Is a “bag tax” coming to Maryland? The state taxes pretty much everything else, so it seems likely legislators will eventually get around to imposing a tax on plastic grocery bags. DC and Montgomery County are already doing it, and you know that if these jurisdictions have a bad idea, it’s going to spread to the rest of Maryland soon. This tax will be promoted as a tax to help the environment, but recent evidence indicates this is a weak justification for this tax scheme.

David Godow of the Reason Foundation points out that a new study suggests that plastic bags may stack up pretty well to reusable bags in terms of environmental friendliness:

A new study from the United Kingdom's Environment Agency casts doubt on this claim. In an analysis of the environmental impact of a smorgasbord of different bag types -- from conventional supermarket plastic to higher-grade polyethylene to cotton. Its surprising conclusion is that conventional plastic bags, because of their low cost and weight, had the lowest environmental impact in eight of the nine environmental impact categories studied. This assumes that bags are reused, for example, as trash can liners, about 40 percent of the time.

The authors also noted that the ostensibly eco-friendly cotton bag actually had a significant environmental impact. The authors chalked this up to the large amount of energy needed to produce cotton yarn as well as the fertilizer used to growth the cotton. In sum, they found a cotton bag would need to be used no fewer than 173 times to inflict as little environmental harm as its conventional plastic counterpart. The average cloth bag, according to the study, is reused about 53 times. Heavier, higher-cost reusable plastics also performed poorly.

The Philadelphia Inquirer had a story recently that talks about other problems with these bags:

Reusable bags were meant to supplant flimsy plastic grocery bags - the one-use, petroleum-based bags that critics say last for centuries and all too often wind up as litter or in the guts of sea life.

It's not clear the reusables have done that in any significant way. Indirect measures suggest that plastic bag production has remained relatively steady.

What is clear is that reusables have taken off as a cultural phenomenon, social statement, and even art form.

And, some worry, not all to the good.

"People are accumulating too many of these, so we're back to the original problem," said Vince Cobb, a Chicago businessman who reinvented himself as a reusable-bag expert and salesman at www.reuseit.com.

"The whole thing is to consume less," he said.

So he was appalled when the Chicago Bears gave away 40,000 reusable bags at a 2009 game. Many were thrown away by halftime.

If reusable bags aren’t the environmental silver bullet once thought, then why the push to tax plastic bags? The clue can be found in the Inquirer article – reusable bags are trendy; plastic bags are unstylish. It’s just “wrong” to use plastic bags, think some people, regardless of the actual environmental impact of these bags versus reusable bags.

Taxing plastic bags may fit well into an environmental narrative that certain legislators have. It may make them feel better about themselves, even if it won’t help the earth. But for many of us – those who actually reuse plastic bags for things like carrying lunches or disposing of dirty diapers – it will simply mean higher prices and more wasteful shopping habits. Is this the type of thing legislators really want to encourage?