When Concord Co-op decided to stop using plastic bags at the checkout counters, the idea was to make some physical improvement in the environment. Turns out, it has made some mental improvement, too.

“It has changed the mindset of people going through the store, it really has,” said Chris Gilbert, general manager of the Main Street store. “A lot of people come in and buy one small item and used to say, put it in a bag. Now they are going, ‘oh no, I don’t need (a bag), I’ll just carry it.’”

“It’s not even something you’re conscious of: ‘Yeah, just throw it in a bag.’ Now, it’s ‘Do I really need a bag for that one bottle of vitamins? Can I put it in my pocket?’”

Gilbert says that since the switch on Jan. 1 the store has gone from giving out 2,800 to 3,000 plastic bags a week to about 700 paper bags. More people are also bringing their own, reusable bags — including a version that the Co-op sells — or using empty cardboard boxes that the Co-op makes available.

The reduction in bagging is due to another factor: The Co-op gave plastic bags for free but charges 10 cents per paper bag. Even if that’s not enough cost to make customers balk, it gives pause that can make people rethink whether a bag is necessary.

The 10 cents helps offset some of the extra cost of paper, Gilbert said. The previous plastic bags cost $70 a case while the same number of paper bags is $189. Even so, the lower usage means the company’s costs are about the same.

The environmental benefit of making paper bags rather than plastic is debatable. A 2011 research paper said it takes 4 times as much energy to produce a paper bag, comparing the cutting and processing of trees into paper to the drilling of oil and production of plastic and noted that transportation costs are higher with paper bags because they’re much heavier. On the other hand, trees are renewable in a way that petroleum isn’t.

After usage, however, there’s no contest: Paper rots and enters the environment relatively quickly but plastic, even compostable plastic, remains for decades or centuries, breaking into smaller pieces but not disappearing. Microplastic fills the ocean where it enters the food chain; recent research has found it regularly showing in people’s bloodstreams, with unknown health effects.

There’s even a visible benefit to the switch, Gilbert noticed. “You don’t see paper bags blowing down the street or getting stuck in the woods, like plastic bags.”

Gilbert said the Co-op is trying to eliminate plastic entirely in selling food to customers, pointing to the switch away from plastic containers at its hot food bar and switching to paper bags in its bulk-food department. If you buy vegetables, though, wetness-resisting plastic bags are still the store option.

“Produce? Not yet, because of the moisture,” Gilbert said.

“The goal is to eliminate plastic; it’s going to take some time, but that is the ultimate goal.”