Date of Submission
5-2025
Document Type
Thesis
Degree Name
Master of Science in Chemical Engineering
Department
Chemistry and Chemical Engineering
Advisor
Kristine Horvat, Ph.D.
Committee Member
Nagasree Garapati, Ph.D.
Committee Member
Joseph Levert, Ph.D.
Keywords
Microalgae Dewatering, CO2 Gas Hydrate, Algal Oil extraction, Chlorella Algae Concentration, Biofuel Production, Thermodynamic Stability
LCSH
Microalgae—Biotechnology, Algal biofuels
Abstract
When microalgae are processed for producing biofuel, dewatering the algae is an important step, particularly when combined with extracting valuable byproducts like algal oil. Conventional methods like centrifugation and filtration can be harsh on the algae and usually need high-energy inputs. In this work, the new application of CO2 gas hydrates as an algae dewatering agent was investigated. A CO₂ hydrate, CO2-nH2O, where n (n>5.75), is a nonstoichiometric compound where water molecules with hydrogen bonds are structured in an ice-like fashion to form polyhedral cavities. CO₂ gas hydrates are crystalline because gas molecules are trapped in a lattice of water molecules. Water can be effectively removed from the algal biomass by trapping water molecules. The efficacy of this method in decreasing the water content of the algae was assessed. The Parr reactor's pressure and temperature, along with the Chlorella algae concentration, were important in the formation of CO2 gas hydrates. Six experiments with different pressures and Chlorella algae concentrations were performed, where CO2 gas was charged into a Parr reactor. The reactor system was then cooled to temperatures within the hydrate stability zone. The pressure and temperature of the Parr reactor were monitored over time, and the formation and dissociation datasets were analysed and compared with theoretical data from CSMHYD software. From the experimental results, it was inferred that high pressure with low concentration of the Chlorella algae was ideal for the CO2 gas hydrate production and thermodynamic stability. Since the dried algal yield was too low, the extraction of the algal oil for biofuel production was not successful under these relatively small experimental volumes. Overall, the outcome is a promising direction toward mass biofuel production systems and CO2 gas hydrate-based dewatering tools for the future production of biofuels and high-value byproducts through the application of algae.
Recommended Citation
Oak, Sumeet, "Dewatering of Chlorella Algae Using CO2 Gas Hydrate Formation for the Biofuel Production" (2025). Master's Theses. 257.
https://digitalcommons.newhaven.edu/masterstheses/257