The wine we pour feels as natural as air – and it is – but even nature has a way of turning on itself when human activity gets involved. In the case of Monterey County’s air quality, the naturally occurring process of fermenting wine is a big contributor to emissions of volatile organic compounds, or VOCs, into the atmosphere, where they can create ozone pollution.
Large-scale winemaking operations in South County emit more VOCs annually than the Dynegy power plant in Moss Landing, says Richard Stedman, air pollution control officer for the Monterey Bay Air Resources District.
As picking and crushing grapes begins in late summer and the fermenting process begins, yeast converts the grapes’ sugars into ethyl alcohol, also known as ethanol, and carbon dioxide, both harmful to the atmosphere in large quantities. To meet federally mandated air quality standards, the district set limits on how many VOCs wineries are allowed to emit daily as well as annually.
The county’s largest winery, the New York-based company Constellation Brands, Inc., releases over 100 tons of VOCs annually from industrial-sized tanks resembling oil refineries, Stedman says, “so this is not inconsequential stuff.”
As of now, Monterey County’s wineries fall within emissions limits but the limits are stunting future industry growth, says Kim Stemler, executive director of the Monterey County Vintners and Growers Association. At least two large wineries Stemler declines to identify have said they won’t come to the county unless the VOC limits are increased. Those limits also lead some large wineries to ship grapes out of the region by truck for crushing, leading to carbon dioxide emissions from transportation. “It’s a net bad,” Stemler says.
Stedman suggests winemakers could use devices to capture VOCs. The industry is slow to embrace that technology, fearing a negative impact on wine quality. (Assembly Bill 1714 is pending in the State Senate and would allocate $1 million for the study of air emissions from wine fermentation tanks and the impacts of such control devices on wine.)
Meanwhile, Stedman is working with winemakers to possibly increase VOC limits. The district air district board of directors will hold an informational meeting on Feb. 19 to consider whether to take action. If the board decides to increase the VOC emissions cap, the air district could face barriers to approval before the California Air Resources Board, where local districts are prohibited from “backsliding” or enacting less stringent rules without going through a strict process.