Proceedings

The poor biodegradability of activated sludge cell walls is well known and it has been suggested that the rigid, double layered
yeast cells will be even more recalcitrant. The worldwide yeast processing business is large and may increase with the
interest in natural products and nutrients. This paper describes the Anaerobic Digestion of concentrated yeast cell walls (COD
100 g/l and VS 60g/l). Laboratory scale (23 litre) digesters were used to research and design the process achieving average
loading rates of 2.5 kgVS/m³.d with gas yields of 2 m³/KgVS destroyed from a 70% destruction of volatile solids.
BMP trials at 500ml scale, demonstrated that pre-treatment using ultrasonics further enhanced this yield by 28%. It was
concluded that further research on the structural differences of other types of recalcitrant biomass would be useful. BMPs
were an effective screening technique to compare alternative pre-treatment.

KEY WORDS
Anaerobic Digestion, Yeast Cells, Ultrasonic pre-treatment.