Where do all those rotting jack-o-lanterns go?

Right now, somewhere on your block, a pumpkin is rotting. If you’re lucky, that somewhere is in a Waste Management-sanctioned green bin, where it can safely decay with other compostable trash, and not on your front porch. It is mid-November, after all.

This time of year, pumpkins become a major player in the composting program run by Waste Management, the North American company in charge of trash in Alameda County. In Oakland, all degenerate Jack-o-lanterns — as long as they are properly discarded in one of those green bins — will be fetched by a WM truck and driven to the Davis Street Resource Recovery Complex in San Leandro.

From there, they head to different facilities around the state, where they will simmer among tree branches, soiled paper plates, and bacon fat for three months, emerging triumphantly as compost, which is then sold in bags or by the truckbed-load at Davis Street.

Waste Management started its Bay Area-based EarthCare product line of compost and mulch in Alameda County in 2005. The local system has been so successful that Davis Street now serves as a model for other facilities across the country. Just last week, a group of Waste Management employees from Florida visited the San Leandro complex, hoping to learn how to replicate the EarthCare line in the Sunshine State. They’ve got plenty of pumpkins down there too.

According to Rebecca Jewell, the recycling program manager at Davis Street, different fruits and vegetables tend to dominate at different times. Pumpkin season may be over, but persimmons are thriving, and your neighbors’ fig tree prospers in June and July and again in September and October, and so on. That leads to surplus and that surplus ends up in Waste Management bins.

Currently, you can spot dashes of orange in the waste piles at the complex’s LEED-certified transfer center, which processes anywhere from 200 to 500 tons of green material each day.  Even now, at peak season, pumpkins make up less than 2 percent of all the green waste the facility recycles, Jewell says, but she still considers them a boon.

For one thing, they hold a lot of water, which helps the microbes involved in composting get the nutrients they need. They’re also high in nitrogen, one of the most important elements needed in composting. That’s why a pumpkin will rot within days of being severed, and one left untouched can last for months. “Once you cut into a pumpkin, you’ve basically unwrapped it…and everything [the microbes] need is right there to begin the decomposition process,” she says.

According to Jewell, the site tends to get more waste in the spring and early summer, and less in the fall and through the rainy winter. November got a little bump from the pumpkins, but once the gourds are gone, it’s slow rolling once again. Until, of course, the holiday season is over and the Christmas trees start rolling in. “Christmas is another fun time, because then the whole site smells like a car scent,” Jewell says.

Though the current batch of pumpkin-laced compost won’t be ready until early next year, there’s a big pile of the brown stuff from this summer at Davis Street right now waiting to be deployed in your home garden – and also bought up by larger customers like CalTrans, which has used compost for erosion control. (The average family generates 2,400 gallons of compostable material a year, Jewell notes — far more than even the largest home garden could absorb.)

But it’s the farmers who are especially important to the composting system – both by growing the produce that eventually ends up in green bins, and by buying much of the compost that Davis Street produces.

In the end, it’s a closed loop. If you put that uneaten cauliflower you bought from the farmers market into your green bin, it will most likely end up back with the farmer you bought it from — as compost.

“It’s like an Elton John song,” Jewell says. “The circle of life.”

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