Available at: https://digitalcommons.calpoly.edu/theses/214
Date of Award
MS in Civil and Environmental Engineering
Civil and Environmental Engineering
Based on results of its Aquatic Species Program (1978-1996), which sought to develop algae-to-liquid fuel technology, the U.S. Department of Energy has suggested that algal wastewater treatment may be incorporated into biodiesel production schemes to reduce the operating costs of both processes. the purpose of the current research was to evaluate the triglycerides produced by wastewater-grown algae for their suitability as a fuel feedstock and to investigate the effectiveness of several solvent mixtures and extraction procedures at recovering lipids from fresh algae. The research involved two separate experiments. The first determined the quantity and quality of lipids produced over the lifetime of a batch culture of algae grown in a small outdoor high-rate pond. Transesterification of the algal triglycerides yielded mostly saturated and monounsaturated 16 and 18-carbon fatty acid methyl esters, together comprising approximately 8 to 30% of the biomass in the pond. The average triglyceride production rate during the grwoth phase of the culture was 0.97 grams per square meter of pond surface per day. The second experiment compared several industrially practicable extraction procedures to the Bligh and Dyer laboratory extraction method. The Bligh and Dyer laboratory extraction procedure provides excellent lipid recovery efficiency, but several factors limit its potential on an industrial scale. The Bligh and Dyer method requires a larger volume of solvents than other methods, uses the probable carcinogenic chemical chloroform, and involves a complex series of steps that are difficult to automate. A simple, low-energy extraction process using relatively non-toxic solvents was found to have an extraction efficiency comparable to that of the laboratory method.