Patrick Swanson has launched a covert operation to rid his house of reusable shopping bags that his wife keeps bringing home from the grocery store. He brings a bag over to a friend’s house and, when no one is looking, “forgets” it there.

“The idea of the reusable bag has merit, but my opinion is that the majority of people forget to re-use them,” the St. Paul resident said. As a result, “they pile up. ... We never re-use them. In fact, I think we have more ‘reusable’ bags in our closet than the old paper and plastic kind.”

Swanson is far from alone in wondering if reusable bags sound better in theory than in practice. There’s an increasing pushback against the bags, with critics arguing that when you factor in the way the bags are used — or, in this case, not used — they actually have a larger carbon footprint than the plastic variety. But members of the green movement still staunchly believe in them, arguing that the cloth versions keep landfills free of millions of plastic bags, which can take up to 1,000 years to decompose.

Even among naysayers, support for reusable bags continues to grow: 39 percent of grocery shoppers own them, according to a recent study by McOrr Research.

But are shoppers using the bags enough to make them worthwhile? The UK Environment Agency recently concluded that a cotton bag has to be used 131 times to equal the environmental impact of producing one plastic bag.

Supporters of reusable bags have rushed to their defense.

“Yes, there’s energy embedded in the making of those bags,” conceded Madalyn Cicoi, a waste prevention and recycling specialist for the Minnesota Pollution Control Agency. “The goal is, once you get the bag made, to get as many uses out of it as you can.”

Of course, they don’t help the environment if they’re piling up in a closet.

“There’s no need to collect more of them than you need,” said Cicoi, who carries her groceries home in two cotton bags that she bought in 1995. “The whole point is to use them all the time.”

Some people who end up with a stockpile of bags find alternative uses: stashing Christmas decorations in them, using them to organize hobby gear or turning them into overnight bags.

“They are incredibly utilitarian,” said Sara Pearson, who now lives in Richmond, Va., and still uses bags she got in Minnesota six years ago.

Paper, plastic or bacteria?

Reusable bags have come under attack before. When San Francisco banned plastic grocery bags in 2007, the Social Science Research Network published a report claiming that reusable bags are breeding grounds for bacteria. The most alarming charge was that after the plastic bag ban went into effect, emergency room admissions related to bacteria jumped 25 percent.

The report was widely lambasted for not following accepted research procedures involving peer review, and follow-up research failed to come close to verifying the 25 percent figure. But the report was enough to motivate other research, including a 2011 study of reusable bags in California and Arizona in which 51 percent of the bags examined had picked up bacteria from the food they carry.

The green community’s reaction? “Well, duh.”

“To wash something that you carry food in, that’s just common sense,” Cicoi said.

In fact, the same 2011 study, facilitated by Food Protection Trends, also found that washing the bags killed the bacteria.

“I don’t worry about it,” said Nancy Lo, who works on waste reduction and recycling for the Hennepin County Department of Environmental Services. “I just throw the bags into the washing machine.”

A jump in reusable use

Reusable bags, mainstays in Europe for decades, started making inroads into the United States around 1990.

“When they started showing up in mainstream places like Lunds, people realized that they weren’t just for tree huggers anymore,” Lo said.

Lunds and Byerly’s started selling reusable bags in 2006 and began tracking their use in 2009 via an incentive program in which the stores donate 5 cents to the Second Harvest Heartland food shelf for every reusable bag a customer brings into the store. As of last week, the stores had donated $220,000, which translates to 4.4 million reusable uses.

But lapses of memory hamper the bags’ use.

“That’s a big issue for us, getting people to remember to put the bags back in their cars after they unpack their food at home and then remembering to bring the bags into the store with them,” Lo said. “Just having the bags isn’t enough. People aren’t going to use them if they’re not convenient.”

Some grocery stores are posting reminder signs in the parking lot and on their doors. Hennepin County is making available free “Don’t forget the bags!” window clings.

“I have a sticker in my car to remind me to bring reusable bags into the store, because I would often forget,” said Mia Olson of Bloomington. “But eventually it becomes habit-forming.”

Sometimes, however, even the best intentions go awry. Laura Toledo of Minneapolis admitted that even though she and her husband try to keep bags in the trunk of their car and put a couple of spare ones on a hook by the kitchen door, they still occasionally arrive at the checkout stand empty-handed.

Rather than buy even more bags, they have a backup plan.

“If we do forget our bags, we’ll take plastic at the store and re-use them at home,” she said. “We never throw them away right when we get home. We’re trying to save the environment in as many ways as possible, even small ones like this.”