From the Sierra Club:
In New York City alone, one less grocery bag per person per year would reduce waste by 109 tons and save $11,000 in disposal costs.
Plastic bags carry 80% of the nation's groceries, up from 5% in 1982.
When 1 ton of paper bags is reused or recycled, 3 cubic meters of landfill space is saved and 13 - 17 trees are spared! In 1997, 955,000 tons of paper bags were used in the United States.
When 1 ton of plastic bags is reused or recycled, the energy equivalent of 11 barrels of oil are saved.
Reusing a bag meant for just one use has a big impact. A sturdy, reusable bag needs only be used 11 times to have a lower environmental impact than using 11 disposable plastic bags.
The solution? Canvas bags. I keep a stash in the trunk of my car, just in case I decide to run to the grocery store. They're reusable and washer friendly. A one time investment - even better!