Effects of thermal pre-treatment on anaerobic digestion of Nannochloropsis salina biomass for biogas production
Adams, Kameron J.
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Nannochloropsis salina is looked at as an exemplary species for anaerobic digestion because of its high biomass productivity and its high lipid content. Although considered a model species, cell wall degradation of N. salina is a limiting factor for efficient anaerobic digestion, but can be overcome with pre-treatment. The objective of this experiment was to test the effects of thermal pre-treatment by autoclaving at 121°C for Nannochloropsis salina as a feedstock for anaerobic digestion. The objective was to quantity the volume of biogas that would be produced for treated and non-treated feedstock for anaerobic digestion. Concentrations of total nitrogen and ammonia were analyzed in treated and non-treated effluent and feedstock. At the end of the 30 day residence time, non-pretreated biogas amounted to an average of 725.04 ml (.725 L) of biogas per day, and for pre-treated feedstock there was an average of 725.04 ml (.725 L) of biogas was produced per day. Gas production values were taken from when the system reached a steady state gas production. There were higher amounts of nutrients in the pre-treated feedstock and effluent indicating some form of cell disruption. The results for these tests would suggest that the treatment did not successfully increase biogas production because of very similar steady state volume averages. This would require further analysis of biogas composition for continuing studies. A suggestion would be to increase autoclave pre-treatment conditions to higher temperatures that would be high enough to biodegrade cell wall composition; thereby increasing biogas production.