Thursday, December 4, 2008

Garbage to Gold

Our CSA newsletter gets down and dirty this week, looking to see what happens to your fruit after you're done with the good parts. The inspiration for this essay came from one of Farmer Al's customers at the Ferry Plaza Farmers' Market, who pointed out that all the food scraps collected at the Ferry Building were composted at Jepson Prairie Organics in Vacaville.

As it turns out, one of Frog Hollow's biggest compost suppliers is Jepson Prairie. Every week, according to their website, some 5000 tons of food scraps from Bay Area homes and businesses are trucked out to their site in Vacaville for composting. As a subsidiary of Norcal Waste Systems, Jepson gets all the orange peels, old lettuce, leftover spaghetti and half-eaten burritos that the Bay Area tosses into its green-waste recycling bins. This admittedly stinky but valuable sludge gets minced on-site, since the smaller the pieces, the faster they decompose.

This makes up what home composters know as "greens"--the soft, leafy, juicy stuff that's high in nitrogen and breaks down quickly. What a good compost pile needs is a balance of "browns", too--drier, harder materials, like straw, wood chips, and dry leaves, that are high in carbon and slower to break down. So, Jepson Prairie mixes in yard & tree trimmings from Vacaville and Dixon to get the proper ratio of brown (carbonaceous) and green (nitrogenous) materials.

Then, the mix goes into self-contained plastic pods known as "Ag Bags," which are threaded with aeration pipes. The mixture starts breaking down and in the process heats up to temperatures sufficient to kill pathogens, undesirable bacteria, and weed seeds. After 2 months in the "Ag Bags," the mixture goes outside, piled in long, tall windrows. These windrows are mechanically turned numerous times during the next 30 days to keep oxygen moving throughout the pile. After 30 days, the black-brown, crumbly, and nearly odorless mixture is screened to sift out any oversized pieces. Once it's been sifted into a uniform mix, it's ready to go out to the farm.

Just like the city that feeds it, much of the value of Jepson Prairie's compost comes from the diversity of its sources--everything from coffee grounds and pomegranate rinds to pad Thai and persimmon peels.

So, toss an apple core into your green recycling bin and it can end up right back in the orchard, in the form of lush, microbe-rich compost that enriches the soil and feeds the trees.

And speaking of green garbage at the Ferry Building, Gov. Schwarznegger just gave the marketplace a 2008 Governor's Environmental and Economic Leadership Award. Check it out in the Chronicle's City Insider column, which mentions the building's composting program as a way of "closing the loop" between urban-edge farmers and city consumers.

In case you were wondering, no, you can't buy Jepson Prairie's compost for your backyard. As a wholesale operation, they sell only to farms, nurseries, wineries, and other businesses with commercial resale licenses, not to private individuals. If you'd like to learn more about backyard composting, check out these classes from San Francisco's Garden for the Environment.

1 comment:

Julie Cummins said...

You can see photos of the composting process at Jepson here
They no longer use the ag bags described on the website; they just use covers instead. I love the idea that we could eat a Frog Hollow pear at the Ferry Plaza Farmers Market, throw the core in the green bin, and it could end up back on the farm under a pear tree!
-Julie of CUESA (the nonprofit that manages the Ferry Plaza Farmers Market)

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