What Makes a Pound of Carbon Dioxide?

The average American generates about 7.8 tons of carbon dioxide per year powering their homes and driving their cars. That is about the weight of two full-grown elephants and works out to about 47 pounds of CO2 a day for every man, woman and child in the country. How do we do it ... and what is a pound of CO2 anyway?

It helps to think of that CO2 as being trapped in a balloon. A one-pound CO2 balloon would be about 2.5 feet wide. Forty-seven such balloons would fill up your living room—every day.

How do Americans generate so much CO2? Nearly a third of the carbon dioxide emissions generated in the U.S. come from transportation, and of those emissions nearly two-thirds come from personal automobiles. When combusted, each gallon of gas creates about 25.3 big balloons—or pounds—of carbon dioxide. Here's how it breaks down. A gallon weighs a little over 6 pounds, 85 percent of which is carbon, giving 5.25 pounds of carbon per gallon. Each carbon atom combines with two oxygen atoms from the atmosphere when it burns, adding 14 pounds per gallon, for a total emission of 5.25 + 14 = 19.25 pounds of CO2. Just to produce gasoline from oil creates an additional 6.05 pounds of carbon dioxide, giving 25.3 balloons of CO2 for every gallon.

Keeping the lights on

Another big chunk of CO2 comes from making the electricity that lights our homes and runs air conditioners, refrigerators and other appliances. Coal-fired power plants, which account for half of all electricity generated in the U.S., release roughly 2 billion tons of CO2 annually while natural gas power plants emit 400 million tons. "The average coal plant emits about twice as much CO2 as a high-efficiency natural gas plant," says Jeffery Greenblatt, Ph.D., a scientist with the Climate and Air Program at Environmental Defense.

The pounds of CO2 emitted per kilowatt-hour (one hour's use of one kilowatt of energy) vary depending on the type of fuel your utility uses. Coal-fired power plants emit up to 2.49 lbs/kWh while wind and other renewable energy sources release none. The national average, combining all energy generation methods, is about 1.34 lbs/kWh. A single 75 watt bulb burning for two hours a day generates an average of six pounds, or six big balloons, of carbon dioxide a month.

So don't balloon up with CO2—this is weight we can all do without.

What you can do

To find out how you can reduce the number of pounds of CO2 that you generate at home, visit www.thegreenguide.com/doc/119/calculator

Replace incandescent light bulbs with compact fluorescent lightbulbs (CFLs).

Turn down your thermostat at night and when no one is home.

Improve the insulation in your home by sealing gaps around chimneys, windows and doors. See more energy saving tips at hes.lbl.gov

Switch to Energy Star appliances, see www.energystar.gov

Purchase green power from non-polluting sources, such as windmills, through your local utility. To find out if green power is available in your area, visit the Department of Energy's green pricing page at www.eere.energy.gov/greenpower/. You can compare the costs and environmental benefits of green power options at www.powerscorecard.org/.

If you're considering offsetting your carbon dioxide, see "Shifting Into Neutral."

Carbon Calculators

The Green Guide's Green Home calculators for household appliances: www.thegreenguide.com/green_home/

EPA's "How clean is the electricity I use?" webpage: www.epa.gov/solar/powerprofiler.htm

Environmental Defense's personal impact calculator: www.fightglobalwarming.com/carboncalculator.cfm