Which is better? Not a simple question
Would you like paper or plastic?
Wait, that's not the right question any more.
Would you like 40-percent post-consumer recycled paper or biodegradable plastic? How about 100-percent recycled paper or plastic made from 80-percent post-consumer recycled bottles?
The environmentally correct choice would be none of the above -- because you brought your own reusable bags.
But deciding how to carry your groceries home from the store is more complicated than it ever has been before. Consumers -- if they care -- will be faced with these dilemmas as Honolulu and Maui counties consider laws banning conventional plastic checkout bags.
At most supermarkets in Hawaii, you won't even be asked -- your groceries will be shuffled quickly into plastic bags as they're rung up at the cash register.
On the face of it, plastic would seem to be the environmental evil -- made from petrochemicals, responsible for choking up marine life, clogging the waterways, and taking forever to break down.
In the oceans, plastic can drift and end up swallowed by birds, turtles and other marine wildlife, making its way into the food chain. Bits of plastic found in the stomachs of Laysan albatrosses at Midway are a prime example.
But paper isn't necessarily the better choice.
Paper bags mean trees were cut down somewhere, and energy expended to transport and manufacture them.
The Energy Information Administration (the statistics arm of the U.S. Department of Energy) says it takes 20 to 40 percent less energy to manufacture plastic grocery bags than paper ones.
Since plastic is lighter, it is more efficient to transport, says the EIA, while the delivery of the same amount of paper would require seven more trucks.
Biodegradable bags made of cornstarch seem like a better choice, but at the same time, they require air and light to break down, which is not likely in a landfill. Growing corn also requires energy that would need to be calculated into its carbon footprint, according to environmentalists.
The Sierra Club contends that paper is easier to recycle, but that reusing bags is still the best choice. The recycling rate for plastic bags is very low, at 5 percent at best in even the most environmentally conscious cities.
Calculating the carbon footprint of paper versus plastic is difficult because of all the variables, according to Darvy Hoover, senior resources specialist at the Natural Resources Defense Council.
"You can say, 'Neither,' whenever possible, because both types of disposable bags have environmental consequences that can be avoided," he said. "But if you need to take a disposable bag, then take the one you are more likely to reuse."
Between a conventional plastic bag and biodegradable plastic bag, he said the latter was a better choice because it's a renewable material.
The bioplastics industry, on the other hand, is still young, with room for improvement.
As a general rule of thumb, Hoover says recycled paper bag is better than a regular paper bag. He said San Francisco's bag law is a good model to follow because it requires that paper bags be made up of at least 40 percent post-consumer recycled content.
The best solution, of course, is to bring your own reusable bags to take those groceries home.