A technical evaluation of biodiesel from vegetable oils vs. algae. Will algae-derived biodiesel perform?

Abstract

Biodiesel, one of the most prominent renewable alternative fuels, can be derived from a variety of sources including vegetable oils, animal fats and used cooking oils, as well as alternative sources such as algae. While issues such as land-use change, foodvs.fuel, feedstock availability, and production potential have influenced the search for the “best” feedstocks, an issue that will ultimately determine the usability of any biodiesel fuel is that of fuel properties. Issues such as cold flow and oxidative stability have been problematic for biodiesel. The fatty acid profile of a biodiesel fuel is largely identical to that of the feedstock and significantly influences these properties. This article compares biodiesel derived from vegetable oils and biodiesel obtained from algae in light of fuel properties. While the properties of biodiesel fuels derived from vegetable oils are well-known, the properties of biodiesel obtained from algal oils have usually not been reported. The fatty acid profiles of many algal oils possess high amounts of saturated and polyunsaturated fatty acids. Thus, biodiesel fuels derived from algae in many cases likely possess poor fuel properties, i.e., both poor cold flow and low oxidative stability simultaneously. This observation shows that production potential alone does not suffice to judge the suitability of a feedstock for biodiesel use. This article also summarizes how the fuel properties of biodiesel can be improved through modification of the fatty ester content. Algal oils for biodiesel production are probably best produced under tightly controlled conditions since the fatty acid profile of algal oils is very susceptible to changes in these conditions. Algal oils likely yielding biodiesel with the least problematic properties as determined by reported fatty acid profiles are discussed.