Chemical and physical properties of algal methyl ester biodiesel containing varying levels of methyl eicosapentaenoate and methyl docosahexaenoate

Published Date
Algal Research
May 2012, Vol.1(1):57–69, doi:10.1016/j.algal.2012.02.001

• Author 

• Harrison B. Bucy
• Marc E. Baumgardner
• Anthony J. Marchese ^,

• Colorado State University, Fort Collins, CO 80523, United States

Received 30 November 2011. Revised 1 February 2012. Accepted 7 February 2012. Available online 5 March 2012. 

Abstract

Microalgae are currently receiving strong consideration as an advanced biofuel feedstock because of their theoretically high yield (gal/acre/year) in comparison to terrestrial vegetable oil feedstocks. Microalgal lipids can be readily converted into a variety of biofuels including fatty acid methyl esters (i.e. biodiesel) via transesterification or alkanes via hydroprocessing. In contrast to paraffinic fuels whose properties can be tailored for a specific application, the properties of algal methyl ester biodiesel are directly related to the fatty acid composition of the algal lipids. Several microalgae species that are suitable for large scale cultivation such as those in the genus Nannochloropsis produce lipids that contain long chain-polyunsaturated fatty acids (LC-PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These constituents have high value as co-products but are problematic in terms of biodiesel properties such as ignition quality and oxidative stability. The objective of this study was to examine the effect of varying levels of EPA and DHA on algal methyl ester fuel properties. Oxidative stability, Cetane Number, density, viscosity, bulk modulus, cloud point and cold filter plugging point were measured for algal methyl esters produced from various microalgae feedstocks as well as model algal methyl ester compounds formulated to match the fatty acid composition of Nannochloropsis sp., Nannochloropsis oculata and Isochrysis galbana subjected to varying levels of removal of EPA and DHA. The results suggest that removal of 50 to 80% of the LC-PUFA from Nannochloropsis-based methyl esters would be sufficient for meeting existing specifications for oxidative stability. However, higher levels of LC-PUFA removal from Nannochloropsis-based methyl esters would be required to produce fuels with acceptable Cetane Number. The removal of EPA and DHA was shown to have a detrimental effect on cold flow properties since the algal methyl esters are also high in fully saturated fatty acid content.

Keywords

Algal biofuels

Biodiesel

Oxidative stability

Ignition quality

Cold flow properties

Fatty acid composition

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  Corresponding author at: Department of Mechanical Engineering, Colorado State University, 1374 Campus Delivery, Fort Collins, CO 80523-1374, United States. Tel.: + 1 970 491 2328; fax: + 1 970 491 3827.

Copyright © 2012 Elsevier B.V. All rights reserved.

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