Seattle Public Utilities, which manages solid-waste collection in the city, mailed letters to 800 homeowners this week to alert them that they would be part of a pilot project starting July 1 and running through December.

Free, unlimited recycling will still be every other week. Food- and yard-waste collection will remain weekly.

Participation in the pilot program isn't optional, but the city will reimburse all the study households $100 to offset any inconvenience and for the cost of a larger garbage can, if needed.

The city plans to study how people respond to less-frequent collection and whether it encourages greater recycling and composting.

Every-other-week garbage collection could save $6.4 million a year in operations as well as reduce truck traffic and carbon emissions, the city says.

The utility also plans to test two rate schedules. In both, the cost of a 32-gallon can would drop by a few dollars with every-other-week pick up. The cost of a larger, 64-gallon can would go up by about $3 in one trial and $12 in another, to see if cost makes a difference in overall waste reduction, recycling and composting.