Q: Is it possible to recycle used paper towels? If so, why aren't there recycling containers for them in public restrooms (like at airports or business offices)? If there is some barrier to recycling them, what would it take to overcome it—be it a process to make them recyclable, or a viable system to collect and recycle them?

Asked by Andy Grubb, '05, Oceanside, Calif.

Imagine, for a moment, a life without paper towels. Okay, I guess it isn't that hard to do, but still, the disposable paper cloths are nearly ubiquitous. We use them in public bathrooms to reduce the chance of transferring germs, and at home for all kinds of cleaning activities, but it seems a big waste when we throw them away after just one use. Each sheet of paper towel weighs just two or three grams. If we assume that everyone in the United States uses five sheets of paper towel each day, then we're generating more than 6 million pounds of paper waste a day. That represents landfill space about the size of two large swimming pools in the Water Cube at the 2008 summer Olympic games. And in the oxygen-starved conditions of a landfill, paper towels break down and generate methane, a greenhouse gas that is 23 times more potent than carbon dioxide.

Unfortunately, paper towels cannot be recycled the way other paper products are because the fibers usually are too short to be used again. These days, paper towels are generally made from recycled paper, and the paper fibers get shorter with each reuse. Papermaking fibers can typically be recycled five to seven times before they become too short to be recycled again, and paper towels and napkins are the last stop in the recycling chain. In addition, only clean recovered paper that is free of contaminants (such as food and trash) can be recycled at all, and paper towels exist to clean messes. There are also concerns that germs, food and mold on these disposable products will contaminate clean paper in the recycling bins, which is the same reason we don't recycle (long-fibered) pizza boxes as paper waste.

But if recycling is out, there are still better options than the landfill. The same characteristics that make paper towels poor candidates for recycling make them good for composting, a process that neutralizes germs and turns all those short fibers and messy spills into cheap, high-quality mulch for gardens. Better yet, the controlled composting process ensures that the greenhouse gas generated is mainly carbon dioxide, not the more potent methane.

Large-scale composting facilities are increasingly common in the United States, but it's a safe bet that most paper towels are still heading to the landfill. You could add some unbleached paper towels to your home compost pile, but for heavier loads, a municipal or commercial operation is a better bet. You can find facilities in your area at findacomposter.com. Some waste-disposal companies will accept paper towels as part of your yard waste. There are other options too—like using low-energy air dryers in public restrooms, or using reusable rags or cloths at home. But are those better for the environment? We've got the answer for the air dryers this month, but the rags are another question altogether—why not ask it?

Jingshi Wu is a PhD candidate in the department of geological and environmental sciences.