One of the new environmental trends sweeping local governments is the push to ban plastic grocery bags. The argument is that such bans protect wildlife by preventing the bags from getting into the water. This is just one of a range of claims about plastic bags and the environment, many of which are false or exaggerated. Here is a quick rundown of the claims about plastic bags and the actual data and science.
Plastic Bags Contribute to a Massive Garbage Patch in the Ocean
This is a common claim and one of the first arguments mentioned by advocates of the ban. It is, however, almost entirely false. While advocates say the Pacific Garbage Patch is about “twice the size of Texas,” the fact is that what does exist is much smaller. Angel White of Oregon State University released a statement last year noting “The amount of plastic out there isn’t trivial. But using the highest concentrations ever reported by scientists produces a patch that is a small fraction of the state of Texas, not twice the size.” She went on to say “There is no doubt that the amount of plastic in the world’s oceans is troubling, but this kind of exaggeration undermines the credibility of scientists.”
Woods Hole Oceanographic Institute echoed this conclusion in a study that found “the concentration of floating plastic debris has not increased during the 22-year period of the study, despite the fact that the plastic disposal has increased substantially.”
This doesn’t argue that plastic in the ocean has zero impact, but it provides a basis for understanding how best to address the real extent of the problem.
Plastic Bags Kills Thousands of Marine Animals
The obvious implication of the claim about garbage in the ocean is that it will harm marine life. One such claim was included in a packet for a city council in Washington state considering a ban. City staff claimed “the ecological impacts of this plastic include over a million sea-birds and 100,000 marine mammals killed by either plastic ingestions or entanglement.” This is simply false and the National Oceanic and Atmospheric Agency (NOAA) has debunked this one thoroughly. On their FAQ regarding plastic bags, NOAA writes “We are so far unable to find a scientific reference for this figure.” They go on to speculate the number comes from another source relating not to plastic bags but to “to active fishing gear bycatch and not marine debris.” Banning plastic bags does nothing to address this problem.
As a side note, there is a serious problem with lost fishing gear — nets that continue to kill even after they have been lost. Confusing that real problem with unscientific claims about plastic bags, however, is dishonest.
Reusable Bags are Better for the Environment
The reason grocery stores moved to plastic bags is quite simple: they cost less. One key reason is that they use less energy to produce. Substitutes all use much more energy. Paper bags, for example, use about four times as much energy as plastic bags. Environmental activists often point to reusable bags as the preferred alternative, but research shows this is far from a panacea. For example, one study completed by the U.K. Environment Agency found reusable cotton bags took 173-times as much energy to produce as plastic bags. Assuming one trip to the store a week, it would take more than three years of use simply to break even, energy-wise. That may be possible, but if people regularly wash their bags (as they should) it is questionable how well the bag would hold up. Banning plastic bags would eliminate the lowest-energy product in favor of high-energy alternatives, which would likely increase overall energy use.
Plastic Bags Aren’t Recycled
This is largely true but misleading. Fewer than ten percent of plastic grocery bags are recycled, whereas paper bags are recycled at much higher rates. The reason, however, has much to do with the environmental mantra of “reduce, reuse, recycle.” Although plastic bags are rarely recycled, they are frequently reused. The City of Seattle estimates that about half of plastic grocery bags are reused as garbage bags, to pick up after pets, and similar uses. As noted above, plastic bags also do well when it comes to the “reduce” calculation as well, reducing the amount of energy-per-bag. Banning plastic bags doesn’t eliminate the need for garbage bags or the other uses, it simply requires consumers to buy other bags. A ban would neither reduce nor reuse.
Banning Plastic Bags is a Net Benefit for the Environment
This is, to some extent, in the eye of the beholder. If you believe that reducing plastic in the ocean is a good thing at any cost, then you probably support bag bans even if they have little benefit. That, however, is a simplistic approach that ignores huge environmental costs (not to mention economic costs). We are constantly lectured that climate change is the most important environmental issue of our time, yet the energy costs of banning plastic bags are often ignored. Indeed, we can even estimate the environmental value of banning the bags to see if we are receiving the environmental benefit we pay for.
When the Seattle City Council proposed taxing plastic bags, The Seattle Times tallied the overall reduction in resource use that would result. The city expected to spend $10 million, projecting that water use for bag production would be reduced by 39 million gallons each year and would cut CO2 emissions by 6,000 tons per year (this does not examine the costs of replacing the bags which, as noted above, would likely increase emissions). These numbers sound large, but actually the impact is quite small. To put a price on the value of the CO2 reductions, we can use the European carbon market price of about $20. Reducing 6,000 short tons of CO2 would cost about $109,000, or one percent of the cost of the bag tax.
The numbers for conserving water are similar. Each day, Seattle uses about 130 million gallons of water. Reducing water use by 39 million gallons a year is less than one one-hundredth of one percent of water used in Seattle, or less than one-third of one day’s consumption. So, the amount of water saved by this tax would be infinitesimal. How much is that amount of water worth? Using residential rates, which have the highest marginal rates, the cost of 39 million gallons (5,213,904 cubic feet) is between $169,452 and $553,716 depending on the amount used, assuming use during peak times.
In other words, the bag tax would cost $10 million to gain environmental benefits that could be acquired for as low as $278,452.
Like so many trendy environmental ideas, banning plastic bags is a policy that fares quite poorly when examined with a rigorous economic and scientific approach. That, however, hasn’t stopped a number of jurisdictions from banning the bags, sending out press releases proclaiming their commitment to saving the environment, and encouraging other cities to follow suit. Ultimately, the bans are more about politics than the environment.