In 2017, in conjunction with the Micra Biodiagnostics department at IT Tallaght and with funding from Enterprise Ireland, Black Donkey’s brew crew initiated a project to harvest wild yeast strains from the Roscommon countryside. The project became known as “The Wild Yeast Chase”. The whole project from start to finish was documented through Facebook Live videos which you can rewatch for an interesting and entertaining binge. 

A Project, an Experiment and an Adventure!

The Black Donkey crew embarked on an experiment to try and capture a wild, native Irish yeast strain, with the aim of brewing a uniquely Irish beer, with an unparalleled provenance. The goal of this adventure was to isolate a unique strain of yeast, indigenous to the locality of the brewery. We hoped that this would become the base for new recipes, truly unique to Black Donkey Brewing.

Going Underground in Roscommon!

Located only 20 minutes from the brewery, Rathcroghan is an ancient heritage site extending over 6 square kilometres, encompassing national monuments, natural limestone caves, burial mounds and ring-forts. The ancient landscape is soaked in history, and was witness to the rise and fall of great tribes, chieftains and dynastic families. It was home to the great Iron Age Warrior, Queen Medb who ruled all of Connaught from Rathcroghan, and also the boy hero Cúchulainn. Additionally the area was also rumoured to have been the lair of the legendary goddess “Morrigan” and the origin of Samhain or Halloween.

Native Irish Yeast

Work started on Halloween 2017 when we gathered samples of the air, flora and substrate from in and around Oweynagat cave, also known as the “Hellsmouth of Ireland”. True to form, the cave yielded up some of its legendary magic. These samples were returned to IT Tallaght where they were isolated, purified and yeast strains identified. The resulting samples were then propagated, monitored, analysed and classified. Three successful strains returned home to Roscommon in early January 2018.

Morrigan Strain #1 yeast

Morrigan Strain 1 was the yeast eventually propagated for use, and named after the legendary warrior goddess who once inhabited the Oweynagat cave. It was harvested from a blackberry bush just above the cave’s tiny entrance. On March 8th 2018 the first pilot batch of beer was created. We called this new native Irish beer “Underworld”

Underworld – the first Irish Native Beers

The first production batch of Underworld was released in June 2018. The first beer from that batch was called Underworld Savage Ale. It was a light-bodied, dry and citrussy farmhouse ale with plenty of funky and earthy flavours. The Underworld series was expanded and rebranded for its full launch in 2021.

Underworld Savage outside Oweynagat Cave 2018 Wild Yeast Chase

Follow the Wild Yeast Chase

Follow our Facebook live video series which documented our journey to hell and back in pursuit of a unique yeast, which would give our brewing a true sense of place, and an unparalleled provenance. Such a unique project attracted a lot of national and international attention; you can read some of the local and international articles written about our journey and its results.

Wild Yeast chase Richard holding Underworld beer bottle outside Oweynagat Cave roscommon final

Enjoy the fruits of the Wild yeast Chase!

P.S. You can now enjoy the fruits of the Wild Yeast Chase, artfully presented in the Underworld series of three unique, native beers; Savage, Allta and Rua. For the feast of Samhain, we have put together a unique and limited edition Underworld gift packBlack Donkey Brewing came into existence 8 years ago and we have been brewing without boundaries ever since. Discover our beers in all good stockists or shop directly from our brewery shop or webshop

Handmade, real Irish Beer from Roscommon!



Black Donkey Brewing Ltd. Roscommon’s only Microbrewery. Brewing without boundaries. Specialising in bottle conditioned ales.

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