(619x) Biofuel Production Via Thermochemical Conversion of Algae and Optimizing Coproduct Utilization

Hydrothermal liquefaction (HTL) is a method for thermochemical conversion of wet algae that can produce energy dense biocrude oil as well as gaseous, aqueous and solid by products. In this study, three different algal species such as Galdieria, Kirchneriella and Micractenium were used as feedstock for the biofuel production. Process parameters like reaction temperature, time and solids loading were optimized to achieve maximum biocrude oil yield. A bench top 250 mL batch reactor was used for the HTL experiments and dichloromethane was used as a solvent for extraction. The maximum biocrude oil yield of 45.5% was obtained for Kirchneriella species at reaction conditions of 300 C, 90 bar, 30 min and 10% solids loading. Since the maximum biocrude oil yield achieved was less than 50% and to make this process economically viable, other co-products need to be utilized which adds value to the algal biorefinery. The aqueous phase will be rich in carbohydrates and soluble proteins and can be recycled to the cultivation facility. This nutrient rich aqueous phase upon required dilution was successfully used to cultivate algae. The biochar produced during the hydrothermal liquefaction has significant amount of phosphorous and nitrogen. These components were extracted as phosphates and ammoniacal nitrogen and were used as macronutrient supplement to grow algae. The growth experiments were investigated using a tissue Culture Roller drum apparatus with 16 mm borosilicate glass tube photo reactor and confirmed using a Microplate Assay at 40⁰C and 2-3 % COâ?? in an incubator. The remaining biochar was dried and used to produce porous carbon. Various analytical instruments such as gas chromatography mass spectrometry (GC-MS), CHNS/O analyzer, spectrophotometer, semi micro calorimeter and inductively coupled plasma optical emission spectrometry (ICP-OES) were used to analyze algal biomass and different products. In conclusion, HTL along with coproduct development has the potential to make algal biofuels sustainable.