Hey Mr. Green,
Is it better to drive my minivan to a playground or to buy a swing set?
–Purvika in Mountain Lakes, New Jersey
This is hardly the most urgent environmental question of our times, but such questions are fun to answer, and give Mr. Green a pretext for pontificating about larger issues.
Obviously, there is a mind-boggling set of variables involved here: how far you have to drive to the park, what mileage the minivan gets, the size and material of the swing set, the distance it is shipped, and every other conceivable impact. Pursuing this down to the last kilowatt and drop of water and microparticle of grime can lead to madness. As one agricultural wit asked, "When we assess the environmental impact of growing soybeans, do we have to include the soap and water used in the farmer's shower?"
But since energy use seems to be your main concern, let's focus on comparing how much is needed to make the swing as compared to the energy required to drive your darling(s) to the park. Assuming that you'll survive the current economic collapse and have a yard in which to plant a swing, you could spring for a steel three-seater that weighs 190 pounds or so. According to the U.S. Energy Information Agency, it takes 16,366,000 British thermal units (Btus) to make a ton of steel. So making almost all of the swing would require 1,554,770 Btus. The typical minivan gets 17 miles per gallon in the city, according to the EPA. Gasoline can contain up to 125,000 Btus per gallon. Therefore, the minimum energy needed to drive the minivan about 220 miles would equal the energy it took to make the swing. If you live only a mile from the park, in just 110 visits—twice a week for a year—you'd burn as much energy as it took to make the steel in the swing set. Of course, if you drive farther and settle for a lighter, smaller swing, the energy disadvantage of the minivan increases proportionately.
But if you're only a mile away from the park, why drive there anyhow? Make ‘em walk or bike. It builds character and helps shed the kid blubber that's getting so much attention nowadays. "But it takes too much time to walk or bike!" I already hear the howls of protest. Well, does it really, when you consider how much time it takes to strap in a kid or two, wend your way through gridlock, find parking, unload, reload, and unload again, not to mention the hours you'll have to work to pay the 54-cent-a-mile cost of owning and operating the average vehicle? Hidden behind the automobile's smiling grill of comfort and convenience are some troubling hassles and expenses.