(38f) Bio-Crude Quality and Composition from Algal Solids Cultivated in Varying Media, Growth Stage, and Solids Loading
Conventional HTL reactions at 350°C for 60 minutes were performed on various WW and raceway-cultivated algal solids. To simulate seasonal and regional differences of WW, algae were grown in two separate raceway ponds: one raceway that had N-limited media and the other P-limited. Algal solids were then harvested at different growth stages thus altering their biomolecular content and ultimately varying the biocrude composition. To regulate inorganic content of the algal solids, the algae were harvested via auto-induced flocculation that occurred from a manual increase in media pH. At each growth stage the total Ca:P molar ratio of the algal solids were manipulated to range between 1 and 3 with the addition of lime (Ca(OH)2), a common chemical used to balance the alkalinity and pH in WW treatment.
GC-MS results displayed dramatic change in oil composition dependent upon growth media, growth stage, and solids formed. Elemental CHN/O analysis indicated little change in N/C or O/C ratio between growth stages and media. However, the H/C ratio did change with the HTL solids produced from the reaction. Thus, further characterization of HTL solids were measured for their catalytic potential. In addition, fundamental reactions of model inorganic and algal compounds were also performed to better understand the mechanism of solid synthesis and biocrude upgrading.