Buy a better earth: Science World goes shopping for the environment.

How much cash did you burn through at the mall last weekend? Each year, young people spend $170 billion on food, clothing, and entertainment. But all that stuff costs more than you think.

"A lot of consumers don't realize the hidden costs behind what they buy," says Lisa Mastny of the Worldwatch Institute. "Anything from a CD or DVD to clothes and cars has a story beyond what it's used for. There's a connection between the product and its impact on the environment."

Take our shopper's quiz, (right), to find out how well you know what your money buys. Then read on to learn how to make purchases that won't add up to an expensive shopping trip for Planet Earth.

EXPENSIVE ELECTRONICS

In 1999, more than 10 percent of America's electricity was used to power gadgets like computers, alarm clocks, and cell-phone chargers (see chart, below). That's enough energy to power Ecuador for at least 10 years! The kicker: Half of all the energy an electronic device uses is sucked up in standby mode, or when it's not in use but still plugged in.

That means there's no need to give up CDs or American Idol. "Using [electronics] less is not going to make as much of a difference as unplugging them," says Karen Herter, an energy researcher at Lawrence Berkeley National Laboratories. The best thing you can do, she says, is buy Environmental Protection Agency-rated "Energy Star" electronics that are more efficient in standby mode.

YO-YO SOLUTION

A stereo gets its energy from a cord plugged into the wall. But what powers all those gadgets in your backpack or purse? Most small electronics like cell phones, PDAs, and portable CD players run on batteries. The hidden cost: Many of those batteries recharge with electricity from an outlet. That's why engineers Chris Aimone and Tomek Bartczak designed the reGen MP3 player. It uses energy from a spinning yo-yo to crank out music.

Here's how it works: Fresh out of your hand, a dropped yo-yo has potential energy (stored energy). As the yo-yo falls, some of that potential energy turns into rotational kinetic energy (energy of spinning motion), which whirls the yo-yo. As the disc nears the bottom of the string, it has converted all its potential energy into kinetic energy. "You can see when it has more kinetic energy because it spins faster," says Gordon Jones, a physicist at Hamilton College in Clinton, New York.

But the toy gets most of its power from your yo-yoing arm. "You can throw the yo-yo down as hard as you throw a ball," says Aimone. The energy from your arm muscles transfers to the yo-yo and makes it spin even faster.

A professional yo-yoer can keep the disc spinning at the bottom of the string for minutes. At this stage, the pros use the kinetic energy of the spinning yo-yo, to do tricks like "walk the dog." But in the reGen yo-yo, that energy is used to charge the MP3 player's batteries. "It's like a yo-yo trick, but you pull that energy out to do something useful," says Jones.

Only 10 to 12 swings of the yo-yo is good for up to an hour of listening. Now that's music to your ears!

GRAPH IT!

Using the chart (left), create a bar graph to compare the five most energy-hungry devices. How can you reduce your energy consumption?

PAPER DOESN'T PAY

Next tinge you pass a note to a friend or clean a spill with paper towels, consider this: You're using part of a tree. The paper for these products comes from wood that's shredded, pulverized, and mixed with thousands of gallons of water and chemicals to create wood pulp (water-and-wood mixture). The process takes precious energy and water, not to mention valuable trees.

Eighty percent of the world's original forests have already been bulldozed. That means fewer habitats for wildlife, less oxygen-producing vegetation, and more erosion (washing away) of soil no longer anchored by tree roots.

It also takes more water to make a ton of paper than it does to make any other industrial product in the U.S. And paper mills are the nation's second-largest energy consumer.

A smart shopper's job? Consider more than just the color of a notebook cover or the paper towel's pattern. Flip the package over and look for a label that says "this product contains post-consumer waste (recycled materials)." Paper made from recycled materials uses less water and energy and doesn't require more trees.

But beware: There's no standard label for eco-friendly paper products. "A label that says 'Earth-friendly' could be [made from] anything," says Mastny. "The clearer the label, the better."

SPENDER BENDER

One day futuristic electronic paper, or e-paper, could cram all of your heavy textbooks into one lightweight notebook. Flexible like a magazine, e-paper stores loads of information in its computer chips and rolls up like a pen-sized scroll to fit snugly in your pocket. "The technology allows people to carry large amounts of information with them in an easy-to-read format," says Darren Bischoff of E-Ink, one company developing the technology.

The e-paper is made of plastic coated with tiny microcapsules, or beads. The beads are filled with a clear liquid that holds thousands of tiny black and white particles. The black particles have a negative electrical charge (when atoms or molecules in a material lose or gain electrons, or particles that orbit an atom's center), and the white particles are positively charged.

Electric fields (a region of electric charge) control the text on the screen by changing the color of the beads. Because opposite charges attract, a positive field, for example, forces the negatively charged black particles to rise to the top of the liquid. The white beads scram to the bottom, and the spot appears black. When hundreds of black beads meet up on a screen, they form letters and words.

Someday, the flexible screens will download information from a wireless link to your cell phone. But this technology is at least five years away. Right now, Philips electronics has a rigid glass-based version of the plastic screen that they will sell in Japan starting next year. If they're successful, paper books and newspapers may become a thing of the past.

"We don't expect to fully replace paper," says Bischoff. "But the technology has the potential to allow people to use less paper."

RESEARCH IT:

How are plastics made? How do these processes affect the environment?

DEBATE IT:

Use your research on plastics and the information on trees in the chart (p. 18) to decide: Is it more, or less, environmentally friendly to use e-paper instead of pulp-based paper?

ENERGY EATERS        ANNUAL ENERGY
                      CONSUMPTION
ELECTRONIC DEVICE      (TWh/year)

TV                        30.8
COMPONENT STEREO          11.4
CELL PHONE                 0.6
ALARM CLOCK                1.9
COMPUTER                  24.9

Source: Lawrence Berkeley National Laboratories

TREE TALLY

In 2001, Americans threw away more than 81 million tons of paper
products. Only 45 percent of that was recycled. Complete the chart
below, to see how many trees were cut down to make each waste
product. Hint: 17 trees = 1 ton of paper.

PRODUCT                       TONS OF PAPER   NUMBER OF TREES

NEWSPAPERS                      12,200,000
TELEPHONE DIRECTORIES              740,000
FACIAL TISSUES & PAPER TOWELS    3,260,000
MILK CARTONS                       510,000
CARDBOARD BOXES                 28,980,000

TOTAL ANNUAL CONSUMPTION             0.331
OF PAPER PER PERSON

Source: U.S. Environmental Protection Agency. 2001

SHOPPER'S QUIZ: What does your money buy?

1. Which of the following CANNOT be used to paper?

a) blue jeans

b) trees

c) human hair

d) blue jeans

2. How many cell phones do Americans throw away each year?

a) 500,000

b) 10 million

c) 90 million

d) 130 million

3. What does the recycle symbol on paper products mean?

a) made from recycled materials

b) cannot be recycled

c) can only be recycled in certain states

d) there is no exact meaning

4. Which of the following corporations has an ongoing program to help introduce environmentally friendly practices?

a) Coca-Cola

b) Nike

c) Wal-Mart

d) all of the above

5. Which of the following is a common environmental hazard associated with the production of a cotton T-shirt?

a) water pollution

b) oil Spills

c) fossil-fuel consumption

d) all of the above

SHOP SMARTER

Every year the average American buys about 48 pieces of clothing and consumes more than 350 canned sodas. If everyone in the world bought and disposed of goods the way do today, it four more Planet Earths to provide all the raw materials to make those products, according to the environmental group Redefining Progress. The world's use of natural resources is not sustainable: "There aren't enough resources on this planet to consume like we do," says Mastny.

The problem will only get worse as the world population soars. More people on Earth means they'll use more resources simply to survive, let alone buy a cell phone or a car. The bad news: Any technological progress we make today, such as more energy-efficient electronics or cell-phone recycling, may not be enough to counteract the future strain on resources, says the Worldwatch Institute.

But that doesn't mean you should ignore the problem. You can help the environment by making smart choices next time you hit the mall. "We're not asking people to deprive themselves of things or not buy at all, but to buy differently," says Mastny. "Get the facts and share them with your friends. Then if you have to buy something, choose the option that's better for the health of the environment."

POPULATION CALCULATIONS

Earth's current population is more than 6 billion people, 75 percent of whom own at least one TV set. Use the graph to calculate how many more people will own at least one TV in 2020 if the same percent of the population owns a TV.

[GRAPHIC OMITTED]

Did You Know?

* Using recycled materials instead of virgin tree fibers to produce paper creates 74 percent less air pollution and 35 percent less water pollution.

* Know how to save 60,000 trees and 25.0 million gallons of water? Have one out of every 10 students in the U.S. buy a notebook made from recycled paper.

* How much trash does the computer age generate in the U.S. per month? More than 45 tons of CDs and DVDs become outdated, useless, or unwanted. Also, 55 million boxes of unused software go to landfills and incinerators.

* It takes an average of 600 gallons of water from start to finish to make one quarter pound burger.

Buy a Better Earth, p. 16 Graph It:

[GRAPHIC OMITTED]

Tree Tally: Number of trees: 207,400,000; 12,580,000; 55,420,000; 8,670,000; 492,660,000; 5.6

Population Calculations: Answers will vary due to graph estimates. This answer was obtained using 6 billion as the original population and 7.5 billion as the population in 2020: 1.125 billion more people will own TVs in 2020

Resources

This Web site was created by the Center for a New American Dream to educate teens about consumerism and the environment. It has fun quizzes, printable fact sheets, and music files to download: www.ibuydifferent.org

World Watch Institute has a series of reports on smart buying. Read them at: www.worldwatch.org/topics/consumption/

The U.S. Environmental Protection Agency has hundreds of resources for buying environmentally friendly products. Check out: www.epa.gov/opptintr/epp/

Check out this Web site to track the progress of the reGen yo-yo and find out when it will reach stores. You can also learn more from the inventors on how this gadget works: www.mp3-yoyo.com/