What type of beer fermentation uses wild yeast from the air, especially in Belgian breweries?

The correct answer is Lambic. Lambic beers are traditionally fermented using a method known as spontaneous fermentation, which involves the use of wild yeast and bacteria present in the environment. This process typically occurs in open vessels, allowing the wild yeast from the air, particularly Brettanomyces, to enter the beer. This unique fermentation method is characteristic of Belgium's Cantillon Brewery and other breweries that produce Lambic styles.

Lambics are distinct in flavor and aroma due to the presence of these wild organisms, which contribute to the sourness and complexity of the beer. This fermentation method sets Lambic apart from other beer styles, which usually rely on controlled fermentation using specific strains of yeast. The result is a beer with a rich history and unique profile that offers a taste of the local terroir, making Lambic a celebrated style within the realm of craft and traditional brewing.