(BizJournals) - Christopher Silva, a fifth-generation Sonoma County native, is big on sustainable agriculture and "green" alternatives. So back in 2013, he decided to stop using synthetic wine bottle closures on virtually all of his company's wines and return to the natural solution: Cork.

And he hasn't looked back.

Silva's company and other Bay Area wineries that experimented with synthetic stoppers and screw-tops for win bottles have started switching back to cork.

Nationally, Nielsen data shows that over the last five years cork closures have accounted for most of the growth among the top 100 premium wine brands in a survey covering all major U.S. metropolitan areas. As a result, wines with cork closures had 59 percent of the market for those wines as of May 1, 2015, compared to just 50 percent five years earlier.

St. Francis Winery & Vineyards, where Silva has been president and CEO since 2003, has a Santa Rosa mailing address and a winery in nearby Kenwood. It produces 200,000 cases of wine a year, all but a tiny fraction with cork closures.

The biggest segment — at roughly 80 percent — of the total is its Sonoma County brand, which includes chardonnay, cabernet sauvignon, merlot and "old vines" zinfandel. But St. Francis also sells higher-end reserve wines that retail for $90 to $110 in restaurants, and just introduced a $40-$50 Artisan line.

All but 6,000 cases of sauvignon blanc and small batches of other varietals now come topped with natural cork, after two decades of using synthetic substitutes.The winery continues to sample other closures.

The winery's founder, Joe Martin, switched to synthetics in 1993, weary of dealing with cork taint issues. But by 2013, Silva told me Thursday, technological advances in growing cork and culling the best material, plus improved sorting and testing techniques, had eliminated much of the taint problem.
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So he shifted the winery's main Sonoma County brand back to cork, which he calls the "biodegradable, sustainable" choice.

Others are making the same move.