Jeff Sparrow

“Lambic is flat, since all carbon dioxide produced during lambic fermentation escapes from the barrel. Packaged young, lambic develops carbonation in a manner similar to a cask or bottle of real ale. Real ale is casked or bottled at the end of fermentation with just enough fermentable sugar left in solution to provide a gentle carbonation. The microorganisms responsible for lambic fermentation can consume virtually any type of sugar; therefore, the brewer never bottles young lambic. The fermentation of the remaining sugar in young lambic would produce enough carbon dioxide to shatter the bottle.”
― Jeff Sparrow, Wild Brews: Beer Beyond the Influence of Brewer's Yeast