Not quite two years ago, the city of Portland decided to take the next step in its push to persuade residents not only to recycle, but to compost, as well. By one measure the move has been a success — garbage going to landfills has dropped by 38 percent, according to Oregon Public Broadcasting — but there are other, less pleasant ways to evaluate the program, unfortunately.

The program, which began in October 2011, requires garbage haulers to collect compost and recycling bins weekly. Garbage collection went to every other week, a money-saving move based in part on the notion that much of what makes the garbage can stink will instead be added to the composting bin.

That’s largely, but not completely, true. Dirty diapers are both smelly and not recyclable or compostable, and, unfortunately, are making their way into recycling bins at an alarming rate.

In fact, the company charged with sorting the city’s recycling is finding about 120 pounds per day of dirty diapers among the cardboard, plastics and other things its employees must separate by hand. That’s not only foul smelling and unpleasant, it can pose a distinct health hazard, as well.

Yet even that amount is an improvement. Just a few months ago sorters were gathering nearly 200 pounds of diapers a day, a situation so bad that the city began writing to homeowners who improperly put them in recycling bins.

City officials shouldn’t be surprised, nor should they rush to embrace the notion that diapers end up in the recycling because the garbage can is full. No doubt at least some are in the recycling because they smell so bad, and at two weeks old they smell even worse. Dumping them in the weekly recycle bin may not be an act of good citizenship but one driven by a desire to get the things out of one’s garbage can on a weekly basis.

All of which proves, yet again, that actions, even those driven by the purest of motives, can have unpleasant and unforeseen consequences. We wonder why those officials can’t offer, at a price, to be sure, to collect garbage weekly from folks unwilling to wait longer.