Environmental Impact Comparison: PET vs PC Bottle Production

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Environmental Impacts of Producing PET (Polyethylene Terephthalate) Bottles as opposed to PC (Polycarbonate) Bottles

Bilal Arif

National University of Sciences and Technology

Author Note

The author of this paper is Bilal Arif from the Department of Mechatronics Engineering, College of Electrical and Mechanical Engineering at National University of Sciences and Technology and this paper is submitted to Assistant Professor Dr. Danish Hussain of the same department. You

can find the openLCA project file with database and report at the link: http://bit.ly/BilalArif- Project-PETvsPCWaterBottleProduction

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Abstract

This paper presents a green engineering plan for using PET (polyethylene terephthalate) as opposed to the traditional used PC (polycarbonate) for packaged drinking water with a prime focus on the environmental impacts and sustainability. It presents a comprehensive material selection process for choosing the PET bottles, justifying the reasoning for choosing them over the more often used PC bottles. Furthermore, the paper also presents a product life cycle for the PET bottles with a detailed life cycle assessment analysis using life cycle assessment software i.e., openLCA software. With the help of LCA software the environmental impacts of both form of the bottles is analyzed and compared concluding that PET bottles are by far more eco-friendly and are therefore the future of plastic packaging.

Keywords: environmental impact, sustainability, pet, pc, life cycle assessment

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Environmental Impacts of Producing PET (Polyethylene Terephthalate) Bottles as opposed to PC (Polycarbonate) Bottles

Ever since the first human’s mankind has tried to find ways to package food and drinking’s items. In old days people used leather bags for collecting water from ponds or wells but this method was not very hygienic or safe. After that came the glass bottles which though could be hygienic if cleaned properly but they were brittle and could break easily at home or during transport. Today in 21^st century we most commonly use plastic bottles for packaging drinking water, but the question is how safe these plastic bottles really are and what impacts do they have on our environment as in the end of the day plastic is made using fossil fuels which we all know, that it’s burning is raising global temperatures and also adversely harming the

environment.

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Problem Statement

With about 7.7 billion people in the world everyone requires clean drinking water. In several countries the tap water is pure enough to be drinkable but in most countries that is not case. For those countries people most commonly use filtration plants for getting clean water but it has been reported that filtration plant water is also not hundred percent safe for drinking as the question about filtration plants is that how safe the filtration process really is. In several cases the filtration process may be up to the purification standards and would also be maintained regularly for changing the filters and purifying the cleaning process but in most cases such as that in the developing countries that is highly unlikely. In underdeveloped countries the conditions are worse. Therefore, most commonly people prefer using drinking water bottles for daily uses.

About 50 billion plastic bottles are used to consume drinking water every year around the world.

These drinking bottles are mostly made of plastic which is produced by highly purifying crude oil or natural gases. Burning crude oil and purifying it has adverse effects for the environment with emissions of toxic gases in the environment causing not just pollution but also causing the global temperatures to rise. It has already been reported how our climate has changed over the past few decades and how this will continue to be the case unless and until our production process change. As much as it is important for changing the production processes it is also important to change the material selection process and explore new materials to find the most environment friendly material for the production of plastic bottles.

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Solution – Using PET Bottles as compared to PC Bottles

PET stands for polyethylene terephthalate, which is a strong, clear, inert, light weight, reusable plastic belonging to the polyester family. It is typically called "polyester" when used for fibers or fabrics. It is made from ethylene glycol and terephthalic acid which are combined at high temperatures and low vacuum pressure forming long chains of polymers. While PC stands for polycarbonate, which is a thermoplastic and a high performance tough, amorphous polymer with organic functional groups linked to carbon chain. The reason for choosing PET over PC is that PET is a very inert material that is resistant to attack by micro-organisms and does not react with food products while PC which contains Bisphenol-A (BPA) compound has been reported to leak trace amounts of BPA into the foods and beverages. In tests on lab animals, it had been seen that, BPA appears to copy or disturb the hormone estrogen and affect the reproductive system.

This could possibly raise the risk for cancer. BPA has also been linked with cardiovascular disease and diabetes in humans. Therefore, Canada banned the use of BPA in polycarbonate baby bottles in 2008 and European Union in 2011. Another major reason for using PET bottles over PC bottles is that PET bottles can be recycled about 2-3 times before they need to be discarded while PC bottles can only be recycled once. The environmental impacts for life the cycle of PET bottles are also less than the PC bottles which will be shown in detail in the “Environmental impacts of using PET Bottles as compared to the PC Bottles” heading using life cycle assessment.

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Material Selection Process for PET Bottles

For making plastic bottles for storing water, we need a form of plastic which is tough, clear, has a good strength, is flexible to some extent and is also resistant to microorganisms.

Polyethylene terephthalate has an elastic modulus of 3.5 to 11 GPa and a flexural modulus of 8.3 GPa to 14 GPa while Polycarbonate has an elastic modulus of 2.2 GPa and a flexural modulus of 2.3 GPa to 10 GPa. This shows that PET bottles are more flexible than PC bottles which will thus help in the transport and utility of the bottles. PET also has a good yield strength of around 40 MPa and a tensile strength of around 170 MPa while PC has a tensile of strength of about 55- 75 MPa. Another thing to note is the adverse effects of the material we are using on human health and PET is notably declared to be safe by FDA, Health Canada, the European Food Safety Authority and virtually every other health-safety agency in the world. While PC which is

reported to leach Bisphenol-A (BPA) in the water can cause severe health risks. Though PET is safe but there have been reports that antimony can cause cancer and as PET production uses antimony oxide as a catalyst for making PET therefore there is something to fear but the truth of the matter is that PET contains no toxic amounts of antimony and is thus safe for use and is environment friendly to use as compared to PC bottles. Furthermore, as Polyethylene

terephthalate, Polypropylene and High-density polyethylene which are used to make PET bottles have far less effects on the environment than Polycarbonate, Polybutadiene and Low-density polyethylene which is used to make PC bottles therefore it is best to use PET bottles as compared to PC bottles.

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Manufacturing Process for PET and PC Bottles

We look at the manufacturing process of both the processes to better understand the

“Product Life Cycle” from raw granulates to filled bottles. To produce the PET bottles, we are going to make the plastic bottle using Polyethylene terephthalate (PET), the marketing label on the bottle using Polypropylene (PP) and the lid of the bottle using High-density polyethylene (HDPE). Furthermore, to produce the PC bottles we are going to make the plastic bottle using Polycarbonate (PC), the marketing label on the bottle using Polybutadiene (PB) and the lid of the bottle using Low-density polyethylene (LDPE). Apart from these inputs in our production we will also require electricity, the actual water and transport for transferring the water bottles from the PET or PC granulates production houses to the bottle making factories to the shops. For the purpose of this study, we do not have exact amount of data about the amount of electricity required at each input center so assume that everywhere the electricity consumed will be same and thus neglect in this study for the purpose of comparison between PET and PC bottles. For making the plastic bottles, lids, and the labels we first form granulates of PET, HDPE and PP for PET bottle production and PC, LDPE and PB granulates for PC bottle production. These

granulates are then transferred to a center or factory where the PET or PC preform is made, the labels are made, and the lid is made. Then the perform is blown and the bottle is given its required shape. Finally, the lid and the label are added. Now this plastic bottle is ready to be filled with water, so it is transported at another location where it is filled and then at last the bottle after filling is transported to markets where they are sold. In this study we are not studying how the bottle is then used, recycled by turning the used bottle into flakes and then again

converted into a PET bottle.

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Source: https://www.epa.gov/aboutepa/about-epa-region-4-southeast

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Production of One PET Bottle:

For the production of one PET bottle, we take 60 g polyethylene terephthalate (PET) granulate, 4g polyethylene high density granulate (PE-HD), 1 g polypropylene granulate (PP).

This makes 0.065kg of Granulates (PET, HDPE, PP) which are transported ‘t’ km 0.065 kg*t km and finally the water bottle is filled with 1kg of water.

Production of One PC Bottle:

For the production of one PET bottle, we take 60 g polycarbonate terephthalate (PC) granulate, 4g polyethylene low density granulate (PE-LD), 1 g polybutadiene granulate (PB).

This makes 0.065kg of Granulates (PC, LDPE, PB) which are transported ‘t’ km 0.065 kg*t km and finally the water bottle is filled with 1kg of water.

Life Cycle Assessment of PET and PC Bottles

Introduction

In the following the results of the project “PET vs PC Water Bottle Production” done on the Life Cycle Assessment software “openLCA” are shown.

Project Variants

This table shows the name and description of the variants as defined in the project setup.

Variant Description

PET Polyethylene Terephthalate

PC Polycarbonate

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Selected LCIA Categories

The table below shows the LCIA categories of the selected LCIA method of the project.

Indicator Unit Abiotic depletion ^{kg Sb eq}

Acidification ^{kg SO2 eq} Eutrophication kg PO4--- eq Fresh water aquatic ecotoxicity kg 1,4-DB eq

Global warming (GWP100a) ^{kg CO2 eq} Human toxicity kg 1,4-DB eq Marine aquatic ecotoxicity kg 1,4-DB eq Ozone layer depletion (ODP) kg CFC-11 eq

Photochemical oxidation ^{kg C2H4 eq} Terrestrial ecotoxicity kg 1,4-DB eq

LCIA Results

This table shows the LCIA results of the project variants. Each selected LCIA category is displayed in the rows and the project variants in the columns. The unit is the unit of the LCIA category as defined in the LCIA method.

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Indicator PET PC Unit

1. Abiotic depletion ^1.00420e-9 8.07114e-8 kg Sb eq 2. Acidification ^1.10846e-2 ^1.16466e-2 ^{kg SO2 eq} 3. Eutrophication ^2.38758e-3 2.50228e-3 kg PO4--- eq 4. Fresh water aquatic ecotoxicity ^1.35636e-3 ^2.50665e-3 kg 1,4-DB eq

5. Global warming (GWP100a) ^2.35182e+0 2.63119e+0 kg CO2 eq 6. Human toxicity ^8.28413e-2 ^7.31373e-2 kg 1,4-DB eq 7. Marine aquatic ecotoxicity ^4.46246e+1 ^4.75292e+1 kg 1,4-DB eq 8. Ozone layer depletion (ODP) ^4.33309e-9 ^4.33309e-9 kg CFC-11 eq 9. Photochemical oxidation ^7.91107e-4 ^8.32967e-4 ^{kg C2H4 eq}

10.Terrestrial ecotoxicity 1.41893e-4 1.70977e-3 kg 1,4-DB eq Single Indicator Results

The following charts shows the single results of each project variant for individual indicator.

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• Abiotic Depletion:

• Acidification:

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• Eutrophication:

• Fresh water aquatic ecotoxicity:

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• Global warming (GWP100a):

• Human toxicity:

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• Marine aquatic ecotoxicity:

• Ozone layer depletion (ODP):

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• Photochemical oxidation:

• Terrestrial ecotoxicity:

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Relative Results

The following chart shows the relative indicator results of the respective project variants. For each indicator, the maximum result is set to 100% and the results of the other variants are displayed in relation to this result.

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Environmental Impacts of using PET Bottles as compared to PC Bottles

From the ‘Life Cycle Assessment Results’, it is clear that PET bottles are more environment friendly as they have less environmental impacts than PC bottles when we look at the abiotic depletion of PET as compared to PC or the acidification, eutrophication, freshwater aquatic ecotoxicity, global

warming, marine aquatic ecotoxicity, photochemical oxidation or terrestrial ecotoxicity.

The PET bottles are also sustainable for the environment as they can be recycled about 2-3 times in their life cycle. Approximately 1.5 billion pounds of used PET bottles and containers are recovered in the U.S. each year for recycling, making it the most recycled plastic in America.

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Conclusion

Though PET is much better product of green engineering than PC as it more environment friendly but only about 29.3% of the PET bottles were recycled in 2018 even when they can be recycled 2-3 times in their life cycle. Most of the bottles still end up in landfills and as PET is not biodegradable these bottle stay put in the landfills forever which can prove harmful for the environment someday. The problem with not recycling and using PET is our attitude specifically the way we dispose of the bottles. This may be due to lack of awareness in the consumer but is also because of our lack of care for the environment. With small changes in our lifestyle, we can reuse 100% of PET containers. When compared to its competitors - PET surely comes off as better than its alternative. It leaves less carbon footprint during its manufacturing, is easy to carry, is extremely affordable and when you are conscious enough to recycle, it can beat its contemporaries with its versatility.

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