Environmentalists hailed Toronto’s surprise decision to ban the standard plastic shopping bag.. But will banning the bag actually help the environment?
Probably, though the answer is somewhat more complex than council’s ban proponents have made it sound.
“It depends on a whole bunch of things in terms of how people respond to the ban,” says Mark Winfield, a York University environmental studies professor.
Many stores will probably switch to paper bags, which unlike plastic originate from a renewable resource, trees. They also break down faster, so they don’t linger as long as litter, and they don’t harm wildlife. But, as a 2006 British government study noted, the extraction and production process is the biggest factor affecting a bag’s environmental impact. Paper bags cause more harm during production.
“The pulping and bleaching processes involved in paper manufacture produce higher air emissions and waterborne wastes than plastics manufacture,” said a 2002 study for Australia’s government.
The British study concluded that, if 40 per cent of standard plastic bags are used to line bins, a paper bag would have to be used four times — which is not at all likely — to have less impact on global warming than a plastic bag. A 2004 study for the French supermarket giant Carrefour found paper bags at least 80 per cent worse than plastic bags for the consumption of water, emission of greenhouse gases and production of solid waste.
Major supermarkets and other big chains, however, are likely to switch to non-paper bags that are designed to be reused many times. It is these bags that will probably generate significant environmental benefits.
“A substantial shift to more durable bags would deliver environmental gains through reductions in greenhouse gases, energy and water use, resource depletion and litter,” concluded a 2007 study for an Australian state agency.
Toronto council approved a motion to ban only “single-use” plastic bags. Plastic bags built to last will stay legal. The British study found that supermarkets’ sturdy “bags for life” made of low-density polyethylene (LDPE) — as opposed to the light high-density polyethylene (HDPE) standard bags — were superior in eight of nine environmental impact categories if they were used a mere five times.
The Carrefour study, similarly, found that the heftier LDPE bags were better by every measure — including consumption of water, production of waste and greenhouse gases, and atmospheric acidification — when used a minimum of four times. And the 2007 Australian study found that reusable “green bags” made from polypropylene plastic were the best for the environment out of all bag options.
The Australian population in 2007 was about 21 million. If every household switched to such bags, the study found, the country would produce 24,000 fewer tonnes of waste and 42,000 fewer tones of greenhouse gases, and consume 1.4 million fewer gigajoules of energy per year.
No studies have been released on the durable bags distributed by Canadian supermarkets, but some may be even greener than the ones studied elsewhere. Loblaw, Canada’s largest grocery chain, makes its reusables from “99 per cent post-consumer recycled plastic bottles.”
Most bag studies rely on estimates of the level of reuse of standard plastic bags and the number of kitchen bags that would be purchased if the standard bags were no longer distributed. Ultimately, then, we won’t know what the environmental impact of Toronto’s bag ban is until we know how local shoppers and stores respond to it.
“If people move to using reusable bags, then in the long term we’re going to come out ahead. . . even better still if they’re made, for example, out of recycled material in the first place. Then the footprint starts to get very, very small per use. If people move to non-reusable paper bags, then, at least in terms of the energy and material inputs, it’s closer to a wash — at best,” Winfield says.