Conference article

Due to high growth rates microalgae provide an enormous potential as a source for biomass besides conventional energy crops. The algal biomass can be used for bioenergy production. Anaerobic digestion to biogas is one of the most energy-efficient and environmentally beneficial technologies for alternative energy carrier production. The resistance of the algal cell wall is generally a limiting factor for cell digestibility. In the present work different cell disruption techniques (microwave heating; heating for 8 hours at 100°C; freezing over night at -15°C; French press; ultrasonic) on algal biomass of Nannochloropis salina were carried out. The disrupted material was digested to biogas in batch experiments according to VDI 4630. The results indicate that hydrolysis of algal cells is the rate-limiting step in anaerobic digestion of algal biomass. Cell disruption by heating; microwave and French press show a considerable increase in specific biogas production and degradation rate. Compared to the untreated sample the specific biogas production was increased for the heating approach by 58 %; for the microwave by 40 % and for the French press by 33 %.

Anaerobic digestion; Microalgae; Cell disruption; Specific biogas production; Pretreatment