Creating gasoline and biodiesel from readily available microbial organisms may sound too good to be true, but that is exactly what researchers at the Hawai‘i Natural Energy Institute at the University of Hawai‘i at Mānoa are doing. A new one-pot process is described in a recent publication by HNEI Postdoctoral Fellow Shimin Kang and Researcher Jian Yu.
“As we refine this process, we will be able to simplify and bring down the cost of converting renewable feedstock to commercially viable transportation fuel,” said researcher Kang.
Biomass to biofuel
There are several different types of feedstock—defined as any renewable, biological material (biomass)—that can be used directly as a fuel or converted to another form of fuel or energy product. Common examples of biomass feedstocks include corn starch, sugarcane juice and purpose-grown grass crops that can be used to derive fuels like ethanol, butanol, biodiesel and other hydrocarbon fuels.
For a fuel to be considered good enough to use in modern high performance automobiles, it needs to have a high antiknock quality (octane number) and low oxygen. Since biomass generally has high oxygen content, it can be a challenge to create a high quality fuel without using multiple complex steps under high pressures and temperatures that can result in high costs of equipment and operation. Researchers are addressing this challenge by testing alternative feedstocks and new processing technology.
Bacterial biomass and a solid catalyst
Like starch and oil accumulated in plants, polyhydroxybutyrate (PHB) is an energy storage material accumulated from renewable feedstock in many microbial species. Following up on studies showing that PHB could be reformed into oil in liquid phosphoric acid solutions, Kang and Yu tested the process using a solid phosphoric acid as a catalyst. They were able to produce high quality bio-oils, a light gasoline-grade biofuel and a heavy biodiesel-grade biofuel, in a simple one-pot reaction.
“By using a solid catalyst we were able to increase the aromatics content, thereby raising the octane number, while reducing the water content in the resulting commercial grade oils,” said Kang.
With this new, more efficient, method researchers were able to achieve results with reaction temperatures low in comparison to catalytic conversion of conventional biomass. This may help bring down the cost of conversion to biofuel. With future work building on these results, they hope to develop a standard method to create a consistent fuel.