Chemistry professor David Tyler has taken an interest in the environmentally sensitive decisions that confront consumers every day: Plastic grocery bags . . . or paper? Take the car to work . . . or public transit? Disposable cups . . . or a ceramic mug that can be used over and over again?

Tyler has surveyed some of the research on these alternatives and has concluded that the environmental impact of some of our “green” choices can be surprising when you consider their effects from cradle to grave-that is, the total impact from the point a product is created from raw materials, through its manufacturing, distribution and consumer use, ending with its disposal or recycling.

These “life-cycle assessments” broaden the conventional definition of environmental impact by taking into account all energy and material inputs and then the related consequences, which could include downsides such as climate change, smog, water pollution, land use, depletion of fossil fuels and more.

There are life-cycle assessments for everything from owning a dog to buying locally grown tomatoes. Tyler’s conclusion? Consider all the options and make an informed decision-some of the things thought to be hard on the environment might not be so bad after all, depending on what’s most important to you.

Q: In looking at the research that’s out there, what have you found regarding plastic shopping bags versus paper or cotton bags?

A: There are really good things about plastic bags-they produce less greenhouse gas, they use less water and they use far fewer chemicals compared to paper or cotton. The carbon footprint- that is, the amount of greenhouse gas that is produced during the life cycle of a plastic bag-is less than that of a paper bag or a cotton tote bag. If the most important environmental impact you wanted to alleviate was global warming, then you would go with plastic.

Q: Why is the carbon footprint for a plastic bag less than that of a paper bag or cotton?
A: Cotton is typically grown on semiarid land so it consumes a huge amount of water and you also need a lot of pesticides. About 25 percent of the pesticides used in this country are used on cotton. Paper is just typically considered a fairly polluting industry. Whereas the petroleum industry, where we get our plastics, doesn’t waste anything. Chemists have had sixty to seventy years to make the production of plastics fairly efficient and so typically there is not a lot of waste in the petroleum industry.

Q: When you point this out at your public talks, what kind of reaction do you get?

A: A lot of people say they don’t believe it. It just feels good to think that cotton is better for the environment than plastic.

Q: How about disposable cups versus ceramic mugs? The thinking is a ceramic mug is better for the environment because it’s reusable.

A: But when you manufacture the mug it has to be fired in a kiln at a very high temperature. That takes a lot of energy. If the manufacturing takes a lot of energy to make something, you have to recover that energy through repeated reuse, but typically with a mug, studies show that you don’t use them enough to break even on the original energy input. You might as well take that petroleum or natural gas that you are using to warm the kiln and make one-use disposable cups.

Q: There is a fun one that you came across regarding owning a dog versus owning an SUV.

A: One life-cycle assessment showed that the average environmental impact of a dog was greater than the environmental impact of a typical SUV-although it should be noted that this was a pretty controversial study. It suggested that the resources needed to produce food over a dog’s life span-especially meat-outweigh those used to make and drive an SUV. What we have discovered is things that involve agriculture often have a high negative environmental impact-and you have to grow food for a dog. The finding wasn’t exclusive to dogs; it applies to other pets, too.

But here’s another way to look at it – pets, to a lot of people, are essential. They provide companionship. Life-cycle assessments cannot take that into account the goodwill that comes from owning a pet.

Q: Clearly, though, an SUV could also be your companion.

A: Absolutely (laughing).

Q: You’ve raised a point that is important for all of these decisions-it depends on what’s most important to you. What are some different values that people might be weighing?

A: There are thirteen or fourteen standard environmental impacts that life-cycle assessments consider. Those impacts include global warming, carbon footprint, human toxicity, algae growth in lakes and other bodies of water, resource consumption, ozone depletion and smog production.

But how those impacts are weighed depends on context. So, for example, if we lived in Los Angeles, anything that created smog would be really high on our list. But in Eugene that’s not so much of an issue. In Eugene, it’s a little easier to say, let’s worry about global warming rather than smog. If you live in a community that doesn’t have much landfill space or you were worried about plastic bags washing into the ocean, then you would want to find alternatives to plastic because it has a longer life span than other materials.

Q: You have an interesting observation about Styrofoam.

A: Styrofoam is a plastic. And the life-cycle assessments show that plastic cups are no worse on the environment than a paper cup.

Q: But people say, “Oh, Styrofoam, it’s going to be in the earth for the rest of our days.”

A: Once again, the carbon footprint is smaller for Styrofoam than for paper cups. There is less energy needed to produce it. People have been told their whole lives about the evils of Styrofoam-and then somebody comes along and says, well, the environmental impacts in a lot of categories for Styrofoam are much better than the alternatives. On the other hand, it takes Styrofoam longer to degrade so this reinforces the point that our consumer choices hinge largely on what’s most important to us. If your main concern is pollution or garbage reduction, you might not choose the Styrofoam cup even though its carbon footprint is lower.

Q: Let’s talk about plastic forks and bioplastic forks. I would guess that a bioplastic fork, which breaks down, is the way to go for environmental stewardship.

A: Bioplastic is considered really good because it degrades-it’s compostable. What they don’t tell you is, it’s compostable in an industrial composter, which means it’s got to be 130 degrees, and it’s got to be turned daily. But very few communities have industrial composting capabilities. You can’t take that bioplastic fork and put it in your backyard grass pile and have it compost. It won’t do that.

Also, because you have to grow the starch that bioplastics are made out of, the carbon footprint is worse than for a polystyrene fork. The other problem is that currently bioplastics are made from starch that comes from corn or potatoes and sometimes even rice, and a lot of people have a real problem with using food for plastics. A huge amount of the U.S. corn crop is diverted to fuel and is now starting to be diverted to bioplastics.

Q: What have you learned about the Bay Area Rapid Transit System versus cars?

A: I always point out that there are many reasons for urging people to take public transportation-relieving congestion is a big one. But if you try to justify that choice based on sustainability, that’s not necessarily a valid conclusion. Researchers did a life-cycle assessment of the BART system in San Francisco versus packing people into cars and having them commute. It takes a lot of energy to make a light rail system and a lot of energy goes into the use of the BART system, and these researchers found that it was basically pretty even in terms of energy use. So there are all kinds of compelling reasons to use public transportation, but from a sustainability point it’s probably a wash.

Q: Help me understand the difference between buying a tomato at the Saturday Market and buying one that came on a truck from California.

A: Here again, there are all kinds of compelling reasons to eat local food. But the conclusion from life-cycle assessment studies is that sustainability is not necessarily one of those reasons. They’ll ship five tons of tomatoes in a truck from California and the cost per mile per tomato is small in terms of fuel used compared to some guy who gets into his old beater truck and drives into the farmers’ market with five pounds of tomatoes he wants to sell that day.

Q: When I go out to Office Max should I buy a pack of brand-new paper or recycled paper?

A: You would assume that recycled paper is the way to go for the environment. And in the United States that seems to be true. But a life-cycle assessment study in England suggested historically it was probably better to incinerate paper and use that energy than it was to recycle the paper. It’s the inefficiency of the recycling plant and the associated recycling process that wasted more energy-in England, apparently it was very energy inefficient. In this country it’s probably okay.

That was a classic study that shows we are making some assumptions about recycling that maybe we shouldn’t be making.

Q: LED lights are touted as the future of lighting. Is that unquestionably a slam dunk that it is good for the environment and good for us?

A: Well, no. The issue with LEDs is that when they do burn out we have to recycle them appropriately. Several studies suggest they contain toxic metals, so we will have to gear up to recycle those systems properly. You save energy as you transition from incandescent bulbs to compact fluorescent light bulbs to LEDs. But at the same time you may be increasing the human toxicity impact-mercury in the case of CFLs and heavy metals in the case of the LEDs.

Q: One more. Let’s say a mother-to-be is choosing between cloth and plastic diapers.

A: They used to refer to this as “the diaper wars.” It depends on the efficiency of the manufacturing plant. If you have a nice modern diaper manufacturing plant that’s making plastic diapers, then go for it. If it is an old inefficient plant, then probably cloth diapers are better. But the cloth is made out of cotton, and then it comes back to all the problems with cotton- where is it grown, how much pesticide is used; the water use is tremendous. And remember, with the cloth diaper you have to wash it-so you’re using water, you’re using energy to heat the water to wash the cloth diaper and so on. It just occurred to me-it’s a “wash.”

And actually the environmental impact of your new baby is so huge compared to the environmental impact of using a cloth or a cotton diaper you’re worrying about the wrong thing. You probably should have considered having one less kid (laughing). That’s a joke, of course.

Q: What recommendations would you make to someone if they really want to make consumer decisions that work for them?

A: Be informed. Life-cycle assessment data can be retrieved on the web. It’s just like when you buy a car; you go online or to the library and you read about it. You also have to decide who you think is a credible source. Depending on the source, you’ll say, “I don’t really believe this person” or “I do believe him or her, the research seems solid.” Doing the research is really the best way to make an informed choice.

Tyler’s Top Ten Environmental Surprises

Life-cycle assessments of our popular “green” consumer choices suggest we may be wise to consider alternatives as well. In some of these assessments, researchers have concluded:

• Plastic bags produce FEWER greenhouse gases than paper or cotton bags.

• Ceramic mugs consume MORE ENERGY than disposable cups.

• The environmental impact of owning a dog CAN BE GREATER than owning an SUV.

• Styrofoam cups produce FEWER greenhouse gases than paper cups.

• Bioplastic forks CAN BE HARDER on the environment than plastic ones.

• The BART system in the San Francisco area USES ABOUT AS MUCH ENERGY as commuters in cars.

• Delivering a large truckload of tomatoes from California to Eugene can be EASIER ON THE ENVIRONMENT than delivering an equivalent amount in small truckloads from local farms.

• Recycled paper CAN CONSUME MORE ENERGY than new paper (at least in England).

• LED lights save energy but increase TOXICITY concerns.

• Plastic diapers can be A GREENER CHOICE than cloth diapers.

This story originally appeared in the Fall 2012 version of CASCADE, a print and online magazine produced by the University of Oregon College of Arts and Sciences.