With the addition of Northwest Philly, RecycleBank is now available city-wide. And David Biddle, the city recycling coordinator, says he won't settle for anything less than 100 percent participation.

Residents of Philadelphia are required to recycle anyway, and RecycleBank is the rewards program intended to boost participation.  The amount of recyclables put out curbside is measured on a community-wide basis, and then everyone in the community who has signed up gets reward points, which can be donated to a specific charity or local school project, or used for coupons at local and nationwide businesses.

The deal for the city is that they get more recyclables -- which they then sell. The amount is based on going rates, which are lower now, but in the past it's been $32 and more. In contrast, the city pays roughly  $63 a ton to take refuse to a landfill. So: A $95 differential per ton.

Some of the money goes to RecycleBank, which is a for-profit company, but officials say the math still works in the city's favor. And, they say, in yours.

The new RecycleBank program, which is also in place in many suburban municipalities, began in February and rolled out to a new section of the city every month afterward. Last Saturday, the city held a rally in Northwest Philly to welcome in the final section.

The city has 500,000 residences, and right now participation is about 60,000 homes -- or slightly more than 10 percent. Over the fiscal year that just ended, the city collected 99,445 tons of recyclables curbside. It's a record. In a matter of years, the city's residential recycling rate has climbed steadily from six percent, one of the lowest among the nation's big cities, to 17 percent.

I keep hearing rumblings that things are about to change yet again -- that the city is poised to start collecting not just No. 1 and No. 2 plastics, but also 3's through 7's.  At a press conference Monday about traffic signals, Streets Commissioner Clarena I.W. Tolson refused to confirm or deny it. But I would swear her smile was very close to a triumphant grin.  Stay tuned. I can hear the sound of two yogurt tubs (No. 5's) clapping.

Biddle, the recycling coordinator, is also a social scientist. And what interests him as he watches RecycleBank participation grow is trying to figure out when the tipping point will occur. At what point, for instance, will things reach a critical mass where people start talking at parties about the discount coupon they just received, or how the environmental project at their local school just got all the money it needed because so many people donated their rewards? At what point will it become part of the city lexicon, not just something people vaguely recall having heard about?

"Everybody wants to recycle," he said. But anecdotally, he hears that some just haven't had the time to sign up. Or haven't felt like figuring out one more thing in their lives. "People want to do the right thing," he said, "but activating their words is a little bit of a chore."

I can empathize. If I hear one more pitch for one more "customer loyalty card" that I've got to carry around in my wallet to get $1 off the next time I shop, well, I just don't know.

But I digress. Biddle says that signing up for RecycleBank enhances the whole conversation between city and residents.  The city gets information it needs about who's recycling what -- and just maybe, why. The residents get points for themselves and their neighbors. And so on.

"We have 500,000 households.,"Biddle says. "The goal is 100 percent participation, and I will not rest until I have that."

To sign up, go to www.phillyrecyclingpays.com or call 888-769-7960.