A common algae commercially grown to make fish food holds promise as a source for both biodiesel and jet fuel, according to a new study published in the journal Energy & Fuels.

 

The researchers exploited an unusual and untapped class of chemical compounds in the algae to synthesize two different fuel products, in parallel, from a single algae.

 

Algae contain fatty acids that can be converted into fatty acid methyl esters, or FAMEs, the molecules in biodiesel. For their study, he researchers targeted a specific algal species called Isochrysis for two reasons: First, because growers have already demonstrated they can produce it in large batches to make fish food. Second, because it is among only a handful of algal species around the globe that produce fats called alkenones. These compounds are composed of long chains with 37 to 39 carbon atoms, which the researchers believed held potential as a fuel source.

 

Biofuel prospectors may have dismissed Isochrysis because its oil is a dark, sludgy solid at room temperature, rather than a clear liquid that looks like cooking oil. The sludge is a result of the alkenones in Isochrysis -- precisely what makes it a unique source of two distinct fuels.

 

Alkenones are well known to oceanographers because they have a unique ability to change their structure in response to water temperature, providing oceanographers with a biomarker to extrapolate past sea surface temperatures. But biofuel prospectors were largely unaware of alkenones.

 

The researchers began first by making biodiesel from the FAMEs in Isochrysis. Then they had to devise a method to separate the FAMEs and alkenones in order to achieve a free-flowing fuel. The method added steps to the overall biodiesel process, but it supplied a superior quality biodiesel, as well as “an alkenone-rich . . . fraction as a potential secondary product stream,” the authors write.