What’s in the Bag?

Photo by Laura Poppick

We all have our reasons for choosing paper vs. plastic vs. reusable bags. A woman at a checkout line in Alabama told a friend of mine that she uses reusable bags because she would rather see petroleum go into NASCAR races than plastic bags. Like I said, we all have our own reasons.

With recent plastic bag bans across the Central Coast — including San Francisco, San Jose, and now Santa Cruz — our checkout choices are narrowing. Some wonder if this is a good thing. Paper bags are roughly nine-times heavier than plastic bags. The extra weight calls for that much more energy in manufacture and transport. A selling point for paper is its biodegradability, but isn’t plastic becoming more biodegradable? Are we prematurely banning plastics when they are ready to break down?

Made largely from cornstarch, these evolving ‘bioplastics’ theoretically sound like viable alternatives. They have become popular around the world, particularly in Italy where conventional plastic bags have been banned nationwide since January 2011.

But Italian researchers are finding that these bags, like their petroleum-based predecessors, still stubbornly resist degradation in a variety of environments. In the September Journal Chemosphere, researchers at the University of Bologna reported the rate of bioplastic degradation in four different environments: soil, compost, freshwater, and saltwater. They found that, in soils that supported the fungus and bacteria that break down the bags, bags disappeared completely after 3 months. But under poorer soil conditions, they broke much more slowly, and hardly changed at all in fresh and salt water.

Since a major premise of the bag ban is protecting marine life, this finding does not bode well for bioplastics.

Illustrated by Laura Poppick

A separate Italian report published in the June Frontiers in Microbiology addressed another complexity of this issue: once a bag enters the water, does it stay floating, or does it sink to the seafloor? The research team wondered if bioplastic bags would degrade faster if they got stuck in the sand. They found that, indeed, bags buried under sand did break down faster than those floating at the surface. But whether a bag sinks or floats depends on winds, currents, and other factors that complicate how many bags ultimately break down on the seafloor.

While new technologies are certainly improving the biodegradability of plastics, the plastic market does not seem primed to shake off stigmas of littered oceans and clogged sea turtle lungs. Paper, which is more degradable but also more resource intensive, might not be a much greener alternative. So are reusable bags the way to go?

Mark Daniels, chairman of the American Progressive Bag Alliance, says no. Sure, maybe his affiliations sway him, but he just doesn’t feel comfortable using reusable bags. They can harbor hazardous bacteria, he told the New York Times last month, and he will not get in line behind someone at a store using a reusable bag because he worries it might carry bacteria that the cashier could spread to his food.

Bacteria can be dangerous, but dangerous bacteria is everywhere. If we’ve lasted this long without disposable socks, we can probably make reusable bags work. The easiest and best choice to make during the plastic bag ban might be to take out our smelly reusable bags, wash them, and try to remember to bring them to the store.

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3 Responses to What’s in the Bag?

  1. Chris Palmer 25 October, 2012 at 7:55 pm #

    Laura, great post! I love the illustration and the title.

    • Laura Poppick 29 October, 2012 at 8:01 pm #

      Thanks Chris!

  2. Robert Irion 4 November, 2012 at 10:12 pm #

    I agree; the illustration is a nice touch. I’d love to see many of your blog posts enhanced with some original art — good practice for Science Notes and the multimedia class!

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