The Low Carb(on) Diet

By Brianne McCleary

Recently, Peter Miller and his wife PJ went on a diet. A carbon diet. They wanted to see exactly how far they could reduce their CO2 emissions and measure the overall impact of doing so. They also extrapolated the numbers to see what the overall impact would be if everyone in America also tightened their belts.

The full ten page article from National Geographic can be found here, but I'll highlight the main points below.

The Quest
Peter and his wife convinced their neighbors to join in their quest. Each household tracked their total CO2 output. Some key statistics:

- The average U.S. household produces about 150 pounds of CO2 a day by doing commonplace things like turning on air-conditioning or driving cars.
- That's more than twice the European average and almost five times the global average, mostly because Americans drive more and have bigger houses.

After checking with Tim Flannery, author of The Weather Makers: How Man Is Changing the Climate and What It Means for Life on Earth, Peter and P.J. decided to shoot for 80% less CO2 emissions than the American average which equated to reducing use to a total of about 30 pounds of CO2 per day.

Measuring The Impact

PJ was in charge of reading the electric meter and checking the odometer on the Mazda Miata. Peter wrote down the mileage from the Honda CR-V and read the natural gas meter. Everything was diligently tracked on a list on the kitchen cabinet. Immediately, the Millers learned some important stats:

- A gallon of gasoline adds a whopping 19.6 pounds of CO2 to the atmosphere
- A kilowatt-hour (kWh) of electricity in the U.S. produces 1.5 pounds of CO2
- Every 100 cubic feet of natural gas emits 12 pounds of CO2

The Millers used website calculators to get an idea of their current carbon footprint. The Environmental Protection Agency (EPA) website figured our annual CO2 emissions at 54,273 pounds, 30 percent higher than the average American family with two people. They had further to go than they thought.

A Greener Lawn
Peter's first mission was to do some yardwork with less CO2 than usual after he learned the average gasoline-powered push mower puts out as much pollution per hour as eleven cars — and a riding mower as much as 34 cars.

After a failed search for an old-fashioned reel push mower, Peter realized that just the errands that he and P.J. had run that day and common acts such as cooking dinner and drying clothes had them over 100 pounds of CO2 for the day, three times their target.

Vampire Energy
Contemplating how to save energy, Peter had a "vampire energy revelation". He sat up in bed, squinted into the darkness, and counted ten little lights: cell phone charger, desktop calculator, laptop computer, printer, clock radio, cable TV box, camera battery recharger, carbon monoxide detector, cordless phone base, smoke detector. Peter learned from a study by the Lawrence Berkeley National Laboratory that "vampire" power sucked up by electronics in standby mode can add up to 8 percent of a house's electric bill.

After returning from a trip to Oregon to attend his niece's wedding, Peter did some more research and turned up the following stats and facts:

- The United States produces a fifth of the world's CO2 emissions, about six billion metric tons a year.
- That staggering amount could reach seven billion by 2030, as our population and economy continue to grow.

It's the buildings, not the cars

Most of the CO2 comes from energy consumed by buildings, vehicles, and industries. Buildings, not cars, produce the most CO2 in the United States. Private residences, shopping malls, warehouses, and offices account for 38 percent of the nation's emissions, mainly because of electricity use. It doesn't help that the average new house in the United States is 45 percent bigger than it was 30 years ago. Companies that own their buildings, like Wal-Mart can realize significant savings from investing in energy efficiency, but commercial building owners have had little incentive to pay more for improvements like high-efficiency windows, lights, heating, or cooling systems since their tenants, not they, pay the energy bills.

Homeowners aren't helping. Energy efficiency takes a backseat whenever money is tight. In a 2007 survey of Americans, 60 percent said they didn't have enough savings to pay for energy-related renovations. If given an extra $10,000 to work with, only 24 percent said they would invest in efficiency. What did the rest want? Granite countertops.

The biggest CO2 culprit is buildings (38%), closely followed by transportation (34%) and the industrial sector (28%).

What's the impact?

Peter wondered how the numbers added up? How much CO2 could we save if the whole nation went on a low carbon diet? He found a study by McKinsey & Company, a management consulting firm, that estimated that the United States could avoid 1.3 billion tons of CO2 emissions a year, using only existing technologies that would pay for themselves in savings. Instead of growing by more than a billion tons by 2020, annual emissions in the U.S. would drop by 200 million tons a year.

Did it work?
Eventually, Peter and PJ got into the flow of the reduced carbon lifestyle. They walked to the neighborhood pool instead of driving, biked to the farmers market on Saturday morning, Peter worked from home, and when he did commute he took the bus and subway.

Compared with the previous July, they slashed electricity use by 70 percent, natural gas by 40 percent, and reduced their driving to half the national average. In terms of CO2, they trimmed their emissions to an average of 70.5 pounds a day, twice their targeted goal but only half the national average.

Or so they thought.

Their round-trip flight added the equivalent of 2,500 pounds of CO2 to their bottom line, more than doubling their daily average from 70.5 pounds of CO2 to 150 pounds — five times their goal. Air travel caused a huge CO2 impact.

Their neighbors had mixed results. The Bauers got down to 97.4 pounds of CO2 a day but the Freedmans couldn't eliminate driving where they needed to go and ended at 248 pounds daily.

Efficiency, in the end, can only take us so far. To get the deeper reductions we need, as Tim Flannery advised — 80 percent by 2050, we must replace fossil fuels faster with renewable energy from wind farms, solar plants, geothermal facilities, and biofuels. We must slow deforestation, which is an additional source of greenhouse gases. And we must develop technologies to capture and bury carbon dioxide from existing power plants. Efficiency can buy us time — perhaps as much as two decades — to figure out how to remove carbon from the world's diet.