Techno-Economic and Life Cycle Assessment of Hydrothermal Processing of Microalgae for Biofuels and Co-Product Generation
Date of Award
Doctor of Philosophy (PhD)
Civil & Environmental Engineering
Traditional processing methods of algae to biofuels require dewatering after harvesting of the algae before the lipids can be extracted. This is typically the most energy intensive and therefore the most expensive step. Old Dominion University (ODU) has successfully utilized a flash hydrolysis (a kind of hydrothermal) process where proteins are solubilized into the liquid phase of product and the remainder lipid-rich, low nitrogen product is separated into a solid phase. The solid phase (lipid-rich) is then an ideal candidate for biofuel feedstock and the liquid phase, or hydrolysate, can be used for coproducts such as a source of nutrients for new batches of algal cultivation or fertilizer production. The importance of this research lies within the energy conservation associated with the flash hydrolysis process, the quality of the co-products that are generated during the flash hydrolysis process, and the subsequent processing methods utilized to recover the nutrients not directly used for biofuel products. Processes which complement each other in the processing of microalgae to biofuel must be utilized for improving life cycle assessment (LCA) and technoeconomic analysis (TEA) results. These LCA and TEA data are critical for investors in both the public and private sectors. A valuable return on investment must be quantified in order for investors to move forward with advanced biofuels production. A combination of resources are utilized in this dissertation to quantify the LCA and TEA of the hydrothermal processes that are utilized in the ODU Biomass Research Laboratory (BRL) which include Argonne National Laboratory GREET, SuperPro Designer, Aspen Plus, and SimaPro’s Ecoinvent databases. This dissertation evaluates the novel processes researched in the BRL from the microscopic flash hydrolysis process level to a community level macroscopic evaluation. The clarity of how the flash hydrolysis compares with other hydrothermal processes is studied by conducting a LCA comparison. The flash hydrolysis process is then modeled utilizing two different microalgae species with varying cultivation and nutrient extraction properties. The alternate downstream processing methods for recovering preserved nutrients is then modeled for LCA and TEA results in order to quantify how coproduct generation offsets energy costs associated with algae biofuel processing. The final chapter of this dissertation utilizes the LCA and TEA results captured within the preceding assessments to develop a sustainable community model with algae cultivation and downstream processing at the focus of the sustainable community and an ultimate goal of zero net energy and zero waste system boundaries for the community.
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Bessette, Andrew P..
"Techno-Economic and Life Cycle Assessment of Hydrothermal Processing of Microalgae for Biofuels and Co-Product Generation"
(2018). Doctor of Philosophy (PhD), Dissertation, Civil & Environmental Engineering, Old Dominion University, DOI: 10.25777/rxmd-g747