The Green Lantern

Grande Americano, Extra Green

What’s the best way to drink your morning joe?

My office recently switched from Styrofoam coffee cups to a “bring your own mug” policy. Sounds like the right idea, but with all the water and paper towels we now waste on washing mugs, I’m not sure this is a huge net gain for the environment. What is the “greenest” way to drink coffee around the office?

Judging from all the letters the Lantern gets on this topic, you and your office-mates are not alone in being confused about how to balance a caffeine addiction with a concern about responsible consumption. It’s true: You’ll have a hard time finding a more eco-unfriendly product than the material most of us call Styrofoam. Those soft, white cups are made of highly processed petroleum (polystyrene, to be exact), and they’re almost certain to languish in a landfill for centuries. Still, it may not always be the right move to switch over to ceramic or stainless-steel mugs. It all comes down to which aspects of the environment you care about most.

If your biggest concern is landfill waste, there’s no question that a reusable cup is best. While it’s technically possible to recycle a polystyrene cup or a paper cup, your office will be hard-pressed to find a way to do so: Polystyrene recyclers are difficult to find, and the waxy coating on paper cups—not to mention the leftover food residue—makes it equally unlikely that these cups will find a second life. If you use a disposable cup, it’s going to linger a long while on this Earth—polystyrene isn’t biodegradable at all, and for all practical purposes, you shouldn’t expect a paper cup to degrade very fast in a landfill, either.

But water use matters, too—especially if you’re living in parts of the country, like South Carolina or California, that have recently faced droughts. By this measure, using a mug doesn’t look quite as good, given that each wash will require substantially more water than it takes to make a polystyrene or paper cup.

Finally, there’s the question of energy use and emissions. Here, the results get a little more complicated. Pound-for-pound, petroleum-based polystyrene is a pretty bad material—it takes twice as much energy to produce a gram of polystyrene as it does to produce the same quantity of ceramic. But you’ll need at least 70 times as much energy to produce a ceramic mug as you will to manufacture a polystyrene cup, and probably even more to produce a stainless steel mug.

How could that be? Simply speaking, it’s all about mass: A polystyrene cup is much lighter than a permanent mug. That means it requires far less material, so the fact that it’s made from petroleum is more than made up for by the greater mass of the mugs. It also takes less energy to ship the lighter, disposable cups, and they’re more likely to be produced here in the United States. (Stainless-steel mugs tend to come from overseas, although you should check the labels for yourself.)

Washing your mug will add to its energy burden. Research from the early 1990s suggests that each time you clean a mug in the dishwasher, it takes about as much energy—and would probably produce as many emissions—as it takes simply to produce a new polystyrene cup. Gains in dishwasher efficiency since then may have changed the math a little, but if you wash your mug after every use, you could easily be talking hundreds of cups of coffee before your mug makes more sense than a daily dose of polystyrene. As the Lantern has pointed out before, washing the mug by hand may not absolve you, either—although you can help your case by using cold water.

The Lantern uses a mug for office beverages, but he’s chosen to go the scavenger route—using an old one someone left in his office. Your colleagues’ instincts are right to avoid polystyrene, but they shouldn’t buy brand-new mugs as a replacement (even the kind that come with cheeky green messages). Unless you absolutely need to drink your coffee on the go, ceramic is better than stainless steel. And when you wash, do it by hand, using phosphate-free soap and cold water. (If you want to use hot water, see if you can share washing duties throughout the office, so the water doesn’t need to be heated separately for each mug.)

What if you get your coffee at the local Starbucks on your way to work? The nationwide chain deserves credit for including 10 percent recycled content in its cups, and paper—unlike polystyrene—has the advantage of being a renewable resource. But in other ways, the wood-based venti cups are even worse than office polystyrene: They’re heavier, which means more energy used to create the cup and more waste once the cups have been crushed. Other coffee retailers are experimenting with cups made out of plant-based material, which can then be composted—a positive step, although one that raises a question of where all that extra corn will come from.

Starbucks and other coffee chains are also talking more seriously about encouraging people to use reusable mugs if they are drinking coffee in the store. (Starbucks, for example, says it wants to increase mug use tenfold by 2010.) That’s probably a good step—but the Lantern hopes the company is thinking seriously about its baristas’ dishwashing habits, too.

Is there an environmental quandary that’s been keeping you up at night? Send it to, and check this space every Tuesday.