Date of Submission

5-2020

Document Type

Thesis

Degree Name

Master of Science in Environmental Engineering

Department

Civil and Environmental Engineering

Advisor

Dr. Kristine Horvat

Committee Member

Dr. Emese Hadnagy

Committee Member

Dr. Eddie Luzik

Keywords

Carbon dioxide clathrate hydrate, Renewable energy alternatives

MeSH

Chlorella, Carbon dioxide, Biofuels

LCSH

Dewatering, Chlorella, Carbon dioxide, Biomass energy, Algae, Algal biofuels

Abstract

Renewable energy alternatives are currently of interest to meet ever-growing energy demands due to fossil fuel depletion and climate change. Biofuels, an alternative source, can be made from a range of organic matter. One option is algae, which can be grown without impacting food production and in a variety of conditions, however, the feasibility of converting algae into biofuel is of concern. Dewatering algae is a critical step in the process to make oil extraction more efficient. This study utilizes carbon dioxide clathrate hydrates as a novel process to dewater water saturated algae solutions. Clathrate hydrates are crystalline solids formed from water molecules that contain trapped gas molecules. Carbon dioxide is specifically trapped in Structure I hydrates that are composed of a 512 62 structure. A stainless-steel reactor was used to perform proof-of concept experiments using Chlorella sp. Experiments were performed with an initial pressure of 450 psig in a refrigerated circulator cooled to 2°C for three or more days with occasional agitation to encourage carbon dioxide hydrate formation. After performing several experiments, it was found that between 0.2 to 14.7 wt% of free water was converted into clathrate hydrates. Overall, the results show potential for the use of clathrate hydrates to dewater a water-saturated algae solution.

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