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Egg – Carton Redesign
ENGS 171 Final Project
May 28, 2008
G. Owen Cadwalader G. Owen Cadwalader G. Owen Cadwalader G. Owen Cadwalader PrabPrabPrabPrabhu Perumalsamyhu Perumalsamyhu Perumalsamyhu Perumalsamy Shreyan PoudyalShreyan PoudyalShreyan PoudyalShreyan Poudyal Akash ShahAkash ShahAkash ShahAkash Shah
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Table of Contents Index of Tables ................................................................................................................... 2 Table of Figures .................................................................................................................. 3 Introduction......................................................................................................................... 4 Life Cycle Assessments (LCAs)......................................................................................... 5
Boundaries ...................................................................................................................... 5 Methodology................................................................................................................... 5
LCA – Polystyrene...................................................................................................... 6 LCA - Paper ................................................................................................................ 9 LCA - Polyethylene .................................................................................................. 12
Summary of Environmental Impacts ............................................................................ 15 Per Carton Impact ..................................................................................................... 15 Overall Impact .......................................................................................................... 15
Possible Solutions ............................................................................................................. 15 Our Solution...................................................................................................................... 17
Egg-Carton Redesign .................................................................................................... 17 Solution Pathway #1: The Personal Reusable Egg-Carton....................................... 21 Solution Pathway #2: The McNamara Dairy Model ................................................ 22
Survey and Results........................................................................................................ 23 Process Flow ................................................................................................................. 24 Stella Model .................................................................................................................. 26
Discussion and Results of Model.............................................................................. 26 LCA: Two Different Levels of Ecological Design ....................................................... 29
Conclusion ........................................................................................................................ 32 Works Cited ...................................................................................................................... 33
Index of Tables Table 1: Polystyrene LCA per carton based on Conventional Air Pollutants .................... 7 Table 2: Polystyrene LCA per carton based on Greenhouse Gas Emissions ..................... 7 Table 3: Polystyrene LCA per carton based on Energy Consumption ............................... 7 Table 5: Paper LCA per carton based on Greenhouse Gas Emissions ............................. 10 Table 6: Paper LCA per carton based on Energy Consumption....................................... 10 Table 7: Polyethylene LCA per carton based on Conventional Air Pollutants ................ 12 Table 8: Polyethylene LCA per carton based on Greenhouse Gas Emissions ................. 13 Table 9: Polyethylene LCA per carton based on Energy Consumption ........................... 13 Table 10: Per Carton Impacts of Each Material................................................................ 15 Table 11: Overall Total Impacts of Each Material (Relative to Use) ............................... 15 Table 12: Stella Model Results – Reservoirs and Flows .................................................. 29 Table 13: Comparison of Overall Impacts........................................................................ 32
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Table of Figures Figure 1: Polystyrene Energy Use Breakdown by Sector................................................... 8 Figure 2: Polystyrene CO2 Emissions Breakdown by Sector ............................................. 8 Figure 3: Paper Energy Use Breakdown by Sector .......................................................... 11 Figure 4: Paper CO2 Emissions Breakdown by Sector ..................................................... 11 Figure 5: Polyethylene Energy Use Breakdown by Sector............................................... 14 Figure 6: Polyethylene CO2 Emissions Breakdown by Sector ......................................... 14 Figure 7: DfE Pollution Prevention Hierarchy of Possible Solutions............................... 16 Figure 8: Reusable Carton Design .................................................................................... 17 Figure 9: Closed Carton with View of Snap Closures...................................................... 18 Figure 10: Stamped Information....................................................................................... 19 Figure 11: Stackable Cartons............................................................................................ 20 Figure 12: Side View of Open Container ......................................................................... 20 Figure 13: Wide Open View of Carton and Clear Cover.................................................. 21 Figure 14: Survey Results................................................................................................. 24 Figure 15: Process Flow of Egg-Cartons According to Our Proposed Solution .............. 25 Figure 16: Stella Model of Our Proposed Solution .......................................................... 26 Figure 17: Stella Model Results – Reservoirs................................................................... 28 Figure 18: Stella Model Results – Flows.......................................................................... 28 Figure 19: Comparative Study of Conventional Air Pollutants........................................ 30 Figure 20: Comparative Study of CO2 Emissions ............................................................ 31 Figure 21: Comparative Study of Total Energy Used ...................................................... 31
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Introduction
This project aims to assess the environmental impact of the polyethylene, paper,
and polystyrene foam based egg cartons used by the food markets and consumers and
provide a conclusive solution that will reduce the impacts of these egg cartons. The
project consists of three stages – life cycle assessment (LCA) of each packaging material,
comparative study of their impacts, and a solution to reduce the environmental impacts of
egg cartons.
The use of plastics and polystyrene foam has been on the rise and has been used
to pack food, store it and prevent it from contamination. Egg cartons typically available
in the markets are made up of reclaimed (pre-consumer recycled) paper, clear plastic, and
polystyrene foam. We have performed life cycle assessments for each of type of carton to
evaluate the energy consumption, end-of-life, and emissions from each carton. Our
process was based loosely on a previous European study of egg cartons (Zabaniotou and
Kassidi 549-559). To obtain total environmental impact on a national scale, we used the
average number of shell eggs consumed per person in the US.
To reduce the environmental impact of egg cartons we chose to redesign the egg
carton and the system of distribution from the deepest ecology that we could without
drastically changing human choices. We designed a polyethylene reusable egg carton that
will be returned to the producer after the consumer has used it. The carton will then be
washed, re-packed with eggs, and returned to the store. We used Stella to model the flow
of cartons from the producer to the store to the consumer and back in order to determine
the number of reusable cartons that must be produced each year. We created a design for
a reusable polyethylene egg carton in Solid Works that will be three times the thickness
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of the currently available disposable egg cartons. Using this system the environmental
impact of egg cartons in the US will be reduced by ~2/3 in terms of energy use, green
house gas emissions, and air pollutants.
Life Cycle Assessments (LCAs)
Boundaries
We have evaluated the life cycle of each of the three materials that egg cartons are
made from: polystyrene foam, paper, and polyethylene. The boundaries of the life cycle
we have evaluated are quite broad. We have taken into account everything from the
cradle (material mining or collection), through the manufacturing of the product, and to
the grave (the effects of disposal on the environment.) This broad life cycle gives us the
ability to truly assess an egg carton’s impact on the environment from the beginning of its
manufacturing process to its disposal.
Methodology Our method for life cycle assessment involved using the Carnegie Mellon University
Green Design Institute’s life cycle assessment website ("Economic Input-Output Life
Cycle Assessment (EIO-LCA)."). Here, we were able to assess the impact of a certain
material from the cradle to the grave. We looked at impacts of greenhouse gas emissions,
energy, toxic releases, and conventional air pollutants. All were quantified on a monetary
basis; meaning for $1 million dollars of a material the impact in each sector is shown. We
then converted $1 million dollars of material to impact per carton by finding the
wholesale price of each egg carton ("Egg Cartons at a Discount, Egg Trays, Egg Boxes,
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Poultry Supplies, Incubators, Waterers, and Feeders."). Finally we found the average
number of shell eggs consumed by an American ("President's Council on Food Safety --
Egg Safety, From Production to Consumption: An Action Plan to Eliminate Salmonella
Enteritidis Illnesses Due to Eggs."), estimated the number of cartons of each type by
finding the ratio at Shaw’s food store, and determined total impact of each carton type.
Americans eat an average of 234 eggs per years and 70% of those are shell eggs,
which are sold in cartons. If each container holds a dozen eggs, approximately 4.1 billion
egg cartons are sold each year in the United States. From a survey at Shaw’s in West
Lebanon, we found that 52% of the cartons were paper, 40% were polyethylene, and 8%
were polystyrene. We believe that the stock of eggs at Shaw’s is a good representation of
the ratio of different eggs cartons sold in the United States.
LCA – Polystyrene The environmental impacts of polystyrene foam are listed in following tables. Power
generation and supply during manufacturing creates the largest impact by far for
conventional air pollution, greenhouse gas emissions, and energy. The largest impact for
toxic releases is foam product manufacturing. Since the major impacts come from the
manufacturing process any reduction in manufacturing would be environmentally
beneficial.
Conventional Air Pollutants SO2 CO NOx VOC Lead PM10 g/carton g/carton g/carton g/carton g/carton g/carton Total for all sectors 0.392 1.597 0.376 0.372 0.000 0.074 Power generation and supply 0.293 0.014 0.132 0.001 0.000 0.006 Petrochemical manufacturing 0.017 0.005 0.013 0.041 0.000 0.001 Petroleum refineries 0.011 0.006 0.003 0.009 0.000 0.001 Oil and gas extraction 0.009 0.016 0.007 0.011 0.000 0.000 Other basic inorganic chemical manufacturing 0.008 0.001 0.001 0.000 0.000 0.000 Synthetic dye and pigment 0.004 0.007 0.000 0.001 0.000 0.000
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manufacturing Other miscellaneous chemical product manufacturing 0.004 0.000 0.004 0.001 0.000 0.000 Support activities for oil and gas operations 0.004 0.003 0.002 0.001 0.000 0.001 Truck transportation 0.003 0.926 0.067 0.069 0.000 0.002
Rail transportation 0.003 0.006 0.051 0.002 0.000 0.001
Table 1: Polystyrene LCA per carton based on Conventional Air Pollutants ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
Table 2: Polystyrene LCA per carton based on Greenhouse Gas Emissions ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
Energy Total Electricity Coal Natural Gas LPG MJ/carton MJ/carton MJ/carton MJ/carton MJ/carton Total for all sectors 2.282 0.442 0.610 1.051 0.121 Power generation and supply 0.638 0.000 0.505 0.113 0.000 Other basic organic chemical manufacturing 0.199 0.045 0.031 0.141 0.009 Plastics material and resin manufacturing 0.186 0.037 0.012 0.150 0.009 Foam product manufacturing 0.136 0.152 0.000 0.048 0.009 Petroleum refineries 0.127 0.008 0.000 0.061 0.057 Truck transportation 0.094 0.001 0.000 0.002 0.000
Table 3: Polystyrene LCA per carton based on Energy Consumption ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
Green House Gases GWP CO2 CH4 N2O CFCs g/carton g/carton g/carton g/carton g/carton Total for all sectors 183.885 148.395 19.013 12.363 4.037 Power generation and supply 53.820 53.235 0.000 0.000 0.647 Other basic organic chemical manufacturing 16.107 11.076 0.000 5.031 0.000 Truck transportation 13.124 12.929 0.020 0.180 0.000 Plastics material and resin manufacturing 9.360 9.360 0.000 0.000 0.000 Oil and gas extraction 8.853 1.486 7.371 0.000 0.000 Waste management and remediation services 7.137 1.129 6.006 0.009 0.000 Petroleum refineries 6.806 6.767 0.038 0.000 0.000 Foam product manufacturing 5.012 5.012 0.000 0.000 0.000 Grain farming 4.368 0.380 0.176 3.803 0.000 Petrochemical manufacturing 4.329 4.329 0.000 0.000 0.000
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Energy Use (Total: 692 TJ/year in US)
Power generation and supply
Other basic organic chemicalmanufacturing
Plastics material and resin manufacturing
Foam product manufacturing
Petroleum refineries
Truck transportation
Other
Figure 1: Polystyrene Energy Use Breakdown by Sector
CO2 Emissions (Total: 55,800 MT of CO2 Equivalent/year in
the US)
Power generation and supply
Other basic organic chemicalmanufacturing
Truck transportation
Plastics material and resinmanufacturing
Oil and gas extraction
Other
Figure 2: Polystyrene CO2 Emissions Breakdown by Sector
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LCA - Paper From the Life Cycle Assessment for paper containers, we can see that a major
portion of the impact is due to Paper and Paperboard Mills and Power Generation
activities. Per year, according to our estimates, more than 2 billion paper cartons are sold.
The major portion of the impact caused by paper cartons is in terms of greenhouse gas
emissions, energy consumption, and toxic release is due to Paper and Paperboard Mills.
The principal agent for conventional air pollutants is Power Generation. In addition,
Truck Transportation contributed a lot of the CO and Nitrous Oxide emissions per year.
The totals for each sector were as follows, for a year:
Conventional Air Pollutants: 3884 MT/year of Carbon monoxide
Greenhouse Gases: 364,553 MT/year of Carbon dioxide
Energy: 5383 TJ/year Total Energy Consumed
Toxic Releases: 388 MT/year Total Released into the Air
The impacts caused by each carton are shown in the following tables for the three major
sectors:
CONVENTIONAL AIR POLLUTANTS SO2 mt CO mt NOx mt VOC mt Lead mt PM10 mt (g/carton) (g/carton) (g/carton) (g/carton) (g/carton) (g/carton) Total for all sectors 0.411 1.824 0.390 0.258 0.000 0.155 Power generation and supply 0.267 0.013 0.121 0.001 0.000 0.006 Paperboard container manufacturing 0.061 0.000 0.001 0.000 0.000 0.000 Paper and paperboard mills 0.028 0.187 0.039 0.015 0.000 0.021 Adhesive manufacturing 0.006 0.002 0.003 0.000 0.000 0.000 Synthetic dye and pigment manufacturing 0.004 0.008 0.000 0.001 0.000 0.000 Other basic inorganic chemical manufacturing 0.004 0.000 0.000 0.000 0.000 0.000 Oil and gas extraction 0.004 0.007 0.003 0.005 0.000 0.000
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CONVENTIONAL AIR POLLUTANTS Continued SO2 mt CO mt NOx mt VOC mt Lead mt PM10 mt (g/carton) (g/carton) (g/carton) (g/carton) (g/carton) (g/carton) Petroleum refineries 0.004 0.002 0.001 0.003 0.000 0.000 Truck transportation 0.002 0.796 0.057 0.059 0.000 0.001 Rail transportation 0.002 0.005 0.045 0.002 0.000 0.001 Other 0.027 0.803 0.120 0.171 0.000 0.124
Table 4: Paper LCA per carton based on Conventional Air Pollutants ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
GREENHOUSE GASES
Sector GWP CO2 CH4 N2O CFCs (g/carton) (g/carton) (g/carton) (g/carton) (g/carton)
Total for all sectors 192.000 171.200 13.712 4.304 1.840 Paper and paperboard mills 64.120 64.120 0.000 0.000 0.000 Power generation and supply 49.309 48.716 0.000 0.000 0.593 Paperboard container manufacturing 11.336 11.336 0.000 0.000 0.000 Truck transportation 11.276 11.104 0.017 0.155 0.000 Waste management and remediation services 5.508 0.871 4.631 0.007 0.000 Oil and gas extraction 3.991 0.670 3.321 0.000 0.000 Pulp mills 3.473 3.473 0.000 0.000 0.000 Pipeline transportation 2.702 1.300 1.402 0.000 0.000 Grain farming 2.548 0.222 0.103 2.223 0.000 Coal mining 2.517 0.168 2.349 0.000 0.000
Other 35.220 29.221 1.889 1.919 1.247
Table 5: Paper LCA per carton based on Greenhouse Gas Emissions ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
ENERGY
Sector Total Electricity Coal Natural Gas LPG
(MJ/carton) (MJ/carton) (MJ/carton) (MJ/carton) (MJ/carton) Total for all sectors 2.528 0.118 0.752 1.112 0.053 Paper and paperboard mills 0.991 0.060 0.252 0.508 0.007 Power generation and supply 0.585 0.000 0.463 0.104 0.000 Paperboard container manufacturing 0.236 0.024 0.000 0.146 0.002 Truck transportation 0.081 0.000 0.000 0.002 0.000 Pulp mills 0.069 0.002 0.000 0.054 0.001 Other 0.567 0.031 0.037 0.299 0.043
Table 6: Paper LCA per carton based on Energy Consumption ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
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Energy Consumption Per Year for Total ProductionTotal Number of Cartons: 2.1 Billion
Annual Energy Consumption: 5383 TJ
40%
23%
9%3% 3%
22%
Paper and paperboard mills
Power generation and supply
Paperboard containermanufacturing
Truck transportation
Pulp mills
Other
Figure 3: Paper Energy Use Breakdown by Sector
CO2 Emission per year for Total ProductionTotal Number of Cartons: 2.1 Billion
Annual CO 2 Output: 364553 MT
38%
28%
7%6% 1%
20%
Paper and paperboard mills
Power generation and supply
Paperboard containermanufacturing
Truck transportation
Waste management andremediation services
Other
Figure 4: Paper CO2 Emissions Breakdown by Sector
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LCA - Polyethylene The major impact of polyethylene in terms of air pollutants is from the release of
SO2 and CO from power generation and supply and truck transportation respectively.
0.89 grams per carton of SO2 and released from power generation and supply and 2.33
grams per carton of CO are released from truck transportation. CO2 is the most
significant greenhouse gas emission for the egg carton life-cycle. A total of 359.48 grams
per cartons are released during the life-cycle of each carton. Power generation and supply
is the stage of the life-cycle which emits the most CO2, 161.88 grams per carton, and
plastics material and resin manufacturing and truck transportation are also significant
factors, emitting 35.83 and 32.41 grams per carton respectively. The total energy use per
carton is 5.47 MJ, and the majority of the power is derived from electricity, coal, and
natural gas. Power generation and supply accounts for 1.95 MJ per carton and is the life-
cycle stage, which uses the most power.
Table 7: Polyethylene LCA per carton based on Conventional Air Pollutants ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
CONVENTIONAL AIR POLLUTANTS SO2 CO NOx VOC Lead PM10 Sector (g/carton) (g/carton) (g/carton) (g/carton) (g/carton) (g/carton) Total for all sectors 1.083 3.321 0.901 0.813 0.000 0.115 Power generation and supply 0.889 0.044 0.403 0.004 0.000 0.019 Petrochemical manufacturing 0.040 0.013 0.030 0.095 0.000 0.002 Petroleum refineries 0.021 0.012 0.005 0.017 0.000 0.002 Oil and gas extraction 0.018 0.031 0.014 0.021 0.000 0.001 Plastics bottle manufacturing 0.013 0.000 0.002 0.030 0.000 0.001 Synthetic dye and pigment manufacturing 0.011 0.021 0.001 0.003 0.000 0.001 Other basic inorganic chemical manufacturing 0.009 0.001 0.001 0.000 0.000 0.001 Support activities for oil and gas operations 0.007 0.006 0.004 0.002 0.000 0.001 Truck transportation 0.007 2.326 0.168 0.173 0.000 0.004 Rail transportation 0.006 0.013 0.114 0.005 0.000 0.003
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GREENHOUSE GASES GWP CO2 CH4 N2O CFCs Sector (g/carton) (g/carton) (g/carton) (g/carton) (g/carton) Total for all sectors 414.200 359.480 35.112 11.590 6.764 Power generation and supply 164.160 161.880 0.000 0.000 1.972 Plastics material and resin manufacturing 35.834 35.834 0.000 0.000 0.000 Truck transportation 32.946 32.414 0.050 0.452 0.000 Other basic organic chemical manufacturing 18.544 12.768 0.000 5.776 0.000 Plastics bottle manufacturing 17.480 17.480 0.000 0.000 0.000 Oil and gas extraction 17.404 2.918 14.478 0.000 0.000 Petroleum refineries 12.958 12.882 0.071 0.000 0.000 Waste management and remediation services 10.830 1.714 9.120 0.013 0.000 Petrochemical manufacturing 10.184 10.184 0.000 0.000 0.000 Paper and paperboard mills 8.702 8.702 0.000 0.000 0.000
Table 8: Polyethylene LCA per carton based on Greenhouse Gas Emissions ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
Table 9: Polyethylene LCA per carton based on Energy Consumption ("Economic Input-Output Life Cycle Assessment (EIO-LCA).")
ENERGY
Total Electricity Coal Natural
Gas LPG Sector (MJ/carton) (MJ/carton) (MJ/carton) (MJ/carton) (MJ/carton) Total for all sectors 5.472 1.423 1.748 2.234 0.26 Power generation and supply 1.946 0.000 1.543 0.345 0.00 Plastics material and resin manufacturing 0.711 0.140 0.046 0.574 0.03 Plastics bottle manufacturing 0.589 0.904 0.000 0.166 0.03 Petroleum refineries 0.241 0.016 0.000 0.117 0.11 Truck transportation 0.236 0.003 0.000 0.005 0.00
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Yearly Total Energy (8963 TJ over 1.6B cartons)
36%
13%11%4%
4%
32%
Power generation and supply Plastics material and resin manufacturing
Plastics bottle manufacturing Petroleum refineries
Truck transportation Other
Figure 5: Polyethylene Energy Use Breakdown by Sector
Yearly CO2 (588,826 mt over 1.6B cartons)
44%
10%9%
4%
5%1%
27%
Power generation and supply Plastics material and resin manufacturing
Truck transportation Other basic organic chemical manufacturing
Plastics bottle manufacturing Oil and gas extraction
Other
Figure 6: Polyethylene CO2 Emissions Breakdown by Sector
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Summary of Environmental Impacts
Per Carton Impact
Per Carton Impact SO2 NOx CO2 Total Energy g/carton g/carton g/carton MJ/carton Polystyrene 0.39 0.37 148 2.3 Polyethylene 1.08 0.9 359.5 5.47 Paper 0.41 0.39 171.2 2.5
Table 10: Per Carton Impacts of Each Material
Overall Impact
Total Impact SO2 NOx CO2 Total Energy mt/year mt/year mt/year TJ/year Polystyrene 119 114 45000 692 Polyethylene 1773 1475 588828 8963 Paper 875 831 364553 5383
Table 11: Overall Total Impacts of Each Material (Relative to Use)
Possible Solutions Possible solutions to lower the impacts are listed below from a shallow redesign
to deep ecological redesign:-
1. Switch to all polystyrene foam
2. Redesign disposable egg cartons (less material)
3. Redesign process from store to home
4. Redesign process from distributor to store
5. Design re-usable packaging
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6. Use egg beaters instead of shell eggs
7. Don’t package shell eggs for sale
8. Eat Less Eggs
9. Keep a chicken in each home
10. Don’t eat eggs
The hierarchy of the possible solutions according to DfE criteria is as follows:
Figure 7: DfE Pollution Prevention Hierarchy of Possible Solutions
Not eating eggs, or eating less eggs, and keeping a chicken at home, are
behavioral solutions that we cannot change through product manufacturing. Not
packaging eggs at all is impractical because they will likely break. Eating egg beaters do
Avoidance
Reduction
Re-use
Recycling
Burning
Treatment
Disposal
▪ Don’t eat eggs ▪ Sell unpackaged eggs ▪ Keep a chicken
▪ Eat fewer eggs ▪ Use egg beaters
▪ Design re-usable cartons
▪ Design recyclable cartons
▪ Less Material
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not have the same taste and therefore most people would not choose to eat them.
Therefore we decided to design reusable egg cartons.
Our Solution
Our solution to decrease the impact on the environment involves eliminating
disposable egg cartons. Customers will be able to purchase a reusable egg carton at the
store. This carton, made of recycled material, will be sturdy enough to withstand multiple
uses. There are two distinct ways to do this: one of them is to have personal reusable egg
containers that get refilled at the store by the consumer and the other one is a reusable
egg container that gets refilled at the supplier. Our approaches to these two possible
solution methods are discussed in detail as follows.
Egg-Carton Redesign
Figure 8: Reusable Carton Design
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The reusable carton we have designed will be made of recycled polyethylene, has
overall dimensions of 11.2 in. wide by 3.75 in. deep and 2.5 in. tall, and holds one dozen
eggs. These dimensions are nearly identical to existing egg cartons which will enable the
cartons to be manufactured with existing processes using the same energy per gram as
existing polyethylene cartons. The dimensions also allow consumers to store the cartons
in the existing egg carton shelf in their fridge and stores to stock the same number of
carton on their shelves as before. The weight of the new carton is 140 grams, which is
approximately three times the weight of existing tri-fold polyethylene cartons. The
weight gain is caused by the increased thickness of the carton walls, which will allow it
to be more durable. Because the new reusable carton uses the same material and
manufacturing process as the polyethylene cartons we analyzed previously, our LCA for
the reusable carton is based on ratio of weights of the new carton and existing
polyethylene carton because we assume that the impact per gram of carton will be the
same.
Figure 9: Closed Carton with View of Snap Closures
The reusable carton design presents several advantages over existing
polyethylene, polystyrene, and paper cartons. The new carton is thicker and more
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durable, meaning it can be washed, sterilized, and reused. We estimate that each carton
will undergo 25 reuses in its life-cycle and that most cartons we be discarded due to
staining rather than breakage. The new carton is designed as a bi-fold, with just a top and
a bottom, rather than the more common tri-fold design. The top of the carton is made
from clear polyethylene, which will allow consumers to check for cracked eggs in the
store without having to take the time to open the carton. The bottom may be left clear, or
dyed to differentiate between different egg suppliers or sizes, which will also save the
consumer time in the store. The bottom of each egg cup is also curved to match the top of
the egg carton so that the cartons may be stacked without shifting. This is useful for
transporting the eggs safely and storing them on store shelves.
Figure 10: Stamped Information
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Figure 11: Stackable Cartons
In addition, the top and bottom of the carton are made from the same material,
recycled polyethylene, so they can be recycled together without any sorting at the
recycling plant. All the necessary information, such as supplier name, egg size, and
recycling information are stamped in to the plastic during manufacturing. This means that
the cartons do not require stickers or paper inserts that are currently used in polyethylene
cartons. This saves effort in sorting and removing the paper inserts, and it also means
there are no adhesives that can contaminate a batch in the recycling process.
Figure 12: Side View of Open Container
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Figure 13: Wide Open View of Carton and Clear Cover
Solution Pathway #1: The Personal Reusable Egg-Cart on
The customers will also be able to pick out eggs from a larger crate at the store,
allowing them to ‘choose’ their eggs, much like fruits or vegetables. When the customer
returns to the store for their next purchase, they will bring their egg carton with them, and
be able to purchase eggs without having to buy another carton. If a customer forgets to
bring theirs, they can purchase a new egg carton which can later be returned to the store
for a partial refund.
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To reduce the waste material generated when eggs are transported to the store by
the distributor, larger reusable crates will be designed that will allow egg vendors to
receive eggs in large quantities without having to impact the environment. From our LCA
analysis, we found that a major portion of the impacts were due to truck transportation, so
a method by which we can reduce truck transportation is also desired. By using larger
stackable crates for transportation to the store, there will be a reduction in the number of
trips that trucks will make, which will ultimately decrease the overall CO2 emission.
Solution Pathway #2: The McNamara Dairy Model
Another possible solution is to use reusable egg cartons from the start (i.e. poultry
farmers) and have them distributed to the stores where they can be purchased and later
returned for a refund. The customer will pay a surcharge for pre-packaged egg cartons
each time they buy eggs at the store. When they return the empty cartons at the store
during their next visit, the amount they paid extra will be reimbursed. Much like the glass
milk bottle system implemented by McNamara Dairy which can be returned to the store
for a $1 refund, this will allow us to do away with disposable egg containers and save a
lot of energy use and reduce environmental degradation. This solution will require a
larger number of egg-cartons to be manufactured in the beginning when compared to the
total circulation to account for delays along the route, but, in the long run, it will prove to
be very effective.
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Survey and Results
The implementation of reusable egg containers depends heavily on consumer
behavior and whether or not consumers will be willing to adopt this new system. To
account for consumer behavior, we conducted a survey among Thayer students, staff and
faculty and asked them to pick one out of the following 3 options:
1. Would you prefer to buy your own re-usable egg-carton that you refill by hand at
the grocery store, much like bringing your own shopping bag and picking out
produce?
2. Would you prefer to come to the grocery store pay a deposit and just grab a pre-
packed carton of eggs, then you would return the egg-cartons the next time you go
to the grocery store, much like the McNamara dairy glass bottles?
3. No Preference
Out of 59 responses, 16 people preferred Option 1, 38 preferred Option 2 and 5
people stated no preference over the two. The results of the survey are summarized in the
following chart:
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Survey Results
27%
64%
8%
Option 1: Buy your ownreusable egg container
Option 2: Buy a pre-packagedegg container that can bereturned for a refund
No Preference
Figure 14: Survey Results
From the survey we carried out to assess consumer reaction to our proposed
solution, we found that 64% of our respondents were willing to adopt the second option.
Our new system would have to account for the lag in transport from the store to the
consumer, as well as the time that the egg-cartons will spend in the homes of the
customers before they get returned to the store; and will eventually need to be transported
to the distribution center, cleaned and packaged.
Process Flow
Our proposed system consists of 3 major entities: Supplier, Store and Consumer.
In order for the system to operate, the supplier will provide eggs to the store in pre-
packaged egg-cartons and consumers will buy the eggs from the store. Once they need
another carton or cartons, the consumer will return the empty cartons to the store, which
will send them back to the supplier, where they will get cleaned and re-packaged.
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The following diagram shows the anticipated flow of egg-cartons:
Figure 15: Process Flow of Egg-Cartons According to Our Proposed
Solution
Based on our survey results, it became clear that the consumers would prefer a
system where the egg cartons would come pre-packaged with the type of eggs they
wanted. Initially, when the consumer will come into the store to purchase their eggs, they
will need to pay some deposit for the carton that their eggs came in. The cartons will then
get returned to the store. Returned cartons will then be transported from the store back to
Supplier Store
Consumer
: Full Carton
: Empty Carton
26
the supplier, and will be cleaned, re-packaged and then sent back to the store. We
anticipate that our new carton will be able to withstand an average of 25 uses. However,
there will be certain losses along the way – with some containers getting damaged in
transit, and some containers never being returned by the consumer despite the fact that
they have paid for it. Therefore, there are additional flows to the preceding figure, and a
certain amount of loss associated with both.
In order to account for these different flows, we constructed a model using
Stella® and carried out a simulation for 5 years. The details of the Stella model behavior
are given in the following section.
Stella Model
Figure 16: Stella Model of Our Proposed Solution
Discussion and Results of Model
The purpose of the Stella model is to determine how many eggs cartons are
initially needed in inventory and how many new cartons needed need to be introduced in
to the process flow each month in order to meet consumer demand. Using the fact that
27
each person in the United States eats 234 eggs each year, of which 70% are sold in
cartons, we determined that each American eats about 13.6 cartons of eggs per year, or
about one per month.
The time interval for the model is therefore in months and we broke the carton
supply process into 12 yearly cycles. The goal is to determine initial inventory and new
carton production that will allow the system to meet monthly consumer demand, which is
342 million cartons per month. This value is given to the Sales flow in the model. The
model also assumes that some eggs break or spoil while in the store and that these cartons
are returned directly to the supplier. 2.5% of egg cartons in store inventory are assumed
to be returned each month. Another assumption is that consumers dispose of 10% of the
cartons they buy and return 90%. There are also delays built into the system. Egg cartons
stay in story inventory for two weeks on average and consumers keep purchased cartons
in their homes for six weeks on average before returning them. The final assumption is
that the egg suppliers dispose of 4% of the returned cartons each month, which
corresponds to 25 uses per carton.
The results of the model are shown in the following figures and table. To achieve
the results, we adjusted the initial inventories and new carton flow iteratively until the
system achieved steady state while achieving the goal of delivering 342 million egg
cartons per month to consumers. We found that for the system to function the egg
supplier needs an initial inventory of 513 million cartons and the store needs an initial
inventory of 342 million cartons. This amount is 2.5 times the monthly consumer
demand. To account for prematurely destroyed cartons and disposal after 25 uses, about
30 million new cartons each month need to be produced and introduced in the system.
28
Figure 17: Stella Model Results – Reservoirs
Figure 18: Stella Model Results – Flows
29
Table 12: Stella Model Results – Reservoirs and Flows
LCA: Two Different Levels of Ecological Design
We decided to examine the life cycle of two methods for redesigning egg
containers. The first is switching to 100% polystyrene foam containers, which is the
shallowest ecological redesign and there would be no effort to redesign manufacturing or
production. Production of polystyrene foam egg containers would have to increase more
than 5 fold. The second method is the deepest ecological change based on what the
consumer wanted according to our survey.
As discussed above, the Stella model showed that in a system where a re-usable
container was used 25 times the US would have to produce 30.1 million cartons/month or
361 million cartons/year to satisfy the average yearly consumption of eggs in the US. As
discussed earlier in the current system of disposable containers, the US consumes ~4.1
billion egg cartons a year. These numbers were used to calculate the total emissions of
CO2, NOx, SO2, and the total energy required to produce cartons in a 100% polystyrene
foam system and a polyethylene reusable container system. These were compared to the
total impact of the current system. The data is shown below in the following figures and
tables. The comparisons are amazingly consistent throughout the categories. In all
Months Egg Supplier Store Consumer New Cartons Old Carto ns Return Disposal Sales0 513,000,000 342,000,000 0 30,135,125 0 0 0 663,061,2246 195,799,337 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,600
12 195,799,338 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,60018 195,799,339 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,60024 195,799,341 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,60030 195,799,342 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,60036 195,799,343 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,60042 195,799,344 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,60048 195,799,345 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,60054 195,799,347 176,629,320 501,681,339 30,135,125 13,012,895 325,322,370 17,122,230 342,444,600
Final 195,799,348 176,629,320 501,681,339
30
categories the 100% polystyrene foam system is about 2/3 of the impact as the current
system, and the reusable polyethylene container system is about 1/3 the impact of the
current system.
0
500
1,000
1,500
2,000
2,500
3,000
(mt/yr.)
SO2 (mt/yr) NOx (mt/yr)
Current Disposable Containers
All Polystyrene Foam(disposable)
Polyethelyne (re-usable)
Figure 19: Comparative Study of Conventional Air Pollutants
The preceding figure shows the air pollution impact from the current system of
egg containers, a system using 100% polystyrene foam, and a system of re-usable
polyethylene containers and our reusable container performs better than the other two.
The following figure shows the CO2 greenhouse gas impact from the current
system of egg containers, a system using 100% polystyrene foam, and a system of re-
usable polyethylene containers. Our reusable container does better than the two others
again.
31
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
1,000,000
(mt/yr.)
CO2 (mt/yr)
Current Disposable Containers
All Polystyrene Foam(disposable)
Polyethelyne (re-usable)
Figure 20: Comparative Study of CO2 Emissions
The following figure shows total energy used during the production of the current
system of egg containers, a system using 100% polystyrene foam, and a system of re-
usable polyethylene containers. Again, our reusable container uses less energy when
compared to the other two.
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
(TJ/yr.)
Total Energy (TJ/yr)
Current Disposable Containers
All Polystyrene Foam(disposable)
Polyethelyne (re-usable)
Figure 21: Comparative Study of Total Energy Used
32
The following table shows the environmental impact of the three systems of egg
containers studied. The polyethylene re-usable containers are ~1/3 of the impact of the
current system in all sectors.
Comparison of Overall Impacts
SO2
(mt/yr) NOx
(mt/yr) CO2
(mt/yr) Total Energy
(TJ/yr) Current Disposable Containers 2,767 2,420 998,381 15,038 All Polystyrene Foam (disposable) 1,599 1,517 606,800 9,430 Polyethylene (re-usable) 1,172 976 390,009 5,934
Table 13: Comparison of Overall Impacts
Conclusion We have evaluated the current situation of egg-cartons in the United States and
assessed the environmental impacts associated with their production and use. Upon
looking at our findings, it became clear that a reusable egg-carton was the most
environmentally friendly route to take. We have designed a new egg-carton made of more
sturdy material that will be able to withstand an average of 25 uses and will help to
reduce the environmental impacts of the current system by about 2/3. In addition, we
have also proposed a plan for implementation after carrying out a survey of consumer
preference. Implementation of this new method will be the most important and difficult
part of our proposed solution, as consumer behavior needs to change a lot in order for this
method to be successful. However, through extensive awareness campaigns and other
efforts to inform the consumer of the dangerous impacts that disposable egg-cartons pose
towards the environment, the switch to reusable egg-cartons should be quite smooth and
unproblematic.
33
Works Cited
"Economic Input-Output Life Cycle Assessment (EIO-LCA)." 5/28/2008 <http://www.eiolca.net/use.html>.
"Egg Cartons at a Discount, Egg Trays, Egg Boxes, Poultry Supplies, Incubators, Waterers, and Feeders." 5/28/2008 <http://www.eggcartons.com/>.
"President's Council on Food Safety -- Egg Safety, From Production to Consumption: An Action Plan to Eliminate Salmonella Enteritidis Illnesses Due to Eggs." 5/28/2008 <http://www.foodsafety.gov/~fsg/ceggs.html#intro>.
Zabaniotou, A., and E. Kassidi. "Life Cycle Assessment Applied to Egg Packaging made from Polystyrene and Recycled Paper." Journal of Cleaner Production, 11.5 (2003): 549-59.
