-By Phil Lempert

Please don’t misunderstand my position: I'm all for sustainability and protecting our environment. I just don’t believe that a tax levied by a city, state, or even the Feds will prompt most shoppers to switch to reusable bags.

Higher taxes on gasoline, cigarettes, and alcohol haven't done much to change behaviors, so why should it work on plastic bags?

One obstacle is the American shopper mentality that more is better. How often have you heard a shopper ask a clerk to double-bag their purchases, or to place just a few products in a bag so that they can end up with more bags, which presumably they're reusing for their trash, or to pick up their doggie's poop?

San Francisco's plastic bag ban is already in effect. Next January a Seattle ordinance will impose a 20-cent fee on disposable paper and plastic bags at grocery, drug, and convenience stores. Next up will be Los Angeles' plastic bag ban in 2010. Other cities and states are looking at similar legislation -- some banning plastic bags entirely, and some levying a tax that The Progressive Bag Affiliates of the American Chemistry Council estimates could cost grocery shoppers up to $400 per year per family. That, the trade group estimates, will add up to $400 million over the next 30 years.

How green is green?

Many food retailers have been quick to jump on the reusable bag trend, and are now selling (or giving away) bags emblazoned with their green messaging and logo. One Mid-Atlantic retailer I spoke with estimates that his chain alone has sold over a half a million bags in the first six months of this year.

I wonder, however, just where are these millions of "green" bags that supermarkets have already sold? I visit at least a dozen food stores every week, and I see few reusable bags actually being used by shoppers. The bags seem more prominent among shoppers at gourmet and health food stores than at traditional supermarkets. Is that a result of a typically smaller basket size? Or are these consumers more environmentally active?

My own concern is that many of the new "green" reusable bags are actually made from polypropylene (type 5 plastic), compared with the type 2 conventional bags supermarkets now use. Producing a bag with type 5 plastic actually uses an estimated 300 times more in resources, and such bags aren't generally recyclable.

In a recent 2008 NGA/SupermarketGuru Consumer Panel Survey, 79 percent of the more than 2,600 respondents said it was important for their supermarket to be active and involved in their community -- and topping the list of actions is protecting the environment.

When we asked whether our panel knew what a "carbon footprint" is, 60 percent said they did, and almost two-thirds reported that knowing the carbon footprint of individual items would make a difference in selecting what they purchase.

Soon after the plastic bag ban in San Francisco took effect, we surveyed our panel members from there and found that almost half of them had been either choosing plastic bags over paper (27 percent) or bringing their own reusable bag(s) (26 percent). Of this group, 85 percent said they believed that plastic bags had the most negative impact on the environment, vs. 15 percent who thought paper bags did.

When we queried them if they'd be willing to pay just five cents each for compostable plastic bags, the panel was split almost down the middle, with 53 percent saying they wouldn't be willing to pay for the more environmentally correct bags.

There's little doubt in my mind that until we can offer our customers a smarter alternative -- either a bag that's 100 percent degradable in a short time, or an incentive to choose reusable bags that won't have a greater carbon footprint than we have now -- little will change.

The cities that have an outright ban on plastic bags will certainly see a quicker shift in behaviors, but let's be realistic. Until the ban encompasses all plastic bags used in all stores (not just those that sell groceries), shoppers will be confused and unlikely to change their own personal carbon footprint.