Bottled water for a few people uses more energy than tap water for everyone else


11 Aug 2010

We can’t get drinkable water out of the tap where I live—in Karachi, Pakistan—despite it being a luxury apartment. In fact, we’re not even on the city’s water system.

All our water gets brought in by tanker trucks that arrive a few times a day and fill up an enormous concrete tank on our building’s roof. Even that water’s often undrinkable because it’s a bit salty. It’s perfectly fine for washing dishes and taking showers, though.

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For drinking water, we get refillable jugs from a shop down the street, which only cost Rs 20 (about 25 cents) for a 12 liters (the cube-shaped jug in the middle, above) Compare that with Nestle’s purified bottled water in a 1.5 liter bottle (the small bottle on the right), which is Rs 50 (about 55 cents). Liter for liter, that’s 20 times more expensive than our jugs!

But, to some degree, you get what you pay for. Despite our jugs claiming to be clean, purified water, they’re probably filled by the city’s “water mafia” at illegal, unmetered taps on the city’s water supply, at some point where it is reasonably clean. The jugs don’t seem to get cleaned very often, if ever. So we don’t trust this bottled water enough to drink it straight.

After all, one time, one of the bottles had a thick coating of bright green algae coating the inside, and we noticed only after we’d drank the water. Another time there were mosquito larvae wriggling inside—and that time, we did notice before we drank it. Because of these not-so-pleasant surprises that can come, we pour our cheap bottled water into the big blue 20 liter bottle (on the left, above), and disinfect it with chlorine tablets.

This is all a long way of saying that we can’t take our water for granted. And since I report a lot on energy issues, I was interested to read a recent study, “Energy implications of bottled water”, which breaks down the energy use in each of the processes—purification, bottling, labeling, transport—that bring bottled water from the source to you. In the world of oil, they call this kind of analysis “well-to-wheels”—the energy it takes to get oil out of the ground and into your gas tank. For water, we could call it “well-to-whet.”

I was surprised how the numbers came out. The two big energy hogs are manufacturing the bottle, and transporting it to you. The actual water treatment itself is almost nothing. Keeping the water in the fridge for a few days before you drink it adds a bit of energy, but not much, to the total.

Basically, if you’re drinking locally bottled water, the bottle is the main energy use. If you’re drinking water from far away (Perrier, anyone?) then the energy use is probably about half for the bottle and half transport, depending on how the water made its journey to you.

So if avoid using and tossing plastic bottles, you cut your drinking water footprint enormously. You could, say, buy refillable plastic jugs like the ones we use in Karachi—although without the algae and mosquito larvae, I hope.

Or you could just use tap water. It uses far, far less energy to produce. The new study estimates that bottled water requires around 5-10 million joules for each liter of water. But tap water requires about 5,000 joules per liter—so liter for liter, bottled water uses 1,000 times more energy.

Of course, it does take a lot of energy to build a whole water supply network, and to maintain it. But the numbers for bottled water don’t factor in extra energy use either—like the energy to build water purification and bottling plants, or the trucks, ships, and trains that transport water around. If you tried to factor in all these things for both bottled water and tap water, my guess is that tap would still deliver water with far more energy efficiency.

How much? I decided to do a back-of-the-envelope calculation for how much energy it might take to supply Karachi’s elites with bottled water, and compare that with how much it would take to run a tap water system for the whole city.

There are some 20 million people in the city, and let’s say the elites are 1% of that. (The top 1% seems like a good definition of “elite.”) If the elites drink 3 liters of bottled water a day—for each person, that’s two of those big bottles you can hold in your hand—and the water is locally produced (rather than shipped in from France), then all their bottled water would use something like 3 trillion joules each day.

Let’s say the rest of the elites’ water—for bathing, washing clothes, and so on—comes from the tap. People in developed countries use about 20 liters of water a day, I remember hearing. So lets say Karachi’s elites get 17 more liters of water from the tap. That would use about 170 million joules a day—a tiny fraction of the energy use of the elites’ bottled water. All together, the elites’ water supply would consume 3.00017 trillion joules of energy a day.

If all the rest of the people—the remaining 19,800,000 people—get their water from the tap, that would use about 2 trillion joules each day. That’s less than just the elites’ bottled water!

These are just rough calculations, but it gives an idea of the scale. The elites aren’t all that bad—many buy re-usable jugs of water, which they put on coolers that chill only a small amount of water at a time. That would cut down the energy use in bottling (a big benefit) and cooling (a smaller benefit). In any case, I was astonished at how the numbers came out. I had no idea that bottled water would use so much energy compared with tap water.

This matters for Pakistan, because it’s in the midst of an on-going energy crisis. There’s never enough electricity to go around, so it means that power gets shut off to homes for a few hours a day (at best), which is annoying but not a huge deal. Worse, it gets shut off for factories, making it hard for them to run their businesses, and they have to lay off workers. Here, there’s a coming “youth bulge”, with a huge number of young people who will be entering the work force soon. The country desperately needs to be creating more and more jobs—and to keep doing so for the next generation, at least. Losing jobs because of energy shortfalls is hitting the country hard.

Drinking water isn’t to blame for all of this, of course. But it shows how the energy consumption of the elite can dwarf that of everyone else, even for an item that seems as basic and non-luxurious as clean drinking water.

UPDATE: Bottled water isn’t the only thing we drink out of bottles, of course. Coke and Pepsi are everywhere—even in remote villages in Pakistan. Making soda and getting it to people probably uses about the same amount of energy as for bottled water. (The energy in making the sugar, caffeine, and flavorings for soda probably are a small amount of the energy compared with manufacturing the bottle and transporting the soda around, just as water purification is only a small slice of the energy use in making bottled water.)

So even if everyone gave up bottled water, but if people kept downing soda as just 1% of their drinks, that would probably use more energy than it takes to supply all of their tap water for drinking, cooking, bathing, washing dishes, and so on.

bookshelf

books I've read on failure & grace

The World Without Us
The Last Oil Shock: A Survival Guide to the Imminent Extinction of Petroleum Man
Zeitoun
A Paradise Built in Hell: The Extraordinary Communities That Arise in Disaster
Hell and High Water: Global Warming--the Solution and the Politics--and What We Should Do
The Worst Hard Time: The Untold Story of Those Who Survived the Great American Dust Bowl
The Tipping Point
Three Cups of Tea: One Man's Mission to Promote Peace... One School at a Time
The Upside of Down: Catastrophe, Creativity and the Renewal of Civilization
Out of Poverty: What Works When Traditional Approaches Fail
The Little Ice Age: How Climate Made History, 1300-1850
Confessions of an Eco-Sinner: Tracking Down the Sources of My Stuff
Deep Economy: The Wealth of Communities and the Durable Future
The Geography of Bliss: One Grump's Search for the Happiest Places in the World


Mason's favorite books »

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