PORTLAND, Ore. — Stephanie and Matt Murphy plan on using cloth diapers instead of disposable ones once their first baby arrives next month. They want to be good environmental citizens and reduce what they send to landfills, but there is another incentive, too.

“It’ll be nice not to have it sitting out there in the trash,” Ms. Murphy said. “That’s the main reason we’re doing it: to improve the odor of Portland.”

Just when their infant girl is due to arrive, Portland will be experiencing its first summer of biweekly garbage pickup. The change to every other week, introduced in cool weather last fall along with a weekly collection for food scraps, has reduced the amount of garbage that this progressive city is shipping to landfills by 44 percent.

The experience has not been entirely smooth. Since the garbage pickups were spaced out, the city’s main recycling company has complained that more garbage — disposable diapers included — is showing up in recycling bins. Residents complain about strong smells from garbage that has stewed for two weeks in the driveway.