Environmental Costs of Linear Societies October 9, 2006.
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Transcript of Environmental Costs of Linear Societies October 9, 2006.
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Environmental Costs of Linear Societies
October 9, 2006
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Life Cycle Analysis of Aluminum Cans
• Americans use 102.2 BILLION aluminum cans/ year (368 per capita/year)
• We throw away 49.6% of these cans (50.7 billion!)
• Biggest environmental impact of this disposal is “upstream” from the consumer
• Had these cans been recycled enough energy would have been saved to supply gasoline to over 1 million cars for an entire year
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Aluminum Can Production: Step 1 – Bauxite Mining
• Most bauxite “ore” from open pit or strip mines in Australia, Jamaica and Brazil (99% of US needs is imported)
• Bauxite mining results in land clearance, acid mine drainage, pollution of streams and erosion
• 5 tons of mine “tailings” (waste) produced per ton of bauxite ore removed
• Significant fossil fuel energy consumed in mining and transporting bauxite ore
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Land Degradation from mining
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For each ton of useful ore extracted, many tons of “over-burden” have to be removed in the process. For bauxite ore, the ratio can be as high as 5:1.
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Mineral ores and metals are shipped all over the world, consuming vast quantities of energy in the process.
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Aluminum Can Production: Step 2 – Alumina Refining
• Bauxite ore is mixed with caustic soda, lime and steam to produce a sodium aluminate slurry
• “Alumina” is extracted from this slurry, purified and shipped to smelters
• Leftover “slag” waste contains a variety of toxic minerals and chemical compounds
• Alumina refining process is also fossil fuel energy intensive
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Alumina Refining Facilities
Refined alumina
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Aluminum Can Production: Step 3 – Smelting
• Powdered alumina is heated (smelted) in order to form aluminum alloy ingots
• Aluminum smelting uses massive amounts of electricity (usually from coal)
• One ton of aluminum production requires energy equivalent of 5 barrels of oil (210 gallons of gasoline)
• Aluminum smelting also produces 7.4 tons of air pollutants (particulate matter, sulfur oxides, VOCs) for every 1 ton of aluminum produced
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Aluminum Ingots
Aluminum Smelter
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Aluminum Can Production: Step 4 – Tertiary Processing
• Aluminum ingots are melted (requiring more energy) and are extruded as sheets
• Finishing process for rolled sheets involves several chemicals (strong acids and bases) that are toxic
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Aluminum Can Production: Step 5 – Finishing/Assembly
• Aluminum sheet is fed into extrusion tubes and cut into shallow cups
• Cups are fed into ironing press where successive rings redraw and iron the cup. This reduces sidewall thickness, making a full length can
• The bottom is “domed” for strength
• Cans are necked in at the top and flanged to accept the end
• Little chemical pollution at this stage, just electricity use
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Aluminum Can Production: Step 6 – Filling/Distribution
• Cans are shipped without end portion to beverage company
• Beverage is injected under pressure – outward force strengthens the can
• After filling, can is labeled and packaged
• Cardboard and plastic is used, some toxic waste from making paint and ink used for labels
• Finally, product in the can is trucked (diesel fuel use) to a wholesaler/distributor and then to retailer (multiple trips)
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Life Cycle Analysis of an Aluminum Can
• Mining/Extraction of Bauxite – Ship to processing plants• Primary Processing – Convert bauxite to alumina• Secondary Processing – Convert alumina to aluminum
ingots (smelting)• Tertiary Processing – Convert aluminum ingots into
aluminum sheets• Finishing/Assembly – Convert aluminum sheets into
aluminum cans• Filling/Distribution – Fill cans with beverage, transport to
distributor/final consumers• ALL OF THESE STAGES use significant amounts of fossil
fuel energy. MOST OF THESE STAGES generate large quantities of hazardous and toxic waste products
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Aluminum can, used once
Steel can used once
Recycled steel can
Glass drink bottle used once
Recycled aluminum can
Recycled glass drink bottle
Refillable drink bottle, used 10 times
0 8 16 24 32
Energy (thousands of kilocalories)
(65% less energy)
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