In a recent study conducted by researchers from Utah State University, it was found out that biodiesels from microalgae, yeast, and bacteria can effectively replace diesels from both petroleum and soybean.
Selecting representatives for microalgae, yeast, and bacteria – Chaetoceros gracilis, Cryptococcus curvatus, and Rhodococcus opacus, respectively, the research team compared their key physical properties and actual engine performance with those of petroleum- and soybean-based diesels.
Results showed that the three types of microbes have comparable physical properties to soybean-based biodiesel and are within ASTM D6571 specification.
Engine testing results showed that petroleum diesel generated the highest power output at 8.5 hp, followed by soybean biodiesel, yeast and microalgae, and bacteria, which have the least power output at 7.8 hp. The same trend resulted for their exhaust gas temperatures, while not much of a difference was found in terms of their torque output.
For one unit of power output, the biodiesels consumed more fuel than petroleum diesel. However, the CO2 emissions are lower for the biodiesels. On the other hand, the biodiesels produced higher NOx emissions than petroleum diesel, except for microalgae that produced significantly lower NOx gases than petroleum diesel.