Ireland’s Whiskey Boom Is Feeding a Black Fungus on Nearby Surfaces

Ireland’s expanding whiskey industry has an unusual byproduct: dark fungal growth on walls, roofs, road signs, trees and other surfaces near some maturation facilities. According to reporting published by Phys.org, the organism is Baudoinia, often called “whiskey fungus” or “whiskey black.” It can thrive where ethanol from aging whiskey enters the surrounding air. During maturation, alcohol and other volatile compounds pass through porous barrels in a process known in the industry as the “angels’ share.” More than 90% of whiskey-related emissions of non-methane volatile organic compounds are estimated to occur during maturation, according to a review commissioned by the Scottish government. Ethanol is the dominant component of those emissions. When the vapor mixes with moisture in the air, it can create conditions that encourage Baudoinia to grow. The fungus has been associated with spirit-aging facilities for more than a century. Similar growth has been documented around maturation warehouses in France, Scotland, Canada and the United States. In Ireland, its presence has attracted attention as whiskey exports continue to expand; exports were worth more than €930 million in 2025, Phys.org reported. It is not yet clear how far the fungus can travel from a facility or whether it commonly reaches residential properties. In 2022, Ireland’s Environmental Protection Agency investigated black discoloration reported near the Midleton distillery in County Cork. Baudoinia was found on a whiskey warehouse, but testing did not detect it on three nearby homes that were sampled. Researchers say visible growth may depend on several factors, including distance from the ethanol source, wind, moisture, and the characteristics of the surface. A recent review led by University College Cork also suggested that ethanol may help trigger fungal germination and provide carbon for growth. The fungus’s appearance should not by itself be taken as evidence of a health danger. The Scottish review found no demonstrated health effects from short- or long-term exposure to Baudoinia, while also noting significant gaps in the available evidence. A new EPA-funded project involving Dublin City University and the University of Toronto will examine ethanol emissions, the environmental distribution of Baudoinia, its biology and the way whiskey-maturation emissions are regulated in Ireland. Researchers plan to combine emissions estimates, environmental monitoring and laboratory work.