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Like many Princeton students, I want to lessen my environmental impact. Therefore, I tried to figure out which changes could lessen it the most. How does taking a shorter shower compare to biking to work? How does using a reusable bottle compare to eating vegetarian?

The answers became very complicated very quickly. For starters, there is no scientific unit for “green.” A common measure is carbon dioxide emissions, but that is only a small part of the picture. Carbon dioxide is not the only greenhouse gas, or even the most potent.

Further complicating matters, climate change is not the only rubric for measuring environmentalism. Air pollution, deforestation, disruption to the local ecology and tainted water are also important things to keep in mind when measuring the greenness of an action or a product. Since I had to start somewhere, I took a look at how we waste water.

Most people never see the water they use. Much more water is used to grow food and create products than people expect. According to the United States Geological Survey, it takes about 460 gallons of water to make four ounces of beef, or the amount in a single hamburger. For comparison, a typical shower uses 2.1 gallons per minute. Someone would have to shower for over half an hour per day, every day, for a week to equal the water in a hamburger.

While beef frequently gets trotted out as an example of bad water efficiency, other foods are not much better. A three-egg omelet is 150 gallons just for the eggs. A cup of orange juice is 45 gallons. What you eat and drink uses much more water than any reasonable amount of showering possibly could.

Paper is also a terrible water-waster. Here there is a considerable range, but the USGS says three gallons per sheet is a reasonable average. All the paper towels you use to dry your hands after using the bathroom throughout the day probably took more water to produce than the water you used while showering.

But comparing water use alone is not a fair metric. A shower uses hot water, and that takes energy, which often implies carbon dioxide emissions. While the exact amount varies significantly based on how the electricity is produced — obviously, solar, wind, hydropower and nuclear are better than coal or natural gas — and other factors such as heater efficiency, ultimately half a pound of carbon dioxide per minute of showering is fairly reasonable.

Cars emit roughly one pound of carbon dioxide per mile, which means a five mile drive produces as much carbon dioxide as a ten minute shower. Cars are thought of as carbon dioxide factories, but a shower is not much better.

That result shocked me because I thought my article would be about why taking shorter showers does not make a big difference. I thought I would be writing about how recycling paper, thinking about food choices and riding a bicycle more often have much greater effects.

One could say that carbon dioxide is not all that bad, as long as we are responsible at buy carbon offsets to offset our emissions. Sadly, carbon offsets do not actually remove carbon dioxide from the atmosphere, they are just an investment in renewable energy and other green things. While such investment are good, carbon offsets are treated as the indulgences of the environmental movement, as if purchasing one magically makes the carbon dioxide go away.

The actual data show that it all depends on how you look at it. If environmentalism is looked at through the lens of saving water, then long showers are not a big deal. If you look at carbon dioxide, then showers are pretty bad.

I only examined water and carbon dioxide, not other factors. Methane, for example, is a more potent greenhouse gas than dioxide. Food production uses chemicals that can cause runoff into streams and rivers. Different ways of producing electricity differ by more than how much carbon dioxide they produce. Hydropower changes the river’s ecosystem. Wind turbines can harm bird migrations. Coal involves strip mining, but natural gas fracking creates earthquakes.

The largest problem I encountered while trying to crunch the numbers on greenness is nearly endless recursion. If I really wanted to look at the carbon dioxide emissions of a car, then perhaps I should also factor in the energy required to extract, process and transport the gasoline. But then I should also factor in the increased food I would have to eat to ride a bike instead of driving. The questions are endless.

Whether a shower is worse than a drive may be impossible to judge, but both have an impact. Be mindful of that impact and the complexity of “green.”

Beni Snow is a freshman from Newton, Mass. He can be reached at bsnow@princeton.edu.

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