The grocery-bag dilemma: Is paper or plastic greener?

But, alas, it was not to be. Researchers recently discovered that the supposedly green alternative actually harbours bacteria, mould, and other unappetizing and unhealthy organisms.

That we still lack a neat resolution to the checkout-line dilemma exposes a fundamental truth about all environmental issues: For every resource-use choice, trade-offs are inevitable.

Many governments have not considered the issue in any depth before issuing regulatory edicts in the name of environmental protection. Toronto, for example, passed a bylaw requiring stores to charge five cents for every new plastic bag in which groceries are packed. The mandated fee does not apply to paper bags even though these carry environmental impacts equal to or even greater than those of plastic.

Similarly, Leaf Rapids imposed a three-cent tax on single use plastic grocery bags in 2006, before banning them in 2007. The Liquor Control Board of Ontario has also banned plastic bags in its stores, but it allows paper bags.

Retailers are instituting bag policies, as well. Metro Inc., Canada's third-largest supermarket chain, plans to charge customers five cents per bag, just as grocery giant Loblaw's already does in Ontario. Whole Foods announced plans to discontinue the use of conventional plastic bags, although the store will sell upscale ones for 99 cents (or canvas ones for $6.99 to $35). It will continue to offer paper bags free of charge.

The effective endorsement of paper over plastic by Whole Foods and others has offended some green groups who justifiably argue that such moves lack an objective scientific basis. Steve Hamilton, president of the California-based Environmental Affairs Council, charges that Whole Foods and the like are engaging in "feel-good environmentalism at its worst."

Myriad factors must be considered when calculating the pros and cons, benefits and costs, of each bag type, including all the environmental and economic impacts of energy and chemical inputs and outputs in production, distribution, and reclamation.

Conventional wisdom holds that plastic bags -- being synthetic -- are environmentally destructive, while paper bags -- the spawn of trees -- are the greener option. But various life-cycle analyses of both products indicate that bags made from paper actually require more energy to produce, create more pollutants, and take up considerably more landfill space than plastic.

According to Progressive Bag Affiliates, a division of the American Chemistry Council, paper bags generate 70 per cent more emissions and 50 per cent more water pollutants than plastic, which requires 40 per cent less energy to produce and generates 80 per cent less solid waste.

Using plastic bags involves trade-offs, too. Earth Day Canada (2009) reports that the production of plastic bags involves five of the top six chemicals responsible for the greatest proportion of hazardous-waste generation. Moreover, most plastic bags are made from fossil fuels.

In their favour, paper bags are recycled at a higher rate than plastic, and require less energy to be recycled. They are biodegradable, although neither type of bag breaks down all that well in the dark, dry, and oxygen-deprived confines of modern landfills.

When exposed to ultraviolet light from the sun, the plastics will, over time, degrade into smaller particles. But they will not reduce to organic matter, as is the case with paper.

And not all reusable bags are created equal. For example, those made from polypropylene (plastic) are cheap to manufacture but wear out quickly, thereby limiting their reusability quotient. Canvas types are more durable, but cotton production is water-intensive and typically involves large quantities of pesticides.

Perhaps most troubling for consumers is the recent discovery that reusables pose a potential health risk, according to testing by two independent laboratories (and an evaluation of the results by a third). Researchers obtained the bags for testing from shoppers leaving major grocery stores. All the bags were tested on a blinded basis. More than 30 per cent of used bags had unsafe levels of bacterial contamination, 40 per cent had yeast or mould, and there were fecal bacteria in some. In contrast, conventional plastic bags showed no evidence of bacteria, mould, yeast, or coliforms.

Billions of grocery bags, both paper and plastic, are used and discarded annually worldwide. It should come as no surprise, therefore, that environmentalists would single out this particular waste stream as being ripe for corrective action. Some are capitalizing on it. Vincent Cobb, founder of Reusablebags.com, describes plastic bags as "a powerful symbol of consumerism gone wild." His website markets reusable alternatives that range in price from $4.95 to $18.95.

Opinions vary widely about the proper choice of grocery bag, and each has merits and drawbacks. That's all the more reason for governments to avoid dictating the choice, particularly when the elected officials doing the choosing are more intent on scoring green political points than actually improving the environment.

Diane Katz is director of risk, environment, and energy policy at the Vancouver-based Fraser Institute.

Republished from the Winnipeg Free Press print edition July 26, 2009 A11