The researchers studied how mixing coffee waste with other organic wastes affects biogas production. They tested different mixtures of coffee waste, cow manure, food waste, and anaerobic sludge in anaerobic conditions. Mixing coffee waste with anaerobic sludge increased biogas production by 12%. However, mixing coffee waste with cow manure or food waste decreased biogas production. When cow manure was mixed with coffee waste, biogas production decreased by 43.8%-85.1%, depending on the coffee waste content. Mixing coffee waste with food waste only resulted in biogas production from the food waste.