“Eco-Friendly” Reusable Bags Not So Green After All?

Washington, D.C.’s first-in-the-nation tax on plastic bags has spawned a wave of eco-enthusiasm that’s seen 64 similar measures pop up across the country in 2011 alone. Tax advocates argue that D.C.’s measure cut plastic bag consumption and reduced the amount of discarded bags found in the polluted Anacostia River.

Plastic bag tax advocates often encourage the use of reusable bags made from natural materials like cotton, hemp, or jute. They claim replacing disposable, plastic bags with sturdier, longer-lived cloth or plastic will save resources, limit pollution and curtail litter on streets and in waterways.

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 standard supermarket shopping bag may not be particularly fashionable, but we shouldn’t overlook its potential economic advantages over its glitzier, more “eco-friendly” alternatives.