When J.J. Shpall walked through a grocery store not long ago, he didn't see food on the shelves; he saw a problem.

"Something completely detrimental to the environment," the 16-year-old recalled Sunday before a bank of cameras and reporters.

Shpall saw bags. Lots and lots of plastic bags.

Shpall and fellow students from Kent Denver School are behind an effort to gradually phase out plastic bag use in Colorado.

A bill to do just that is being sponsored by Sen. Jennifer Veiga and Rep. Joe Miklosi, both Denver Democrats.

The two legislators, and more than a dozen Kent students, retreated from the raw, windy west steps of the Capitol to the rotunda to explain their concerns.

They want people to use cloth bags instead of plastic. Veiga said the bill would phase out plastic bags over three years at only the biggest retailers in Colorado.

The groups says 1 trillion disposable plastic bags are consumed each year in the U.S., requiring millions of barrels of oil to manufacture. They say it costs $4,000 to recycle one ton of bags.

San Francisco was the first city to ban the bags at large grocery stores and pharmacies, according to published reports. Other cities and grocers have followed suit or plan to do so.

But other communities have approved bag recycling programs instead after the plastics industry and its allies objected to bans, according to a report last March on MSNBC.com.

One company, 3B Bags of Highlands Ranch, displayed its new product at the Capitol news conference: a packet of three reusable mesh bags, which sell for $7.50.

Asked how low-income people will be able to afford such bags, company partner Amy Wade said that's a concern the company is in the process of addressing.

Veiga pointed out cloth bags can be found as low as $1 each, and they are reusable.