Anaerobic Fermentation Ripe cherry deliveries from Chelbiesa Village are first sorted by hand. The best cherries are then placed into Grain Pro bags with an added mixture of brewed yeast. The bags are sealed and as the fermentation of the coffee and yeast begins it produces CO2, creating an anaerobic environment in the bag. After 72 hours of fermentation, the cherries are removed from the bag and moved to dry on raised beds for 2–3 weeks until they reach their target humidity.