It’s amazing to me that the big picture often gets overlooked. I am not talking about willful distortion, but about well-intentioned people looking at only one part of the equation in an attempt to arrive at a good but simple solution. Here are two examples, both concerned with reducing pollution.
All over the world, incandescent light bulbs are being phased out in favor of compact fluorescent lamps, which use less energy to emit the same amount of light. Incandescent bulb filaments create light by glowing white-hot, so a lot of electricity is converted into the wasteful byproduct of heat.
Compact fluorescent light bulbs have their own disadvantages: They contain mercury and are toxic, creating a disposal problem. (Don’t throw them in the trash!) They emit a colder, bluish light, which can contribute to the “winter blues” (now called “seasonal affective disorder”). However, the consensus is that to save the Earth, these negatives are worth it.
One question few people have asked is: “Where does the “wasted” energy of an incandescent bulb go?” The answer is simple. It heats the room.
I live in Seattle, where we turn on the lights mostly in winter, when it is cold. When it is cold, we also run the heater. Switching to compact fluorescent light bulbs will decrease my electricity consumption, but it will increase the gas used by my heating system. The net result will be zero energy savings.
For northern regions, the phase-out of incandescent bulbs looked only at one part of the equation, but not the big picture. Of course, if I still lived in Texas, and if I lived in an air-conditioned house rather than one with ceiling fans and cross-ventilation, then the switch to compact fluorescent bulbs would save energy twice: Once with the reduced consumption of the light bulb, and again with the reduced energy use of the air conditioning system. Also, the “winter blues” aren’t so much of a problem in Texas. So it would make sense to phase out incandescent light bulbs in Texas, but keep them in Seattle.
Cars are another issue that requires a nuanced view. Many people recommend replacing older cars with newer ones that get better gas mileage to reduce emissions. Such generalizations overlook the emissions and environmental impact of making the new car. Producing raw materials and manufacturing at car factories cause a lot of pollution. Car parts and finished cars are shipped all over the world, which uses a lot of energy. Generally, it is recognized that 10-15% of a car’s pollution is caused by its manufacture, the rest by driving it. (There also is the environmental impact of disposing of the old car.)
My family’s car is 19 years old, and gets about 25 mpg. That isn’t great: I could buy a Honda Fit that gets 33 mpg – a huge improvement of almost 30%. Wouldn’t that be great for the environment?
The surprising answer is “No.” Our car is driven about 4000 miles a year. That means that the Honda Fit would reduce our family’s annual gasoline consumption from 160 gallons to 121 gallons, a savings of 39 gallons. If the pollution of making the car is equivalent to about 600 gallons of gas (200,000 miles lifespan : 33 mpg x 10%), then the Honda Fit would take over 15 years to “amortize” the pollution caused by its manufacture – if it lasts that long.
Of course, if you drive 40,000 miles a year, then your Honda Fit would amortize its manufacture in less than 2 years, and both the environment and – somewhat later – your budget would come out ahead.
These examples show that simple “one size fits all” solutions tend to overlook crucial nuances. Compact fluorescent light bulbs make a lot of sense in hot climates, but not in Seattle. Replacing an old car with a new, more fuel efficient one makes sense for people who drive a lot, but not for many cyclists who use their bikes as their main transportation.
Similar questions occur in cycling. For example, are wider tires faster? Once again, the answer is: “It depends.” On a smooth indoor track at very high speeds (above), relatively narrow tires at high pressures may be most efficient.
For a long-distance ride at lower speeds (where aerodynamic drag is less important), on rougher roads (where suspension losses can be very large), much wider tires at much lower pressures undoubtedly roll faster.
Simple answers tend to overlook crucial factors. You really have to look at the big picture to make good decisions for your situation.