Influence of Different Cell Disruption Techniques on Mono Digestion of Algal Biomass

Abstract

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 %.

Acutodesmus obliquus as a benchmark strain for evaluating methane production from microalgae: Influence of different storage and pretreatment methods on biogas yield

“…This result is contrary to our results, however, Schwede [20] used a different taxon not closely related to Acutodesmus (Nannochloropsis salina from the kingdom Chromista). Moreover, lower energies were used for ultrasonication by Schwede [20].…”

“…biomass compared to unfrozen control biomass. In contrast, Schwede [20] observed a negative effect on biogas yield of frozen Nannochloropsis salina biomass (233 Nm 3 t − 1 VS, − 33%) compared to live cells.…”

“…The larger effect of ultrasonication in our study was probably due to the application of a sonotrode with a flow cell (10 mL volume), which results in a shorter distance between the sample and the sonotrode. Schwede [20] mentioned that ultrasonication yielded a lower CH 4 yield, i.e., 274 Nm 3 t −1 VS (−21% compared to the control). This result is contrary to our results, however, Schwede [20] used a different taxon not closely related to Acutodesmus (Nannochloropsis salina from the kingdom Chromista).…”

“…Schwede [20] mentioned that ultrasonication yielded a lower CH 4 yield, i.e., 274 Nm 3 t −1 VS (−21% compared to the control). This result is contrary to our results, however, Schwede [20] used a different taxon not closely related to Acutodesmus (Nannochloropsis salina from the kingdom Chromista). Moreover, lower energies were used for ultrasonication by Schwede [20].…”

“…Thus, several studies have focused on disrupting the microalgal cell wall using various pretreatment techniques to enhance biomass biodegradability. These techniques included: thermal; enzymatic; biological; and mechanical processes [12][13][14][15]19,20].…”