Other "green" steps the store says it is taking include an attempt to reduce the use of plastic in its produce area. Customers are also invited to bring in their own reusable containers for things such as coffee beans or granola.

At Smith's Food & Drug, plastic is still offered, in addition to reusable bags and also paper, according to Marsha Gilford, vice president of public affairs. She said she understands that some people argue reusable bags are not eco-friendly, but her customers are asking for, and are using, the "green" bags.

Smith's tried to offer reusable bags about 15 years ago, but they did not sell, according to Gilford. The store tried again in 2007, and since then, sales have been continuous, she said.

"Our customers are seeking simple yet meaningful ways to contribute to good environment practices, and reusable bags offer that option," said Gilford.

Todd Jensen, sustainability coordinator for Harmons, said his customers have been quick to embrace reusable bags. His store has been offering a form of reusable bag since the early 1990s, but started issuing its current brand in late 2007.

Since then, at least 157,486 of the bags have been sold in Harmons' stores, and nearly 50,000 have been given away. The store estimates one reusable bag can eliminate up to five plastic bags with each use.

Jensen said he is aware of concerns such as Joseph's about the use of paper bags, but said Harmon's produces its bags in a very efficient, closed-loop system. At least 40 percent of the bags are made with post-consumer recycled content, he said.

From his perspective, anything a person can do to "reduce, reuse or recycle" is a big help to the environment.

"Reducing is a first step toward going green," Jensen said. "Using a green bag is a big help."

Green bags by the numbers

3.9 million fewer plastic bags were used by Harmons shoppers during 2008 as result of reusable grocery bags.

2.5 percent of Smith's shoppers each week receive a 5-cent credit for reusing their green bags or old plastic bags.

As result of recycling, Smith's saved at least 396,000 pounds of plastic from landfills last year.

At least 157,486 reusable bags have been sold by Harmon's since November 2007. The store has given away nearly 50,000 of the bags.

Whole Foods has saved 2.5 million plastic bags in its Rocky Mountain Region since last Earth Day.

As much as 80 percent of Whole Foods' reusable bags are made from recycled content.

What's happening this Earth Day?