Green Car Congress reports that biodiesel derived from microalgae, yeast, and bacteria can effectively outperform both petroleum diesel and biodiesel produced from plant oils, according to the findings of a new study by a team from Utah State University.

The researchers, who reported their results in a paper published in the ACS journal Energy & Fuels, examined the properties, engine performance, and emissions for biodiesel produced from the microalgae Chaetoceros gracilis; the yeast Cryptococcus curvatus; and the bacterium Rhodococcus opacus, all compared with commercial soybean biodiesel.

From the study: While biodiesel derived from plant seed oils has advantages as a replacement for petroleum diesel, there is strong interest in the potential for biodiesel produced from microbial derived oils because of potential use of contaminated water, the diversity of oils that can be produced, use of marginal lands, and potential for higher oil yields per acre. Three different groups of microbes are known to produce high neutral oils including select microalgae, bacteria, and yeast.

Plant-based oils, commonly used to produce biodiesel (e.g., soybean, canola, and sunflower) are similar to one another in terms of fatty acid composition, containing primarily C16 and C18 fatty acids with varying degrees of unsaturation. Microbial oils, however, can differ substantially and may contain uncommon fatty acids that differ in both chain length and structure.

This study demonstrates that microbial-derived biodiesel shows comparable properties in the parameters tested to soybean biodiesel. Future wide scale use of microbial oils as a source for biodiesel will require advances in large-scale cultivation, dewatering, and oil extraction.   —Whalen et al.

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