Thesis
Using anaerobic digestion to break down microalgae cell walls and enhance lipid extraction
Washington State University
Master of Science (MS), Washington State University
05/2016
Handle:
https://hdl.handle.net/2376/102416
Abstract
Microalgae cultivation and subsequent processing for production of lipids as a precursor for biofuels continue to be an active area of research. The existing lipid extraction technologies are subjected to limitations of potential environmental impact, high energy consumption, and high costs. The primary purpose of this study was to investigate a more sustainable yet efficient way to break down the microalgae cell wall, which is a necessary process for lipid extraction. Ideally, this method should have minimal environmental impact and waste residues. Anaerobic digestion, which is typically considered only for treatment of microalgae residue, was used for this application. Anaerobic digestion was designed here to perform multi-functions, including degrading the cell wall, releasing undigested lipid fraction as long-chain fatty acids (LCFA) to be collected and digesting the residue--all in a single unit operation. The microalgae cell wall degradation was accomplished through pH controlled biological hydrolysis. The results showed that sludge hydrolysis was significantly improved in an alkaline environment, the highest SCOD obtained was 12,273.33 mg/L at pH 11.0. The LCFA release was accomplished during the acidogenesis step under alkaline conditions when activities of acetogenic and methanogenic bacteria were extremely low or highly inhibited. Under the same pH conditions (pH=11.0), the maximum LCFAs concentration of 1.15 mg/ml was observed on the fourth day of treatment. Indigestible microalgae residues collected to produce methane yielded 407.5 ml of methane per gram of volatile solids processes. This novel and integrated approach provides a technical alternative for lipid extraction within an algal bio-refinery.
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Details
- Title
- Using anaerobic digestion to break down microalgae cell walls and enhance lipid extraction
- Creators
- Yaojing Qiu
- Contributors
- Shulin Chen (Chair)Pius M Ndegwa (Committee Member) - Washington State University, Biological Systems Engineering, Department ofJoseph H. Harrison (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Systems Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Number of pages
- 66
- Identifiers
- 99900525195801842
- Language
- English
- Resource Type
- Thesis