I’ve never embraced the consume-more-to-consume-less strategy; avoiding waste of any kind seems essential to environmental responsibility. It’s one of the reasons I still drive a conventional gasoline car, and judging by the number of ancient Volvos and VWs I see on the road, I’m not the only one.
But recently I’ve started to wonder if holding on to the old is really beneficial or just a knee-jerk reaction to over-consumption. In this new series of columns, I’ll explore the true environmental costs of objects throughout their lifecycles, from materials collection and product assembly, to the impact of use and beyond to disposal. Together we’ll see if newer is better as we pit products against one another to determine if one has a clear environmental edge.
There are plenty of places in my life where this quandary pops up, but only one of them racks up 10,000 miles each year. When it comes to your carbon footprint, is it better to keep driving the car you already have or buy a new hybrid?
Sure, it would be great if people drove less and bicycled or walked more, but our personal ecosystems are often just too big and time too short to give up the convenience of cars. While gasoline-electric hybrids are no longer the cutting-edge of eco-conscious automotive technology, they’re the most mainstream option. How would the Prius, that iconic hybrid, stack up against my own not-very-new four-door hatchback?
In a 2003 report, UC Davis Institute of Transportation Studies research scientist Mark Delucchi estimated that assembling a car—including turning its component materials into auto parts—produces about 1.8 pounds of carbon dioxide per pound of vehicle. According to Toyota, it takes about the same amount to produce a hybrid, which means that before it’s ever hit the road the Prius has already emitted about 5,220 pounds of greenhouse gas.
What about emissions from refining the gasoline itself? If you add the 19.4 pounds of carbon dioxide produced by burning a gallon of gas to the additional 5.1 pounds of “upstream” emissions Delucchi estimates are needed to make fuel, you’ve produced almost 25 pounds of carbon. That’s like dropping a giant Thanksgiving turkey onto the road every time you burn another gallon.
Armed with these numbers, I began my comparison. I drive about 10,000 miles per year. Since I don’t commute to work, that’s on the low side; the US Environmental Protection Agency puts the national average at about 12,500 miles per year, while Web site FuelEconomy.gov suggests 15,000 miles as an average. You can check how many miles per gallon (mpg) your car gets at FuelEconomy.gov; mine gets a disappointing 22. The 2008 Prius, on the other hand, gets 46. Each year, my car produces 5.56 tons of carbon dioxide to a Prius’ 2.66 tons. That’s a lot of turkeys. At this point as I did the calculation, a small voice in my head started contemplating a craigslist used-car ad.
But that isn’t the whole picture. Since I am considering replacing my existing car with one that must be newly produced, I need to know how long it would take to make up for the emissions involved in manufacturing the Prius—the equivalent of about eighteen tanks of gas. Since I drive 10,000 miles each year, it would take about eleven months for the emissions to balance out. (A person driving 15,000 miles per year in a typical passenger vehicle would reach that point in about six months.) And since I’d be using less gas, I’d be saving over $900 a year at the pump. The clear message: When it comes to emissions, mileage matters more than manufacturing.
How much would driving a Prius reduce my overall carbon footprint? Pinning down a national average is tough, but the EPA’s online carbon calculator sizes the typical footprint at around 10 tons per person each year, and driving makes up about six of those tons. The rest of the emissions come from heating, cooling, electricity, and waste. (The EPA doesn’t factor in air travel, though, and since a round trip cross-country flight emits a ton of carbon dioxide per passenger, that’s a serious omission.) Based on this estimate, a high-mileage vehicle such as a Prius would offer a thirty-four percent carbon footprint reduction after the initial manufacturing emissions recovery period. In my case, there would be a 5,809 pound difference each year, which, even including the manufacturing emissions, translates to an impressive 11.8 fewer tons of carbon dioxide over five years. That’s like erasing my carbon footprint for an entire year.
But we can’t decide yet, since carbon dioxide emissions aren’t the only factor. Tim Lipman at UC Berkeley’s Transportation Sustainability Research Center says that hybrids produce slightly more air pollution during the manufacturing process because of the smelting needed to make the sealed nickel-metal hydride batteries. However, he says that overall, hybrids pollute less since they require less gas and tend to be clean emitters.
There’s also the question of what happens to your old car. If you sell it, it will continue emitting the same amount of carbon dioxide while someone else drives it, so it’s hard to say whether that’s making things better or worse. Maybe your car gets better mileage than the one it’s replacing, or perhaps you’ve kept the new owner from buying a car that gets even worse mileage. On the other hand, perhaps it would be better to send your car to the scrap heap in the sky. These days, most cars don’t rust in the junkyard: more than 85 percent of each car is recycled, and as the recycling process improves, that figure is inching towards 100 percent.
Finally, there’s the financial issue: hybrids are priced at a premium. A new car is an investment no matter what, and with so many hybrids on the road today, there should be an influx of used models soon.
After crunching my way through the whole equation, it seems that in my case the impulse to conserve by making the most of what I’ve got doesn’t take into account vast differences in fuel efficiency. In California, where people drive more than 825 million miles each day, getting the most out of every gallon of gasoline has a tremendous environmental impact. That’s reason enough for me to take another look at consuming a little more in order to use a lot less.
Want to try this yourself? Here’s how to compare your car with a high-mileage vehicle:
1. Choose a hybrid or other high-mileage car for your comparison. Look up the weight of the car in pounds and multiply by 1.8 to estimate the pounds of carbon dioxide emitted during manufacturing.
2. Use FuelEconomy.gov to compare your existing vehicle against the hybrid. You can adjust the tool to reflect your annual mileage and highway-to-city ratio. Note the mpg of both vehicles. This website will give you an emissions estimate, but it doesn’t include the upstream emissions from producing the gas in the first place. We’ll do that in the next step.
3. Divide your annual mileage by the mpg. Multiply that number by 24.5 to determine the annual carbon dioxide emissions of each vehicle. Add the manufacturing emissions to the first year of the hybrid vehicle.
4. Calculate the emissions out over multiple years to assess the difference and determine the carbon footprint reduction.
Though I won’t be able to buy a hybrid tomorrow, this comparison has dramatically altered the way I think about driving. Great—not just good—mileage is far more important than I realized. Upgrading to a more fuel-efficient car has moved to the top of my personal to-do list, and with so many more high-mpg conventional cars and hybrids on the horizon, plus the promise of electric and plug-in hybrid vehicles, this is an exciting time to be considering a new car.
What’s more, thinking about those 25 pounds of carbon dioxide emitted for every gallon of gas I burn inspires me to leave the car at home—to bike, walk, and take public transportation more often, shrinking my footprint as I boost my footsteps.
