In 2012, approximately 38.2 billion aluminum beverage cans ended up in U.S. landfills, the equivalent of 121 cans for every American man, woman, and child. 1
Seeing giant stacks of soda cans at the grocery market got me thinking about aluminum beverage cans and wondering about their environmental impact. I decided to look into it and share what I found out.
After oxygen and silicon, aluminum is the third most abundant element in the earth’s crust and the most abundant metal. Aluminum is an active metal, meaning it likes to react or combine with other elements so rarely occurs by itself in nature, instead it is found in numerous ores combined with lots of different minerals. Bauxite ore is the most common source of aluminum.
Aluminum is a valuable material.
Aluminum is lightweight, strong, easy to form, corrosion resistive, and infinitely recyclable. It has good reflective and conductivity qualities, is impermeable, and non-combustible.
We may not think about it, but aluminum makes our daily lives possible. A few of the products made with aluminum include cars, airplanes, trains, electronics, lighting, window frames, door frames, siding, bicycles, packaging, and beverage cans.
Aluminum Beverage Can Manufacturing
Let’s begin at the end of the process. This 5-minute video from the Discovery Channel shows aluminum beverage cans being made at dizzying speed.
As you can see, making a seemingly simple aluminum can is not simple. Next, let’s get a glimpse of what’s involved in making aluminum and learn about some of the associated environmental issues.
Bauxite deposits (red from iron oxide) usually occur in horizontal layers close to the surface and are primarily located in tropical and subtropical regions. Much of the world’s bauxite mining is in Australia, China, Brazil, Jamaica, Guinea, and India. The U.S. has small amounts of bauxite in Arkansas, Alabama, and Georgia, however almost all of the bauxite used by U.S. aluminum manufacturers is imported.
Mining ores is a dirty destructive process and bauxite mining is no different.
The majority of bauxite is surface mined. This requires stripping everything off the surface of the land: trees, shrubs, plants, flowers, animals, top soil, and even rocks to expose the bauxite. Giant excavators dig up the bauxite and huge trucks, rail cars, or conveyor systems transport it to a refining plant.
Since bauxite mainly occurs in tropical areas, clearing the land contributes to rainforest deforestation and loss of biodiversity. Bare land does not retain rainfall and causes erosion, sedimentation build up in rivers and streams, drinking water pollution, and farmland degradation.
An ecosystem develops over hundreds, thousands, or even tens of thousands of years. Post-mining attempts at remediation can never replicate or replace what was destroyed.
Bauxite Refining – Bayer Process
The Bayer process invented in 1887 by Carl Josef Bayer is used to extract aluminum-bearing materials from bauxite.
Rock crushing machines grind the bauxite into smaller pieces, which feed into pressurized vessels filled with a hot solution of caustic soda (sodium hydroxide) and lime (calcium oxide). The bauxite dissolves. Insoluble materials are filtered out and pumped into holding reservoirs. The remaining solution is cooled, seeded with crystals to help it solidify, and heated at extremely high temperatures (in excess of 960°C) to remove the remaining water, which is released as steam. The resulting fine white powder, alumina (aluminum oxide), is shipped to aluminum smelters to be made into aluminum.
The filtering process leaves behind a toxic sludge, commonly called red mud or red sludge. Red mud is highly caustic and may contain radioactive materials and heavy metals. The high pH of red mud is strong enough to kill plants, animals, and burn airways if breathed in. Eventually, the red mud dries out, is buried under a layer of soil, and becomes a toxic landfill.
Aluminum Production – Smelting
Smelting is the process of extracting metal by heat and melting. Aluminum is produced using electric current to separate the oxygen from the aluminum in alumina. The Hall-Héroult smelting process invented in 1886 is still in use today.
The alumina is dissolved in a molten (950°C) electrolytic bath within huge rectangular steel containers lined with carbon or graphite called pots. An electric current is passed through the electrolyte and flows between a carbon anode (positive), made of petroleum coke and pitch, and a cathode (negative), formed by the lining of the pot. The carbon anode is consumed during the process and must be replaced.
Molten aluminum is siphoned off and moved to holding furnaces. Sometimes alloys are added but not always, and then it is cast into ingots or made into rolls and shipped off to aluminum product manufacturers.
Aluminum production requires such massive amounts of electricity it’s has been called congealed electricity. It takes 15 kWh of electricity to produce just 1 kilogram (2.2 pounds) of aluminum. That’s enough electricity to power the average American home for half a day or more. Depending on the smelter location, electricity is produced by coal, natural gas, or hydroelectric power plants.
The Bottom Line
Mining and refining bauxite and smelting aluminum is immensely energy intensive, uses large amounts of water, and generates air, water, and soil pollution. Making aluminum is harmful to the environment and the people who live near mining, refining, or smelting operations. Some companies involved in the aluminum industry are working to increase energy efficiency, decrease pollution, remediate mining areas, and reduce impacts to local communities, but making aluminum is not a benign process.
Aluminum is clearly a valuable material with a gigantic environmental footprint and social costs most people don’t see or perhaps even know about. So what can we do?
Let’s go back to the aluminum beverage can. Makers of aluminum drink cans and companies that sell soda, beer, and energy drinks in them tout aluminum’s recyclability, but that deflects attention from the real issue.
The real issue is that it’s wasteful to use a valuable material like aluminum to make a can we open, drink its contents, and then get rid of. Even if we recycle the cans, which Americans only do 54% of the time, recycling still entails transporting, sorting, and smelting the cans, which all use additional energy, water, and resources.
So the next time you’re about to grab a six-pack of beer cans from the store cooler or load a couple of cases of soda cans into your shopping cart, stop, think about it, and then walk on by.
If you do buy that six-pack or case, make sure you recycle the cans!
- Every Day Should Be America Recycles Day
- Living Downstream – Book Review
- Love Canal – Book Review
- Reduce Comes Before Recycling
- Silent Spring – Book Review
- These figures were calculated using an estimated average can weight of 0.5 ounces, data from the U.S. EPA Municipal Solid Waste Generation, Recycling, and Disposal Tables and Figures for 2012 report, and U.S. Census Bureau 2012 U.S. population statistics.
- Alcoa – Aluminum smelting
- Discovery Channel – How it’s made – Aluminum cans (video embedded above)
- Friends of the Earth Europe – The Forest Turns to Dust (video about aluminum’s social cost)
- Hydro – Aluminum, environment and society
- Mexus Education – The Making of Aluminum (video)
- The Sydney Morning Herald – Toxic red mud swamps villages in Hungary, October 6, 2010
- U.S. Energy Information Administration – How much electricity does an American home use?
- U.S. EPA – Aluminum Production Wastes
- Wikipedia – Aluminum
- Wikipedia – Bauxite
- Wikipedia – Red Mud