in honor of earth day.

PAPER OR PLASTIC?: It sounds like a big step forward in environmental awareness — Whole Foods, the eco-friendly grocery chain, will ban conventional plastic shopping bags in its 270 stores. San Francisco has banned them in some places; so have Uganda and Bangladesh. But paper bags, it turns out, are hardly an ideal replacement. To ensure sturdier bags, most producers use primarily new paper, which means cutting down more trees. Then chemicals are used in the production of the bags to give them strength. According to a study by Franklin Associates, a consulting firm, plastic bags require significantly less energy than paper over the course of their life cycle, from manufacturing to transportation. Indeed, because paper bags are seven times bulkier, on average, than plastic bags, it takes a lot more energy to transport paper bags to grocery stores. Bulk matters on the other end too: paper bags take up nine times as much room in landfills, and recycling plastic uses 91 percent less energy than recycling paper. Which isn’t to say that Whole Foods has it wrong about plastic bags. Most are made from a nonrenewable resource, petroleum, and contain their own mix of toxic chemicals. They may be more energy-efficient with recycling, but only about 1 to 3 percent of plastic bags are recycled, compared with about 10 to 15 percent of paper bags. And millions of the 100 billion bags Americans throw away each year end up as litter, clogging storm drains and choking sea animals. A third way may be the only good choice. As part of its ban on regular plastic bags, for instance, San Francisco is encouraging stores to switch to cornstarch-derived plastic bags, which break down in about a month and release no harmful chemicals. And many stores have started to encourage shoppers to bring reusable cloth bags, or to offer them for sale at a cheap price.