kg (Ashby). All of these pollutants resulting from BPA are also produced in the overall epoxy resin production.
After production, PET and epoxy must still be shipped from China to the U.S. If we assume 400 km of driving from the factory in China to the Chinese docks, then travel by ship the average distance from China to Los Angeles, and lastly, another 400 km to the Botts' Dots production facility, the average the CO₂ output per 1 kg of PET or epoxy is 0.11 kg (Carbon Care).
Product manufacturing:
The CO₂ footprint in the polymer molding process of PET is 0.749-0.826 kg/kg (Ashby). In general, injection molding contributes to 20% of global CO₂ emissions due to the use of hydraulic oil in the machines. The injection molding process not only releases CO₂, but also releases harmful organic compounds as a result of heating plastics repeatedly (Essentra Components). After heating, the process requires water to cool down the machines and molds. The water is consequently heated and contaminated. Additionally, the process of molding PET into road dots will always generate offcuts or scraps that are disposed of in landfills.
Based on insinuations of many articles, we can assume PET pellets are transported in polypropylene woven sacks. The sacks are considered waste after they complete the product distribution.
Transportation and distribution:
During distribution of finalized Botts’ Dots, transportation is only needed unidirectionally from Los Angeles to Florida, the easternmost location of Botts' Dots usage. The CO₂ emissions are 0.25 kg per 1kg of PET or epoxy driving from Los Angeles to Florida, 3,557.38 km (Carbon Care). The finalized Botts' Dots are likely transported via unknown packaging that ends up being waste.
Use, reuse, maintenance:
Unfortunately, Botts' Dots are not very durable. As previously mentioned, they need to be replaced roughly every 6 months. In terms of carbon emissions, using an average of 200 km of driving, that is 0.02 kg/kg per Botts’ Dot installation (Carbon Care). After replacement, the previous and rundown Botts' Dots are now waste until they are recycled, if they are even in good enough shape to be recycled. The dots are taken off of the road, but epoxy resin is very strong so there will be leftover epoxy on the road where the dots were originally installed. There is also a significant likelihood the Botts’ Dots generate microplastics and larger pieces of PET plastics broken off by cars while driving.
Final disposal/recycling:
While Botts' Dots themselves are not recyclable, their components are. Both PET and epoxy resin are recyclable, however, due to the heavy usage of Botts' Dots, they are not always in the condition to be recycled. For example, only 0.5-1% of epoxy resin is recycled, so 99-99.5% is waste. When epoxy resin is recycled it results in a very large quantity of CO₂ and other pollutant emissions (National Library of Medicine). Plastics such as PET are recyclable. However, like epoxy, they are only recyclable if they are in pure enough condition. When PET is mixed in with additives like colorants, the PET is now considered polluted. Because of this, only 20-22% of PET is recycled. As most Botts' Dots are colored during their manufacturing process, most of the PET of Botts’ Dots is not likely to be recycled (Venture Wells). When they are recycled, the CO₂ emissions are 2.1– 2.6 kg/kg (Ashby).
Polypropylene is fully recyclable in any form it takes, and thus the sacks used for PET distribution are also recyclable. The CO₂ emissions from polypropylene recycling is 2.0–22 kg/kg (Ashby). Unfortunately, most polypropylene ends up in landfills where, as it breaks down, it releases toxic chemicals (Codefine).
For all of the aforementioned recycling processes, we must consider the CO₂ emissions resulting from transportation to the recycling centers. Assuming 200 km, the CO₂ emissions are 0.02 kg for every 1 kg of waste (Carbon Care). Additionally, the recycling process results in air pollution that is known to cause health problems for residents near the processing centers (National Library of Medicine).
It is important to acknowledge that a lot of the time the products and the components of the products do not get repurposed or recycled at all. There will always be PET and epoxy building up in landfills.
Conclusion:
Overall, my research has indicated that Botts’ Dots are not environmentally friendly. They require immense quantities of energy and result in even greater quantities of waste. I have high hopes that Botts’ Dots can be more environmentally friendly, especially if they reuse PET from previous Botts’ Dots or invest in less toxic and more recyclable adhesive. In 2024, many Botts’ Dots are being phased out and we do not know what will happen to them or their materials once they are off the road, let alone if they will be recycled. Road safety is of the utmost importance, but I believe this should never be at the expense of our planetary health. I am excited for a future that prioritizes product development that emphasizes both road safety and also public and environmental health.
Raw Material sources:
Bright Hub Engineering. “Botts' Dots Have Made Driving Safer throughout the World.”
Entropy Resins. “HOW TO REMOVE EPOXY FROM SURFACES.” https://entropyresins.com/blog/2022/09/07/how-to-remove-epoxy-from-surfaces/#:~:text=Heat,the%20epoxy%20off%20the%20surface.
Wankai New Materials Co., Ltd. “What is the PET Plastic Manufacturing Process?.” https://wkaiglobal.com/blogs/what-is-the-process-for-the-manufacture-of-pet-plastic
US Energy Information Administration. “Oil and petroleum products explained.” https://www.eia.gov/energyexplained/oil-and-petroleum-products/#:~:text=Over%20millions%20of%20years%2C%20the,or%20oil%20from%20the%20earth.
Valco. “PTA – Manufacturing process of PTA (Terephthalic acid).” https://www.valcogroup-valves.com/faq-2/pta-terephthalic-acid-manufacturing-process-of-pta/
Industrial Quick Search. “Epoxy Adhesives.” https://www.iqsdirectory.com/articles/adhesive/epoxy-adhesives.html#:~:text=Epoxy%3A%20Epoxy%20glue%20is%20a,on%20a%20surface%20or%20object.
Science Direct. “Synthetic Resin.” https://www.sciencedirect.com/topics/chemical-engineering/synthetic-resin#:~:text=Synthetic%20resin%20is%20a%20chemical,the%20main%20component%20in%20plastic.
Valco. “Epoxy resins – Manufacturing process of Epoxy.” https://www.valcogroup-valves.com/faq-2/epoxy-resins-manufacturing-process-of-epoxy-resins/
Kohlstedt, Kurt. “End of the Road for Botts'’ Dots: Round Markers Being Phased Out in California.” 99 Percent Invisible. https://99percentinvisible.org/article/end-road-Botts'-dots-round-markers-phased-california/
Conserve Energy Future. “Is Resin Recyclable? (And How to Dispose of it?).” https://www.conserve-energy-future.com/is-resin-recyclable.php
National Library of Medicine. “Towards Sustainable Recycling of Epoxy-Based Polymers: Approaches and Challenges of Epoxy Biodegradation.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10305103/
Petcore. “How does PET plastic recycling work?.” https://www.recycletheone.com/recycle-now/how-does-pet-plastic-recycling-work/
Mold Plastic Injection. “What Is Polyester & Polyester Injection Molding ester Thermoplastics” https://www.moldplasticinjection.com/polyester-plastic-injection-molding
Science Direct. “Resin Transfer Molding.” https://www.sciencedirect.com/topics/materials-science/resin-transfer-molding#:~:text=The%20RTM%20process%20involves%20hand,until%20the%20resin%20is%20cured .
Union Pacific. “Transportation: Delivering the Plastic Products You Can’t Live Without.” https://www.up.com/customers/track-record/tr020420-transportation-and-plastics.htm#:~:text=Oftentimes%2C%20plastic%20pellets%20are%20bagged,ocean%20carrier%2C%20and%20shipped%20overseas.
Hotmelt. “Adhesive Academy: Epoxy Explained.”
Trocellen. “Can the PE foam have different colors?” https://trocellen.com/can-pe-foam-different-colors/#:~:text=Polyethylene%20is%20basically%20translucent%20or,help%20improving%20usability%20and%20quality.
SpecialChem. “Pigments for Plastics: Complete Technical Guide.” https://polymer-additives.specialchem.com/selection-guide/pigments-for-plastics#:~:text=Pigments%20are%20organic%20or%20inorganic,specific%20need%20can%20be%20tricky.
ScienceDirect. “Anthraquinone.” https://www.sciencedirect.com/topics/chemistry/anthraquinone#:~:text=Anthraquinones%20(polyketides%20compounds)%20are%20an,used%20in%20herbal%20slimming%20diets.
S&K Packaging. “The Ultimate Guide to Polypropylene Bags.” https://sandkpackaging.com/the-ultimate-guide-to-polypropylene-bags/#:~:text=The%20weaving%20machines%20create%20large,to%20printing%20and%20more%20durable.
Mitsubishi Chemical Corporation. “Mitsubishi Chemical Bisphenol-A Technology.” https://www.m-chemical.co.jp/en/petrochem-license/technologies/pdf/Introduction_MCC_BPA_Process.pdf
ACS Publications. “Technoeconomic Analysis of the Production of Epichlorohydrin from Glycerol.” https://pubs.acs.org/doi/10.1021/acs.iecr.5b02555#:~:text=This%20process%20consists%20of%20the,an%20alkali%20to%20obtain%20epichlorohydrin.
Wikipedia. “Epoxy.” https://en.wikipedia.org/wiki/Epoxy#:~:text=The%20most%20common%20epoxy%20resins,known%20as%20BADGE%20or%20DGEBA).
Codefine. “How To Recycle Polypropylene Bags.” https://codefine.com/blog/how-to-recycle-polypropylene-bags/#:~:text=However%2C%20recycling%20PP%20bags%20is,it's%20ready%20for%20further%20processing.
The Roden Group. “Plastic Molding 101: Understanding Types, Properties, and Applications.” https://www.rodongroup.com/blog/plastic-injection-molding-101-the-types#:~:text=In%20plastic%20injection%20molding%2C%20raw,profile%20for%20the%20end%20product .
Embodied Energy sources:
Market Research Reports. “World’s Top Epoxy Resin Manufacturers.” https://www.marketresearchreports.com/blog/2018/12/28/world%E2%80%99s-top-epoxy-resin-manufacturers#:~:text=Asia%20Pacific%20is%20major%20production,65%25%20of%20total%20production%20market.
Our World in Data. “Energy Mix.” https://ourworldindata.org/energy-mix
Statista. “Polyethylene terephthalate (PET) production capacity distribution worldwide in 2017, by region.” https://www.statista.com/statistics/720231/global-polyethylene-terephthalate-production-capacity-distribution-by-region/
ACS Publications. “Energy and Air Emissions Embodied in China−U.S. Trade: Eastbound Assessment Using Adjusted Bilateral Trade Data.” https://pubs.acs.org/doi/full/10.1021/es803142v
Sustainability Impact Metrics. “Electricity in LCA ”https://www.ecocostsvalue.com/lca/electricity-in-lca/
Ashby, Michael F.. “Chapter 6 Eco-Data: 6.5 Eco-properties.” Materials and the Environment.
Ashby, Michael F.. “Chapter 15 Material Profiles.” Materials and the Environment.
ScienceDirect. “Anthraquinone.” https://www.sciencedirect.com/topics/chemistry/anthraquinone#:~:text=Anthraquinones%20(polyketides%20compounds)%20are%20an,used%20in%20herbal%20slimming%20diets.
Waste and Pollution sources:
Ecology Center. “PTF: ENVIRONMENTAL IMPACTS.’ https://ecologycenter.org/plastics/ptf/report3/#:~:text=Manufacturing%20PET%20resin%20generates%20more,size%20bottle%20out%20of%20glass.
Unites States Environmental Protection Agency. “Epoxy Resins Production and Non-Nylon Polyamides: National Emission Standards for Hazardous Air Pollutants (NESHAP).” https://www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-and-non-nylon-polyamides-national-emission
Massachusetts Institute of Technology. “An Environmental Analysis of Injection Molding.” https://web.mit.edu/ebm/www/Publications/Thiriez_ISEE_2006.pdf
Essentra Components. “Is injection moulding environmentally friendly?” https://www.essentracomponents.com/en-gb/news/manufacturing/injection-moulding/is-injection-moulding-environmentally-friendly
Codefine. “How To Recycle Polypropylene Bags.” https://codefine.com/blog/how-to-recycle-polypropylene-bags/#:~:text=However%2C%20recycling%20PP%20bags%20is,it's%20ready%20for%20further%20processing.
Scielo. “Degradation of terephthalic acid by a newly isolated strain of Arthrobacter sp.0574.” http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000400020#:~:text=Terephthalic%20acid%20is%20an%20important,methods%20are%20complex%20and%20expensive.
Science Direct. “Epichlorohydrin.” https://www.sciencedirect.com/topics/nursing-and-health-professions/epichlorohydrin#:~:text=Epichlorohydrin%20can%20also%20be%20lost,soils%20and%20other%20solid%20surfaces.
United States Environmental Protection Agency. “LOCATING AND ESTIMATING AIR
EMISSIONS FROM SOURCES OF EPICHLOROHYDRIN.” https://www.epa.gov/sites/default/files/2020-11/documents/epichlorohydrin.pdf
National Library of Medicine (NLM). “Evaluating the Effects of Air Pollution from a Plastic Recycling Facility on the Health of Nearby Residents.” https://pubmed.ncbi.nlm.nih.gov/28655940/
Diamond Hardness Tester. “REDUCING ENVIRONMENTAL IMPACT: PLASTIC INJECTION MOLDING..” https://www.hardnessgauge.com/reducing-environmental-impact-plastic-injection-molding%EF%BF%BC/#:~:text=and%20disposal%20processes.-,Air%20Pollution,harmful%20gasses%20into%20the%20environment.
Carbon Care. “CO2 Emissions Calculator.” https://www.carboncare.org/en/co2-emissions-calculator
Venture Wells. “measuring sustainability.” https://venturewell.org/tools_for_design/measuring-sustainability/life-cycle-assessment-content/