Door to Door: The Magnificent, Maddening, Mysterious World of Transportation (6 page)

There the ore is put through a complex four-step chemical and cooking process, the main feature of which involves dissolving the material with copious amounts of caustic soda. This allows the ore to be separated into two streams, one rich in a precursor compound, aluminum hydroxide, the other, larger stream consisting of a noxious sludge called “red mud,” which is shunted off to giant holding ponds. Red mud is the toxic albatross around the aluminum industry's collective neck, as there is no use or safe disposal method for the stuff.
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Heated to 1,100 degrees and treated with other chemicals in the next stage of manufacturing, the aluminum hydroxide sheds its hydrogen atoms and is converted to aluminum oxide crystals. When washed and dried, the material looks like granulated sugar but is hard enough to scratch glass. Commonly called alumina, these crystals are a little over half aluminum by weight and make for a convenient form for shipping in bulk. Together, alumina and bauxite are one of the most shipped substances on earth, one of what the shipping industry calls the “five major bulks.” (The other four are iron ore, coal, grain, and phosphate rock, most of which is used to make fertilizer, a major U.S. export.)
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This method for refining bauxite was invented by the Austrian chemist Carl Josef Bayer (no relation to the aspirin inventor) in the late 1880s. It proved to be one of two critical discoveries needed to commercialize aluminum production. The Bayer process is still the only practical method for making alumina to this day.

From the refinery, alumina is shipped around the world, with about 10 percent of global supplies diverted for making such products as ceramic insulators, spark plugs, and other dense ceramics, as well as synthetic rubies for lasers and sapphire glass for
watch faces (and, possibly, future smartphones). Alumina is also an ingredient in sunscreens and facial cosmetics. The stuff truly gets around.

Most alumina, however, goes to smelters—some near the refineries, some in the U.S. and across the globe—to be converted from sugary crystals into pure metallic aluminum. This is where the second critical process from the 1880s comes in, essentially unchanged for 130 years.

At the smelter, the alumina is dissolved in a molten mineral called cryolite, which possesses two amazing qualities: it puts the yellow in yellow fireworks, and it cuts the melting point of aluminum to less than half its normal 2,200 degrees, which means it also cuts energy consumption and cost. A synthetic version of cryolite is used these days, as natural supplies previously mined in Greenland have dwindled, and not from an excess of yellow fireworks. The molten mixture of alumina and fake cryolite is then placed in something like a giant battery cell, where it is jolted with fantastic amounts of electrical current via the process of electrolysis. The principles at work should be recognizable to every denizen of a high school chemistry lab who ever used a mild-mannered tabletop version of the process to break down a beaker of water into hydrogen and oxygen with a dry-cell battery and a pair of electrodes. In the same way, the cryolite-alumina mixture, liquefied at 980 degrees, is broken down by industrial-scale electrolysis, which unlocks alumina's chemical bonds joining oxygen to aluminum. The elemental aluminum that can't exist in nature on its own then sinks to the bottom of the molten mixture, a pure metal at last. Then the still liquid aluminum can be drained off, poured into long cylindrical molds, and cooled into ingots. The ingots used to make beverage cans run up to 24 feet long and weigh up to 46,000 pounds each. Each ingot can make 1.5 million 12-ounce cans.

Two different chemists working independently developed the process simultaneously: Charles Martin Hall in Ohio, and Paul Héroult in France. By the time the patents and lawsuits were settled and the smelting method became known as the Hall-Héroult Process,
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Hall had founded a manufacturer he dubbed the Pittsburgh Reduction Company, invented the commercial aluminum industry, and become a billionaire. Later he renamed his outfit the Aluminum Company of America, which is now known as Alcoa.

These two processes from the 1880s are still used to make virtually all the aluminum in the world. Aluminum had only been observed in its pure metallic form a few decades before Bayer, Hall, and Héroult made their discoveries; until they came along, chemists were able to tease out only small amounts of this mysterious metal through laborious and expensive methods. Napoleon III, frustrated when he could not commission enough of the metal for a new generation of lightweight battle armor, settled for some very special aluminum dinner plates he reserved for his most esteemed guests; lesser visitors had to endure eating from far more ordinary (and less expensive) gold and silver. Before the French emperor's time, no one realized that aluminum was a metal at all, nor that it was the third most plentiful element on earth,
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although various medical and textile uses for aluminum-rich compounds have been around since antiquity.
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In 2014, worldwide production of primary aluminum topped 53 million metric tons. Smelting that metal required nearly 690.170 gigawatts of electricity
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—more than twice the power consumption of America's largest and most power-hungry state, California. Aluminum smelting uses more electricity than almost any other industrial process; engineers joke that the metal ought to be defined as “congealed electricity.” Alcoa has located most of its smelting operations near sources of hydropower to lower
the cost and environmental impact, but globally—particularly in China, with more than half the world's production—more aluminum is made with dirty coal-powered electricity than anything else. Domestic aluminum smelting in the U.S. alone consumes 5 percent of the electricity generated nationwide.

What this means is that aluminum's weight advantage over iron comes at a price: iron can be produced from iron oxide in a simple, relatively compact blast furnace; the complex Hall-Héroult process requires literally acres of electrolysis cells and city-scale power plants to produce equivalent amounts of aluminum. The bottom line: a car part made from steel costs 37 percent less than the same part made of aluminum,
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although a life-cycle analysis by the Oak Ridge National Laboratory found that the overall energy and carbon footprint of a mostly aluminum car is less than a standard steel vehicle because of lower operating and fuel costs.
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The calculation changes radically in aluminum's favor when recycled metal is used.

Once cooled, the aluminum ingots from which my seltzer can would be made were shipped out of Australia by cargo vessel to the Port of Long Beach, then taken by rail to Alcoa's Great Smoky Mountains fabrication plant in Tennessee. Ingots made from recycled cans are brought to the same plant. The metal used for cans is not pure aluminum but has small portions of magnesium and manganese (about 1 percent of each) mixed in for strength and stiffness, with the tops given an extra portion of magnesium and less manganese so it can withstand the stress of the pop-top. American beverage cans on average are 70 percent recycled metal, 30 percent primary aluminum.
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The Tennessee plant's main product is a five-mile-long coil of sheet aluminum used exclusively for beverage cans. Each 21-inch-thick metal bar is first heated and rolled into 3,000-foot-long coils an eighth of an inch thick, then cold-milled with massive rollers
that bring the aluminum down to a thickness of a few thousandths of an inch. The Tennessee plant churns out enough of this thin aluminum sheet every minute to make 150,000 cans.
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The 7-foot-wide, 25,000-pound rolls of aluminum next travel by rail to an industrial park in Fairfield, California, to the Ball Metal Beverage Container Corporation plant. Headquartered in Colorado, Ball is one of those immense companies little known to consumers whose products are in so many homes; a $9 billion business with manufacturing plants worldwide, twenty-eight of them in the U.S. That makes Ball the largest beverage can maker in the world, churning out 50 billion cans a year for big soda and beer brands, as well as ghost-brand cans like those that contain refreshe.

The five-mile sheets of aluminum are uncoiled and fed into a cupping press, where rapid-fire blades strike home in a rhythmic, thudding rumble that fills the plant with a sound like a thousand marchers. The press cuts the metal sheets like a batch of silvery cookies, spewing out disks of aluminum several times wider than a finished can. These disks are then “drawn” through a die, meaning they are pushed through a metal doughnut by a cylindrical punch that forms each disk into a shallow cup about 3.5 inches in diameter. At this stage my can looks like a metal petri dish.

A conveyor belt moves this new army of cups to the next machine, the body maker. Each cup is pushed through a smaller die that squeezes it into the proper width of a twelve-ounce soda can, about 2.5 inches. The die forces the flexible aluminum to grow even thinner, the metal redistributed upward from thickness to tallness. At this stage, the can is not yet half its finished height, but it's getting there. This stage is called “redrawing.”

The next stage pushes each cup through a series of increasingly narrow dies that stretch the cup gradually to its proper height while making the walls thinner—like stretching a rubber band, except the metal doesn't snap back. This is called “ironing.”

At the end of the ironing, a dome-shaped die is pressed into the bottom of each can. Whether used in buildings or cans, an arch or dome is stronger and can withstand more pressure than a flat surface. Doming allows the can bottom to be thinner, saving material, weight, and money. Each of the dozens of doming tools on the assembly lines has a unique two-digit number, and those numbers are embossed on the can bottom when the dome shape is pressed into place.

All this happens fast: the redrawing, ironing, and doming of a can takes about one-seventh of a second.

Next the can's open top end is trimmed for a clean edge and uniform height, followed by multiple high-temperature washes, drying, and the painting of labels. The can is baked to harden this “decoration,” as the labels are called, followed by a spray of waterproof varnish inside the can to keep beverages from tasting of aluminum and to protect the can from reacting with acids in a beverage.

The narrow neck of the can is then formed by passing it through a series of eleven “necking sleeves,” then the top is folded over into a flange; the can top can be attached later. The neck (early aluminum cans had little or no necking) is not for aesthetics: it reduces the amount of aluminum needed for each can slightly, reducing its weight as well as cost. While inconsequential for one can, the effect across 100 billion cans is massive: the current amount of necking saves about 100,000 tons of aluminum a year. That's enough to make a solid cube of aluminum 105 feet tall—higher than a ten-story building.

Computerized video cameras scan each can for leaks and imperfections, then the finished cans, their mouths gaping open, are packed on pallets and wrapped in plastic film to hold them in place for shipment to the beverage plant.

A separate machine stamps out the can lids with integrated
pop-tops at a rate of 6,000 a minute. The pull key that opens the can looks like it's riveted in place, but there is no separate rivet; that would break the seal of the can and allow leaks. Instead, the shape of a rivet is drawn out of the aluminum lid material itself, providing a seamless flange that holds the separately made pull key in place with a fold of metal.

The cans and lids are then shipped to the Safeway supermarket chain's bottling plant thirty-two miles away in the San Francisco Bay Area city of Richmond, California. On the refreshe line, ordinary water is mixed with natural lime concentrate and injected with carbon dioxide to give the seltzer its fizz. As soon as the cans are filled, the bottling machinery attaches the lids by folding the metal twice into a double airtight seam without welding or solder—just a little liquid gel inside the folds that hardens into a gasket to prevent even microscopic leaks.

The carbonation inside the can causes twice normal atmospheric pressures. This is why aluminum cans can be so thin: the pressure inside is always pushing out against the walls of the can, making the structure stronger and very difficult to squeeze or damage. This is why crushing a sealed can of soda in your hand is impossible, and why crushing an open can is child's play. This is also why even non-carbonated teas, coffees, juices, and other canned beverages hiss when opened. They are pressurized as well as the top is slammed into place, although inert nitrogen, not carbon dioxide, is used for these drinks. Nitrogen does not make drinks fizzy.

My seltzer left the bottling plant in a twelve-pack carton, entered the Safeway distribution system, and found its way by semitruck to my local market, a subsidiary of the Safeway company called Pavilions. The pack would go on sale for the ridiculously low price of $2.49, the true magic of the ghost brand being its low cost. The next time I would purchase some, the can would
show me a different road map, having been fabricated by Ball's arch can-making rival in the fiercely competitive aluminum business, Rexam,
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at a plant in in the Los Angeles area, then bottled at Safeway's Norwalk plant, a town just ten minutes from my home.

W
hen enough cans have accumulated in my garage—okay, when too many cans have accumulated in my garage so we can't procrastinate anymore—we bring them to the recycling outpost in back of that same supermarket where I purchased them. Because of California's robust container deposit law, we receive a dime refund for every can we turn in, one reason why the state is the national recycling leader. Only ten states impose container deposits on beverages, however, and this explains why, nationwide, America's recycling rate compares unfavorably with Europe's and Japan's. It's also why, despite the value of scrap aluminum, 43 percent of aluminum cans used by consumers still end up thrown away instead of recycled.
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