Algae have tapped into as a biofuel source before but never as the starting point for jet fuel. Now a team led by Gregory O'Neil and Christopher Reddy have managed to not just produce biodiesel but also derive jet fuel from the process, creating two biofuels from algae.
Published in the journal Energy & Fuels, their work involved exploring an unusual class of chemical compounds in the algae Isochrysis. The researchers focused on Isochrysis specifically because it was easy to source in large batches (manufacturers produce a lot of it for use as fish food) and it was one of a few algal species that are capable of producing fats known as alkenones.
Algae, in general, is a good biofuel source because it contains fatty acids that can be converted into FAMEs, or fatty acid methyl esters, molecules found in biodiesel. The fats particularly found in Isochrysis contain long carbon chains with 37 to 39 atoms which O'Neil, Reddy and colleagues believed had the potential to be a fuel source.
Biofuel prospectors recognize the potential algae has as a fuel source but have shunned Isochrysis because of its dark, sludgy appearance at room temperature. However, this dark, sludgy appearance is the work of the alkenones in the algae, which is what researchers were going after in the first place, so looking less-than-ideal was not a concern for them.
Additionally, biofuel prospectors did not know that alkenones have the ability to change structure as a response to changing water temperature. Oceanographers, some of which were on the research team, knew this and thus believed in the potential alkenones had.
To create the biodiesel, O'Neil and Reddy developed a method for separating alkenones and FAMEs. The process they came up with added steps to the process of making biodiesel but it resulted in biodiesel that's superior in quality.
The long carbon chains alkenones had, however, were not ideal for jet fuel. Researchers turned to olefin metathesis to break the chains into smaller pieces with just 8 to 13 atoms each, small enough to be used in jet fuel.
Aside from producing jet fuel and biodiesel in larger quantities, researchers are also exploring other products that could be derived from the algae Isochrysis.
The study received funding support from the Woods Hole Oceanographic Institution, the Massachusetts Clean Energy Center and the National Science Foundation. Robert Swarthout, Robert Nelson, Catherine Carmichael, Garrett Gilbert, Noah Burlow, John Williams and Aaron Culler also contributed to the research.
