Consider both risks and benefits of using plastic bags

The debate about plastic bags has taken a prominent place in the Durango news in the last couple of weeks after a majority of City Council members announced they would vote for a 10-cent charge on each paper and plastic bag used by customers at selected stores in order to reduce the bags’ presence in Durango’s environment. The response has been contentious because the council members have not demonstrated convincingly that the risk to the environment is great enough to counter the benefits provided by the bags.

Rather than dictating that the 10-cent charge be enforced, the City Council should address the issue as a benefit/risk trade-off because it is those benefits and risks that the public must weigh in order to judge the validity of the council’s action. Instead, the council members have ignored the benefit side of the equation and exaggerated the risks. I will address risks in a moment and start the discussion about the ignored benefits.

Anyone observing the checkout counters at City Market or Albertsons and witness the large number of customers taking home their purchases in paper or plastics bags can’t easily dismiss the conclusion that there are significant benefits involved. Convenience is a strong benefit, and bringing one’s own bags is not nearly as convenient. But the council seems to believe that a thousand signatures on a petition against plastic bags is more representative of people’s opinions than the empirical evidence observed at checkout counters.

It would be wise for the council before taking final action to find out how the majority of residents feel about the issue. Because Durango is the shopping center for much of the region, a countywide assessment would be in order for the sake of Durango businesses. There are several competent survey organizations that can provide a statistically valid assessment of the views of the population of Durango and La Plata County quite cheaply and in a short period of time. Obtaining a representative view of the importance of the benefits provided by the bags is critical because the evidence of their risk to the environment is weak.

There have been few scientific investigations of what happens to garbage making it difficult to formulate an evidence-based risk assessment, so myths and anecdotal speculations dominate discussions. The University of Arizona started a garbage project several years ago and is the only systematic hands-on analysis of the issue I know of. The results were published in a book Rubbish! The Archaeology of Garbage by William Rathje and Cullen Murphy, and the findings dispel much of what some Durango City Council members and letter to the editor writers seems willing to believe takes place with garage disposal.

One claim is that reducing the use of plastic bags will significantly reduce litter. But the bulk of litter consists of bottles, cans and paper cartons and reducing the number of only one kind of plastic bag from only selected stores will be undetectable. Furthermore, the University of Arizona study shows that almost all litter eventually, one way or another, ends up as garbage in a landfill. Which brings us to the most common complaint that plastic bags are filling up our landfills and contributing to the need for more.

The Arizona study shows that plastic bags of all kinds take up only a minuscule space in landfills. Beyond space, the concern seems to be that plastic bags do not biodegrade. But the study shows that nothing, not even food, biodegrades in a landfill. The book devotes a whole chapter to “The Myths of Biodegration,” why it doesn’t happen in landfills and why it would not be desirable if it did.

The Arizona study also destroys the myth that we are running out of safe places to put landfills. The book reports economist C. Clark Wiseman’s calculations that, given reasonable future projections, all of America’s garbage for the next century would fit into a single landfill space of 120 feet in depth and 44 miles square. It is not presented as a practical suggestion, but to make the point that not a lot of land is required to meet landfill needs.

Finally, some council members and letter writers have resorted to the rationalization that the 10-cent charge will make Durango a better community by alerting people to environmental issues and motivate them to take more actions against pollution. That is an unbelievably naive assumption. The recent book Nudge by University of Chicago economists shows evidence that some subtle inducements can work to change or motivate behavior, but overt pressure almost always has the opposite effect.

A 10-cent fee on each bag is not a subtle nudge but a sledgehammer blow. All that it is likely to do is to anger a segment of the population without any significant improvement to the environment. Determining how large that angered segment might be should be of interest to council members before taking any action because they may need to recruit many of them as allies when they address more important issue such as parking, water, energy and land use.

Garth Buchanan holds a doctorate in applied science and has 35 years of experience in operations research. Reach him at

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