I wrote this post about a year ago, but it still serves as a great example of how a student question can lead to a powerful learning opportunity:
How many plastic bottles are made each year in the United States?
This seems like a simple question, but it turns out to be pretty complicated.
I got interested in this topic because my son read this fun book in Kindergarten:
The book says that more than 10 million plastic bottles are made every day in the United States. That seemed hard to believe –10 million per day times 365 days per year would make 3.65 billion plastic bottles per year! Where would we put them all?
To break it down, that would be 416,666 bottles per hour, or nearly 7,000 per minute.
That’s about 115 bottles made every second!
That seemed ridiculously big, so I did some research.
It turns out that number is wrong. The actual number is about ten times bigger. That’s right — it’s closer to 1500 bottles per second, according to this source from 2009.
One of the things we will focus on at Triangle Learning Community Middle School is thinking critically about our sources. If you click the source above, it takes you to “treehugger.com” which suggests that the numbers found there might be inflated to exaggerate the point.
If the US does make 1500 bottles per second, that means 90,000 per minute, and 5.4 million per hour. My son’s book said 10 million per day, but if these numbers are right, it’s more than 10 million in just two hours. For a day, the total would be 129,600,000 bottles. And if you multiply that by 365 days per year, the yearly total is more than 47 billion bottles.
That may be a little high — but it seems more in the ballpark than the estimate from the book my son read. Take a look at this search I ran on Google:
There’s quite a range in those results — from 29.8 billion to 50 billion. But that’s just a difference in magnitude of two — my son’s book had the figure at 3.65 billion per year — that’s smaller than the 29.8 billion figure by a magnitude of nearly 10.
Now things get interesting — what is the difference between bottles of water and bottles? What other sorts of plastic bottles are being made? What other plastic products are being made? How is plastic made? And how long does it take for plastic to decompose? Is there a difference between bottles made and bottles consumed? How many plastic bottles does the US import every year?
In my son’s book, the bottle gets recycled and becomes a fleece sweater on an astronaut, which is a happy ending. But what percent of the bottles consumed in the US actually get recycled?
Wikipedia’s article about bottled water says:
The global bottled water sales have increased dramatically over the past several decades, reaching a valuation of around $60 billion and a volume of more than 115,000,000 cubic metres (3.0×1010 US gal) in 2006. U.S. sales reached around 30 billion bottles of water in 2008, a slight drop from 2007 levels
The rate of consumption more than quadrupled between 1990 and 2005. Spring water and purified tap water are currently the leading global sellers. By one estimate, approximately 50 billion bottles of water are consumed per annum in the U.S. and around 200 billion bottles globally.
If we follow the link to source #4 above, we can find a column from the New York Times from 2008, titled A Fountain on Every Corner, that argues we should lay off the bottled water. That column says that “we’re a grab-and-go society, consuming roughly 50 billion bottles of water a year.”
Presumably, the 50 billion is in the US, rather than in the world. I wonder if anyone has global figures for bottled water consumption in 2013…
Here’s a chart from the Worldwatch Institute that compares water consumption from 2000 to 2005 in a selection of countries that consume lots of bottled water:
As I look at this chart, I notice that the US is number one, consuming about 17 percent of the world’s bottled water. But I’m also interested in consumption per person. The US is not number one there…
In 2005 Italy is number one at 191.9 liters per person, with Mexico a close second at 179.7 liters per person. The US is not even in the top 5, with “just” 99 liters per person, but we are up more than 50% from 2000, when we consumed an average of 61 liters per person.
And the US has a population of about 315 million, compared with 112 million for Mexico and 59 million for Italy (according to Wikipedia’s list of countries by population)
That’s a lot of data to think about. But students can handle data — we just have to slow down and think. That’s a key skill for today’s world — handling and making sense of massive amounts of information. And this isn’t even all that massive.
Given this data, we could have quite a thoughtful discussion about bottled water. Once we discussed the topic, we would stop and give each student a chance to write about what he/she found most interesting in the discussion. Assuming students were interested, we could continue the discussion the next day, or even plan a project that explored some combination of plastic production and/or water consumption. Is there a way to find out how much bottled water is consumed in Durham County and/or in the Triangle?
And do we really need bottled water?
A project I am interested in doing would be to have students test the tap water at each of our houses in the Triangle and at a variety of locations around Durham, including nearby Ellerbe Creek. We’d measure for a variety of substances, and we would get a portrait of how clean and safe our water is to drink.
We’d then report about what we learned, perhaps by making a short video that we could post on a local government website to let people know about their water quality. The plastic bottle project could be coupled with this water quality project.
It’s science, combined with math and communication skills. That’s how students should be allowed to approach the world — in a multi-disciplinary and engaging way that results in real work that students can share with the world.