Good Fruit Grower

April 15

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16 APRIL 15, 2015 GOOD FRUIT GROWER Walla Walla Community College hopes to show wineries how to compost their wine leftovers. by Melissa Hansen O ne way to deal with winemaking leftovers is to turn it into compost. But as Washington State's Walla Walla Community College has found, transforming grape pomace into compost required trial and error before perfecting the composting technique. After every crush, wineries are left with the skins, pulp, seeds, stems, leaves, and other residue from winemaking after the juice has been pressed and fermented. Uses for pomace include turning it into grape-based wine or distilled products, using it for cattle feed, recycling in vineyards as mulch, or turning the seeds, skins, and pulp into consumer products like grapeseed oil, flour, and material for biofuel digesters. But many wineries send pomace to landfills. The composting project at Walla Walla began last fall with grape pomace from the college's teaching winery. "We're finally perfecting our pomace-composting process," said Dave Stockdale, who's in charge of the compost project and is director of the college's William A. Grant Water and Environmental Center. The center, Grapes Turning pomace PHOTOS COURTESY DAVE STOCKDALE Dave Stockdale with a sample of compost made from grape pomace—the skins, pulp, seeds, stems, and other winemaking leftovers. A field day is planned later this year to share results of the composting demonstration project. COMPOST which opened in 2007, is a facility where education, research, and collaboration play key roles in addressing issues related to the sustainability of southeastern Washington's water-dependent agriculture, salmon- runs, and overall economy. The center offers degrees in water resources technology, irrigation technology, and watershed ecology. Stockdale shared successes and failures of the proj- ect with winemakers during the annual meeting of the Washington Association of Wine Grape Growers. The project was designed as a case study in hopes that other wineries can learn from the college's mistakes and suc- cesses. A field day is planned for later this year to show results of the composting study. The composting technique under study is the aerated static pile method, supposedly one of the simplest and least costly approaches to composting large volumes. Composting grape pomace —Three tons of grapes will yield about one ton of pomace. —Pomace is made up of about 8 percent seeds, 10 percent stems, 25 percent skins, and 57 percent pulp. —Pomace is rich in nitrogen, potassium, and calcium. —High lignin in seeds limits decomposition in unturned piles. —Feedstock added to pomace should have a calcium-to-nitrogen ratio appropriate for composting (1:20 to 1:30). —Piles with greater than 60 percent moisture may continue to ferment and produce acetic acid. —Composting can be a six- to ten-month process, depending on turning frequency, moisture, and temperature of piles or windrows. SOURCE: VIRGINIA TECH into

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