This is a classic everyday environmental conundrum: What type of bag to choose at the grocery store. The green answer is: neither.

Reduce, reuse, recycle. One way to reduce your consumption of new bags is to reuse the bags you have. Bring your plastic or paper grocery bags back to the store and have the cashier use those. Many stores will give you a 3-to-5 cent credit per bag.

Invest in a sturdy reusable shopping bag made out of canvas, mesh or hemp. Buy a bunch of reusable bags and leave a few in your car so they're there when you go to the store. These bags will last decades and you won't have paper or plastic bags piling up in your home.

If you're stuck at the store without your own bag, then choose plastic.

Why plastic? Making a plastic bag requires fewer natural resources and produces less pollution than making a paper bag. Plastic bags do take five to 1,000 years to decompose, but paper bags take about the same amount of time due to poor landfill design. (See The Live Earth Global Warming Survival Handbook, by David de Rothschild.)

We consume 12 million barrels of oil each year to produce the 100 billion plastic bags Americans use (and mostly discard) per annum. That's 333 bags per person, per year! Do you really need a new bag practically every day?

Also, some three percent of plastic bags worldwide end up as litter. When the bags get into waterways, they kill many birds, fish and other aquatic life every year. So, even though it's better than paper, plastic has its downside.

Above all, remember to keep the issue in perspective. According to columnists from the Sierra Club and Grist magazine, the paper vs. plastic debate is small potatoes. The 14 million trees used in paper bags each year represent just one percent of the U.S. timber cut. The 12 million barrels of oil used to make plastic bags equal a small fraction of the gasoline our cars and SUV's use on trips to the store each year.

So, using canvas and mesh bags is best. If you're stranded without them, choose plastic. But to really help the environment, focus on larger issues -- like driving your car less and buying the car with the highest miles per gallon that will meet your needs. Walk to the store with your bag and you're batting a thousand!

Reference: Down to Earth Blog

Editor's Addendum: Great new graphic from the Washington Post, Oct. 4, 2007. "More Than Meets the Eye -- Paper or Plastic."