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Design for the Environment/Disposable Water Bottle

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Introduction

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Disposable Water Bottle has been a widely used commodity in the world. In the last decade, demand of water bottle has experienced significant increases, especially in the developed country such as United States. In 2006, the total global consumption of bottled water was 177.895 billion liters (47 billion gallons), a 61% increases from the 108.088 billions consumed in 2000 [1]. Out of the 177.895 billion liters consumed, United States led the world consumption by consuming 42 billion litters of bottled water (23% of total world consumption) [1].

Due to this major consumption in United States; beginning in 2004, various organizations in the United States has been investigating the effects of water bottle to human life [2]. These organizations mostly focus their analysis on the environmental effects, and health effects that the water bottle might cause. The results of these investigations have yielded several important environmental issues and health issues that should be considered widely.

Two major environmental issues that have been raised are solid waste generation and energy use. Water bottle manufacturers have been producing water bottles that are made of various recyclable but non biodegradable materials [2]. If recycled properly, these water bottles will not cause any pollution to the environment. However in fact, not many of these bottles are actually recycled. In United States alone, 80% of water bottle consumed in 2006 ended in landfills [3], thus generating pollution by introducing solid wastes that are not degradable by the soil.

The energies that are used to produce water bottles are also enormous. According to Pacific Institute, 17 million barrels of oil are used per year to produce the water bottles that are consumed in United States. Combining the energy needed to process and transport the bottles, the number rises up to 50 million barrels of oil [4].

Polyethylene Terephthalate (PET) is the most popular material used for manufacturing plastic bottles and containers in the world. For, example, US plastic container demand is expected to exceed 200 billion units in 2010, consuming nearly 15 billion pounds of plastic resins [5]. PET is commonly implemented for Water bottle because it has good chemical stability, and also a good barrier for moisture and gas [6]. PET water bottle is commonly manufactured through injection moldingand extrusionprocess.

Glassalso has been used lately as an alternative for PET water bottle. Glass is used as the alternative because it provides good chemical stability, transparent, and most importantly, reduce general pollution level. Glass water bottle is manufactured thorough blow moldingprocess. However, care during the manufacturing process are intensively required due to the brittleness of glass.

The latest alternative for Disposable Water Bottle is PLA water bottle.PLA is a new kind of polymer fully synthesized of natural renewable sources such as corn, sugar cane, beet, wheat, and cassava providing the natural sugar as the main source of PLA. Thus, it makes PLA sounds very potential to most people in competing with existing petroleum based polymers especially in food and beverage packaging due to its biodegradability. In 1988 the research on PLA as a new polymer synthesized from Lactic Acid was conducted [7] and in 2001 the demand for lactic acid in market, dominated by food and beverage packaging, was as high as 86,000 ton [8].

Project Information

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Section 2 Group 8
Jonathan Juandi
Wing Cheong Lee
Louis Muliadi
Hans Sutandie

Highlights and Recommendation

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Functional Analysis

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As the baseline technology, PET has been the most commonly used material for water bottle production. The manufacturing process required for the PET production is considerably simple compared with the manufacturing process of the other two alternatives. However, among the 3 alternatives, PET water bottle produces most pollution.

In 2001, PLA water bottle merged to the market as an alternative material for water bottle production. In overall, PLA water bottle produce less pollution compared to the other two alternatives. However, lack of researches and development for the PLA technology hold backs its potential for commercial use.

Glass water bottle has been commercially used in the market as an alternative for PET water bottle; glass water bottle has major advantages over the other two alternatives in terms of its reusability. Aside from its outstanding reusability, glass has a major disadvantage in terms of its manufacturability. Compared with other alternatives, the manufacturing process for glass requires more care. Thus produces more cost.

Streamlined LCA

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In the Premanufacturing stage, glass is considered to be the best alternative for disposable water bottle application. Although virgin materials are used during this stage, glass premanufacturing process produces least residue compared to the other 2 alternatives. Compared with other two alternatives, glass manufacturing requires more complicated and tight controlled process thus requires more energy consumption. Therefore for the manufacturing stage, glass is considered as the worst alternative compared with PET and PLA. Similar to the manufacturing stage, glass is considered to be the worst alternative for the product delivery stage. Glass has the highest density compared with the other 2 alternatives, thus requires most energy during product delivery stage compared with PET and PLA. Glass is the most favorable alternative for the End of Life stage, because glass requires least energy for recycling. Moreover, glass is very reusable compared with the other two alternatives. Therefore, creates less environmental impact. In overall, Glass is considered to be the best solution compared to PLA and PET.

EIOLCA

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According to EIOLCA, glass water bottle production causes more environmental impact compared with PET and PLA. Glass water bottle production creates more air pollution, emits more green house gases, and requires more energy compared to PET and PLA. However, glass water bottle production releases less toxic materials compared to PET and PLA.Therefore, it can be concluded that from the EIOLCA comparison between the 3 alternatives that, PET and PLA are the best solution to be used as the material for water bottle.

Cost Analysis

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Glass water bottle costs the most compared to PET and PLA water bottle. High cost in glass water bottle sector is caused by high manufacturing cost and high transportation cost. Although, glass water bottle costs the most, the difference in the cost between glass and PLA isn't significant.

Recommendation

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From the 4 stage analysis, quantitatively PLA is considered to be the best alternative for the disposable water bottle industry. However, this alternative is not feasible at this point due to lack of information about PLA water bottle processing (eg. Recycling issue of PLA plastic) Due to this holdback, Glass water bottle, which is the 2nd best alternative in overall, is concluded as the best design for today’s condition.

Functional Analysis

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PET, glass and PLA have several advantages and disadvantages that meets our basic function which is a resealable portable water container that is transparent.

PolyEthylene Terephthalate (PET)Water Bottle

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PET bottle have excellent transparency and are extremely lightweight due to the low density. The processing of PET bottle is a lot easier due to good flow when molded allowing high speed manufacturing. It is strong enough for the water container application because it can withstand high internal pressure (5 to 6 bars) while also scratch resistant. As a side note, it is easy to design PET bottle because of the material flexibility and moldabilitiy.

Glass Water Bottle

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Glass bottle have excellent chemical stability and good transparency. Design of glass container is rather challenging after considering its brittleness due to its heavy density therefore weight optimization has to be approached with more caution. Manufacturing method of the glass also has to be tightly controlled to ensure little porosity or to ensure minimal internal stress. To the eyes of the consumer however, glass is perceived to be a premium material, which although is heavier but is firmer and not flimsy. Glass also has outstanding reusability (if the consumer chooses to reuse) of 20 times before health hazard surfaces[9]

PolyLacticAcid (PLA) Water Bottle

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PLA is a new kind of polymer fully synthesized of natural renewable sources such as corn, sugar cane, beet, wheat, and cassava providing the natural sugar as the main source of PLA. This can divert our dependancy on petroleum based plstics hence preserving non renewable sources. From consumers’ perspective, PLA based material is promising in which they posses good properties such as low flammability, high resistance to UV light, lower specific gravity (lighter than other conventional plastics). Despite its advantage of using natural resources thus being environmental friendly, growing corn itself imposes environmental damage coming from the excessive use of pesticides and fertilizers

Economic Input Output Life Cycle Analysis

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Background

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Economic Input-Output Life Cycle Analysis (EIOLCA) model estimates the overall potential environmental impacts over the life cycle/supply chain (pre-manufacturing, manufacturing and operating stage) in the United States with an easier and faster way. The model is US 1997 Industry Benchmark and the economic activity uses $ 1 Million Dollars that means how many dollars of output are required to be produced.

Due to focus on potential environmental impacts of PETbottle manufacturing over the life cycle, options in the category including Conventional Air Pollutants, Greenhouse Gases, Energy and Toxic Releases are chosen to gather desired information.

Conventional Air Pollutants

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EIO-LCA Table - Conventional Air Pollutants

CO

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The highest amount of air pollutant is carbon monoxide (CO) and the main reason is ‘Truck transportation’. Therefore, truck transportation is the first objective to be improved in order to reduce environmental impact.

SO2 and NOx

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Life cycle of glass bottle manufacturing causes significantly high Nitrogen Oxides (NOx) emission which 68.64% produces by glass bottle manufacturing. The reason is that glass manufacturing consumes much more natural gas for fuel (Shown in ‘Energy’ section below). The NOx emission of burning natural gas is much higher than burning Oil [10]. In addition, the main source of SO2 emission is ‘Power generation and supply’ (Shown in the table below) and there is no significant difference in SO2 emission between PET, Glassand PLA.

In contrast, PETand PLAare best choice to be the bottle material in 'Conventional Air Pollutants' section because those manufacturing releases the lowest release of air pollutants.

 
EIO-LCA Table - Conventional Air Pollutants - PET

Green House Gases

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EIO-LCA Table - Greenhouse Gases

The values shown in the chart above are the sum of major greenhouse gases which include carbon dioxide (CO2), methane(CH4), nitrogen dioxide (N2O) and Chlorofluorocarbons(CFCs). This is no significant difference in Life Cycle Processes of PET, Glassand PLAbut it is obvious that glass manufacturing releases almost 14 times amount of greenhouse gases contrasting with plastic manufacturing process. The glassmanufacturing process consumes much more natural gas than plastic and this causes the amount of greenhouse gases is very large. Alternatively, 90% of the hydrocarbon emissions from natural gas are unburned methane[11], considered to be non-reactive in the formation of ozone in the atmosphere and causes large difference in amount.

On the other hand, the greenhouse gases emission of PLAin other life cycle processes is more than PET. Energy used in greenhouse gases emission of PETis less than PLAbecause producing PETresins consumes more energy than grain farming (Shown in the table below).

Therefore, glass manufacturing which releases much more greenhouse gases shows that glass is the worst choice of the bottle material in ‘Greenhouse Gases’ section and PETis slightly better than PLAby comparing the total greenhouse gases emission in the whole life cycle.

 
EIO-LCA Table - Greenhouse Gases - Plastics material and resin manufacturing
 
EIO-LCA Table - Greenhouse Gases - Grain farming & Wet corn milling

Energy

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Rather than considering the output stages in life cycle, input information is also important for further analysis. The data of input is simplified in term of energy and shown in ‘Energy’ section in EIOLCA. The chart above has listed out the total energy used to manufacture water bottle by using PET, Glassand PLAin whole life cycle and three major energy sources (Electricity, Coal and Natural gas). In general, glassbottle manufacturing consumes more energy due to much more energy input in glassmanufacturing process. The main consumer of Coal is power generation and supply which obtains about 90% of the usage of Coal (Shown in the table below). Also, glassmanufacturing consumes much more natural gas than plastic manufacturing. Therefore, PLAbottle manufacturing uses the least energy and is the best choice in ‘Energy’ section.

 
EIO-LCA Table - Energy - PET
 
EIO-LCA Table - Energy - Glass

Toxic Releases

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EIO-LCA Table - Toxic_Releases

After comparing the Toxic Releases Tables of PETand Glass(Shown in the table below), ‘Copper, nickel, lead, and zinc mining’ is the major source of toxic releases in both PETand glassbottle manufacturing including high concentrations of some chemical elements, notably arsenic and sulfuric acid [12]. On the other hand, ‘Plastics material and resin manufacturing’ is the second main source of larger toxic releases. Consequently, more the toxic substance produced and releases in water because of mining, more the toxic substance transferred to Publicly Owned Treatment Works (POTW) which is focused on end-of-pipe solutions to remove wastewater pollutants. Therefore, glassis the best choice of bottle material in ‘Toxic Release’ section.

 
EIO-LCA Table - Toxic Releases - PET
 
EIO-LCA Table - Toxic Releases - Glass

Streamlined Life Cycle Analysis

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Background

Streamlined analysis provides a very fast means to analyze a certain product throughout its life stages. This tool is especially good and useful in conditions where data availability, expense and time are strictly limited.


Below, three streamlined life cycle analyses (SLCA) are presented for bottles made of PET, Glass, and PLA. The analyses are conducted throughout 5 life stages: pre-manufacturing or resource extraction, manufacturing of the bottles, product delivery, product use, and end of life (disposal, recycle, or landfill). Each life stage is evaluated in material choice, energy use, solid residue, liquid residue, and gaseous residue. Each cell of matrix will be assigned a value ranging from 0 (lowest) to 4 (highest) depending on the impact of each component on the environment. Finally, the sum of the scores is calculated and compared to the maximum value (100) to judge the quality of each life cycle.


PolyEthylene Terephthalate (PET) Water Bottle

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Streamlined LCA for PET
Material Choice Energy Use Solid Waste Liquid Waste Gaseous Waste Sum
Pre-Manufacturing 3 3 1 1 1 9
Manufacturing 3 2 4 3 1 13
Delivery 4 3 3 3 2 15
Use 4 4 4 4 4 20
End of Life 4 4 3 4 1 16
Total 18 16 15 15 9 73

Pre-Manufacturing
The lowest score of SLCA of PET lies in this life stage since PET is a petroleum base plastic the main resources of which is non-renewable fossil energy. Furthermore, during this pre-manufacturing stage the amount of residues that are solid, liquid, and gaseous residues is the highest compared with the remaining life stages.

Manufacturing
The main concern in this life stage is the gaseous residues produced from the plant. Other disadvantage is the relatively high amount of energy used generally in the melting process of the resin and in injection of the resin to the mold afterward since high pressure is needed. However, the solid and liquid residues are minimal.

Product Delivery
Since PET is light, the transportation for product delivery is flexible and due to its light weight energy consumption is reduced. However, solid residue (landfill) due to the disposals of truck tires is abundant and gaseous emission from the vehicles combustion is unavoidable.

Product Use
Thanks to lightweight PET, PET based bottles are easy to carry and furthermore they produce no solid, liquid and gas residues during their use.

End of Life
Ninety nine percents (99%) of PET bottles are recyclable in the respective recycling facilities with low energy consumption, solid and liquid residues. However, the gas residue from the transportation to the recycling facility is inescapable thus making it the main concern in this life stage.


Glass Water Bottle

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Streamlined LCA for Glass
Material Choice Energy Use Solid Waste Liquid Waste Gaseous Waste Sum
Pre-Manufacturing 3 2 3 4 3 15
Manufacturing 3 0 3 3 4 13
Delivery 3 2 3 3 3 14
Use 4 4 4 4 4 20
End of Life 4 3 4 4 4 19
Total 17 11 17 18 18 81


Pre-Manufacturing
During this life stage, the main concern is the energy used to transport the raw material to the manufacturing plant. There is only little solid residue mainly from truck or train bodies as the transporting vehicles which can be quickly reused. In addition, raw material transportations also cause gaseous residue.

Manufacturing
the main concern during the manufacture is the extremely high energy input 24/7 needed to melt the raw material. Although, there is only little solid and minimal gaseous residue, water contamination occurs here contributing another concern.

Product Delivery
During the transportation the energy use is very high due to the heavy weight of glass and packaging materials (e.g. boxes) required to compensate for their fragility. Solid residue is of little concern since boxes for example, in particular, are highly recyclable. However, transportations always produce Global Warning Potential (GWP) gas emissions.

Product Use
This life stage scores the highest due to the high reusability and rigidness as well as good appearance that is commonly favoured by consumers. Also, there is no residue at all during the use phase.

End of Life
Since glass bottles are highly recyclable there is very little concern of solid waste. Moreover, in this life stage, liquid and gaseous waste is negligible. Nevertheless, high energy input is required for the recycling process such as proper cleaning and treatment for the bottles.


PolyLacticAcid (PLA) Water Bottle

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Streamlined LCA for PLA
Material Choice Energy Use Solid Waste Liquid Waste Gaseous Waste Sum
Pre-Manufacturing 4 3 3 2 3 15
Manufacturing 3 1 3 4 4 15
Delivery 4 2 3 3 1 13
Use 3 4 4 4 4 19
End of Life 4 1 2 3 2 12
Total 18 11 15 16 14 74


Pre-Manufacturing
The material choice is given the highest score since the resource of PLA is 100% natural and renewable thus the process involves chemical reactions producing abundant liquid residue [13] [14]. During the material extraction, energy use is mainly from coal and natural gas (corn farming) reducing the use of the less abundant oil [15]. Furthermore, the fossil energy input is 50 – 68% lower than that of conventional plastics [16] [17]. Gaseous emission is of interest since in corn farming, CO2 is used for photosynthesis thus helps decrease CO2 concentration in atmosphere. However, the use of excessive pesticides and fertilizers would cause harms to the environment [18].

Manufacturing
The manufacturing of PLA bottles are similar to that of PET since both use the same fabrication methods thus since PLA has lower melting point than PET energy use is reduced but still high amount of energy is required as additional processes such as drying and perform making are needed before resin is injected to the injection molding machine [19] [20] The material used is not completely closed loop but does not involve any restricted material. Also there are no liquid and gaseous residues yet there may be solid residue.

Product Delivery
The transportation vehicles not only emit gaseous residues such as CO and CO2 but also needs abundant fossil fuel input. However, the packaging material which is most commonly cardboard can be recycled which in turn reduces solid waste.

Product Use
In terms of product use, there is nothing in a PLA bottle that can cause any harm to the environment and there is no energy used as well as any residues at all during its use.

End of Life
All PLA bottles are biodegradable but not self biodegradable thus all the bottle must be processed in a composting facility where the temperature must be kept at 1400F for a certain period and this requires high energy use [21]. Also, degradation process produces high amount of gaseous (e.g. CO2) and liquid residues (e.g. water).


Economic Analysis

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Cost of siding with specific alternative must be considered when selecting the best water bottle design for the environment. In order to make useful and non convoluted analysis, assumptions were made to simplify the cost analysis:

  1. Manufacturing plants (for the alternative analyzed) are already in existence and ready to use
  2. Capital cost required to implement the alternatives are neglected
  3. Transportation costs are neglected
  4. The costs are calculated in 1997 USD

The first assumption takes advantage of the fact that current existing manufacturing facilities (for respective materials) can be utilized to produce the water bottle containers. The second assumption is possible because the alternative is expected to be in production for long period, hence capital costs will be minuscule compared to the long term (annual) costs. Transportation are energy and cost intensive but it is neglected because it requires logistics and geological consideration that is beyond the scope of this analysis.

The assumption taken can admittedly boast the image of the certain alternatives. If transportation costs are included, glass implementation costs will likely increase because the heaviness of glass would imply higher transportation cost. Similarly, cost for implementing PLA could be significantly higher due to the capital costs required to implement novel material, not to mention extended research fundings needed.

Please note that indirect costs are excluded because of the lengthy information that is beyond the scope of this analysis.

PolyEthylene Terephthalate (PET)Water Bottle

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Energy Cost PET bottle manufacturing primarily uses blow molding technique. A highly mechanized PET bottle manufacturing could turn a molten plastic into a bottle shaped plastic within 12 seconds [22], which is equal to 300 PET bottles within an hour (assume nonparallel operation). Therefore 12,800,000 cycles are needed to manufacture 3.84 billion bottles in 1997 [23]. One injection machine and one blow molding machine are used to manufacture the PET bottles. Each machine consumes 19kWh = (12,800,000)*(38kWh) = 486 x 10^6kWh and the total energy cost is ($0.05 per kWh)*(486 x 10^6kWh) = 24.3 million

Materials Cost The price of PET resin is 0.947$/kg [24]. Assume weight of PET container is 10 grams (3,840,000,000)*(US$0.947)*(10 gram per bottle) = 36.4 million

Labor Cost Knowing that cost of operating injection and blow molding is $60/hr including labor cost, we assume that our injection molding (with 20 cavities) and blow molding average time will still be 12s to manufacture one PET bottle. Therefore, one hour can produce 6000 PET bottles which equates to 640,000 hours of manufacturing and hence the cost for labor is 76.87 million

In total, it will cost roughly 137.57 million dollars to produce the PET bottles annually.

Glass Water Bottle

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For safety purpose, we choose to manufacture glass bottle that is of transparent non colored shape similar to PET bottle volume. The estimated weight is 250 grams which will ensure some rigidity and allow some safety factor before crack develops.

Energy Cost Assume that for the energy consumed we are burning natural gas. If 1 ton of glass production liberates roughly 700kg of CO2 [25] then we can assume that 255kg worth of methane is being used as the fuel to heat up the glass raw material. Given price of $7 per gigajoule we can assume that to make 1 ton of glass we will require $7 x 255kg / 0.717 x 39 Mjoule = $97 worth of natural gas [26]Using similar bottle numbers as PET, one will require 3,840,000,000 glass which equates to 93 million dollars worth of money being used on energy alone

Materials Cost Now consider that glass is composed of 70% sand and 9% soda ash with the remaining 21% being colorant and smaller particulate. In this analysis, we neglect the remaining 21% because we stated no colorant and the small particulate is really little hence not adding to significant economic value compared to sand and soda ash. Therefore, we say 87% of the bottle mass is sand and 11% of the mass is soda ash. For production of all bottles annually, we need 3.84 billion bottles x 217.5 g = 0.84 million ton of sand, which costs 17.54 million dollars [27]. Similarly for soda ash we require 0.125 million ton of soda ash, which costs 4.37 million dollars [28].

Labor Cost Similar to PET bottles.knowing that cost of running ,blow molding, annealing is $70/hr including labor cost, we assume that our glass cutter (capable of generating 10 gobs per cut) and blow molding average time will still be 15s to manufacture one glass bottle. Therefore, one hour can produce 2400 glass bottles which equates to 1,600,000 hours of manufacturing and hence the cost for labor is 112 million

In total, it will cost roughly 227 million dollars to produce the Glass bottles annually.

PolyLacticAcid (PLA) Water Bottle

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It is assumed that the PLA economic activity would be dominated by Cargill Dow (NatureWorksTM) and the number of PLA production and sales would be based on their established information.

Energy Cost Similar to PET manufacturing, PLA uses injection and blow molding that is highly mechanized in order to reduce downtime. A highly mechanized PET bottle manufacturing could turn a molten plastic into a bottle shaped plastic within 12 seconds, which is equal to 300 PLA bottles within an hour (assume nonparallel operation).Therefore 12,800,000 cycles are needed to manufacture 3.84 billion bottles in 1997. One injection machine and one blow molding machine are used to manufacture the PET bottles. Each machine consumes 19kWh = (12,800,000)*(38kWh) = 486 x 10^6kWh and the total energy cost is ($0.05 per kWh)*(486 x 10^6kWh) = 24.3 million dollars

Materials Cost Assume that price of PLA is $2.3 per kg in 1997 [29]. If the weight of each bottle is 9 grams, then to satisfy 3.84 billion bottles we will require 79.49 million dollars on raw material.

Labor Cost Knowing that cost of operating injection and blow molding is $60/hr including labor cost, we assume that our injection molding (with 20 cavities) and blow molding average time will still be 12s to manufacture one PET bottle. Therefore, one hour can produce 6000 PET bottles which equates to 640,000 hours of manufacturing and hence the cost for labor is 76.87 million

In total, it will cost roughly 180.66 million dollars to produce the PLA bottles annually.

Summary

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Economic Analysis Comparison between Alternatives
PET Glass PLA
Total (million USD) 137.57 227 180.66

References

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  1. ↑ 1.0 1.1 Earth Policy Institute, "Bottled Water Statistics and Data" Available at: http://www.gascape.org/Gas%20Em.html [Accessed:October 2002]
  2. ↑ 2.0 2.1 International Bottled Water Association, “Bottled Water Facts” Available at: http://www.bottledwater.org/public/environment_main.html
  3. ↑ Wikipedia, “Bottled Water Environmental Impacts”, Available at: http://en.wikipedia.org/wiki/Bottled_water#Environmental_impact
  4. ↑ Pacific Institute, “Bottled Water and Energy: A Fact Sheet”, Available at: http://www.pacinst.org/topics/water_and_sustainability/bottled_water/bottled_water_and_energy.html
  5. ↑ 1997 Petroleum Price, Available at: http://www.eia.doe.gov/emeu/international/crude2.html
  6. ↑ Volume of Barrel, Available at: http://en.wikipedia.org/Barrel_(unit)
  7. ↑ Erwin T.H. Vink et al., ”Applications of life cycle assessment to NatureWorksTM polylactide (PLA) production”, Available: Polymer Degradation and Stability, vol. 80, pg. 403 – 419, 2003
  8. ↑ “Biotech Route to Lactic Acid / Polylactic Acid”, Available at: http://nexant.ecnext.com/coms2/gi_0255-130/Biotech-Route-to-Lactic-Acid.html
  9. ↑ The Economics of Refillable Beverage Containers, Institute for Local Self-Reliance “Costs and Benefits of Established Refilling Systems,” March 2008, http://www.grrn.org/beverage/refillables/economic.html
  10. ↑ Gascape, "Home Gas Emissions" Available at: http://www.gascape.org/Gas%20Em.html [Accessed:October 2002]
  11. ↑ Earth Times, "Alternative fuels for pollution reduction" Available at: http://www.sdearthtimes.com/et0198/et0198s4.html [Accessed:January 1998]
  12. ↑ Wikipedia, "Mining" Available at: http://en.wikipedia.org/wiki/Mining [Accessed:January 2008]
  13. ↑ E. D. Ray et al., “Polylactic Acid Technology”, Advanced Material, vol. 12, no. 23. pg. 1841 – 1846, 2000
  14. ↑ H. Nick, “Bio-plastics: Turning Wheat and Potatoes into Plastics”, July, 2007, Available HTTP: http://www.thenakedscientists.com/HTML/articles/article/bioplastics/
  15. ↑ Erwin T.H. Vink et al., ”Applications of life cycle assessment to NatureWorksTM polylactide (PLA) production”, Polymer Degradation and Stability, vol. 80, pg. 403 – 419, 2003
  16. ↑ “Biotech Route to Lactic Acid / Polylactic Acid” [Online Document], May 1, 2002, Available HTTP: http://nexant.ecnext.com/coms2/gi_0255-130/Biotech-Route-to-Lactic-Acid.html
  17. ↑ “Biodegradable Bottle Launched in Canada”, [Online Article], August 13, 2007, Available HTTP: http://www.earthwater.ca/latest-news/p,28/
  18. ↑ B. Melisa et al., “Notes from the Packaging Laboratory: Polylactic Acid – an Exciting New Packaging Material”, [Online Document], Accessed March 2008, Available HTTP: http://edis.ifas.ufl.edu/AE210
  19. ↑ “NatureWorksR PLA ISBM Bottle Guide”, NatureWorksR, [Online Document], 2005, Available HTTP: http://www.natureworksllc.com/product-and-applications/natureworks-polymer/technical-resources/~/media/Product%20and%20Applications/NatureWorks%20Biopolymer/Technical%20Resources/Processing%20Guides/ProcessingGuides_ISBMBottleGuide_pdf.ashx.
  20. ↑ “Injection Stretch Blow Molded Bottles”, NatureWorksR, [Online Article], 2005, Available HTTP: http://www.unicgroup.com/upfiles/file01170656345.pdf
  21. ↑ U. G. Tillman, C. S. Slater Steven, “How Green are Green Plastic?” [Online Article], Scientific American, Aug, 2000, Available HTTP: http://www.mindfully.org/Plastic/Biodegrade/Green-PlasticsAug00.htm
  22. ↑ http://en.wikipedia.org/wiki/Polyethylene_terephthalate
  23. ↑ The Economics of Refillable Beverage Containers, Institute for Local Self-Reliance “Costs and Benefits of Established Refilling Systems,” March 2008, http://www.grrn.org/beverage/refillables/economic.html
  24. ↑ http://www.the-innovation-group.com/ChemProfiles/Polyethylene%20Terephthalate.htm
  25. ↑ http://en.wikipedia.org/wiki/Glass_production
  26. ↑ http://en.wikipedia.org/wiki/Natural_gas
  27. ↑ Kogel, Jessica Elzea, Industrial Minerals & Rocks: Commodities, Markets, and Uses. SME, 2006
  28. ↑ Soda Ash Prices, CSX, “Public Price List CSXT 4012,” February 2008, http://www.csx.com/?fuseaction=customers.min_sand_pricing
  29. ↑ http://www.ptonline.com/articles/200203fa2.html
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