Jorge Santiesteban estimates that food scraps constitute roughly 15% to 25% of what goes into black garbage bins in Los Angeles. The solid resources manager for the city has been struck by the seasonal changes in how much food we throw away ever since 1997, when a week after Thanksgiving, he had a garbage truck empty its contents for him. Santiesteban picked through the trash, putting like objects with like, until a clear picture emerged. This is what is known in recycling circles as a "waste characterization."

As bad as it must have been for Santiesteban during that November audit of rotting giblets and pie crusts, his San Franciscan counterpart might have had it worse. Waste characterizations done there show that as much as 30% of San Francisco's garbage has been composed of food scraps.

Now the race is on to see which of the two cities can divert more kitchen waste from garbage trucks to composting programs. With the introduction of mandatory food-scrap recycling in San Francisco on Oct. 21, the Bay Area has taken the lead.

The challenge began 20 years ago, when overflowing landfills led California to pass the Integrated Waste Management Act of 1989. This required jurisdictions to divert 25% of their trash to recycling programs by 1995 and 50% by 2000. If cities failed, they faced fines of thousands of dollars a day.

It soon became clear that not every city had the same trash profile. While Los Angeles produced huge amounts of lawn clippings, garbage trucks in the more urban San Francisco showed a higher proportion of food scraps.