Characterization and Microwave Assisted Pyrolysis of Oklahoma Native Microalgae Strains for Bio-oil Production
MetadataShow full item record
Microalgae have received significant interest as a potential feedstock for the production of biofuel and other bioproducts. The main advantages of microalgae over the existing energy crops include the higher biomass production rate and not competing for resources needed for conventional agriculture. Selection of the appropriate algae species is crucial for the success of microalgae production systems. Pyrolysis is a thermochemical conversion technique in which biomass is thermally decomposed into bio-oil and other products. In this study, seven algae strains isolated from the Great Salt Plains of Oklahoma, UTEX SP20, SP22, SP38, SP46, SP47, SP48, and SP50, were cultivated under controlled growth conditions. The growth parameters, chemical composition, and fatty acid profile of each strain were determined. Biomass thermal degradation behavior of each strain was examined by thermogravimetric analysis. Kinetic parameters were determined by using an iso-conversional approach. Algal biomass was used as feedstock for bio-oil production via microwave assisted pyrolysis, and the effects of final temperature on the product yields and bio-oil composition were evaluated. Among the seven strains, SP46 produced the highest final biomass concentration (1.32 g/L), the highest biomass productivity (55.9 mg L-1day-1) and the lowest lipid content (9.2% based on ash free and dry weight). Due to these properties, SP46 was selected out of the seven strains for microwave assisted pyrolysis. Thermogravimetric analysis revealed that pyrolysis of algae biomass took place in three stages, with major weight loss occurring at the second stage from around 150 oC to 400 oC. The apparent activation energy was a function of degrees of conversion. Biomass of SP38 had the lowest average apparent activation energy, 102.8 kJ/mol, indicating that biomass of SP38 requires the least energy for pyrolysis among the seven strains. During the microwave assisted pyrolysis of SP46 biomass, the bio-oil yield increased from 4.6% to 22.5% with the increasing final temperature from 450 oC to 750 oC. The major compounds in the bio-oil included acids, aliphatic hydrocarbons, aromatic hydrocarbons, phenols, organic nitrogen compounds.
- OSU Theses