Inexpensive Jet Fuel from Microalgal Lipids
Probably our most pressing energy need is to develop domestic, renewable substitutes for transportation fuel. Ethanol made from starch or sugar such as corn grain already displaces gasoline and making it from cellulosic biomass will allow much greater displacement. Biodiesel made from oil crops such as soybeans can displace some of our diesel use.
Unfortunately, neither of these biofuels can help supply jet fuel, for which energy density and low-temperature fuel properties are critical. Ethanol is not dense enough having only about half the energy per volume of jet fuel.
Biodiesel has about 80% the energy density of kerosene, but can solidify at the low temperatures of high altitude flight. In addition, the quantity of biodiesel that could be produced from oilseed crops is quite limited.
The solution will come from a combination of hydroprocessing—a technology already used by petroleum refineries—and microscopic algae.
With various hydroprocessing technologies used by refineries to catalytically remove impurities or reduce molecular weight, the algal oils could be made into a kerosene-like fuel very similar to petroleum-derived commercial and military jet fuels or into a fuel designed for multi-purpose military use.
Many microalgae naturally store energy as oil when the lack of nutrients makes them unable to use the energy for normal growth. They also use the lipids to regulate their buoyancy. By manipulating nutrients and other growth conditions and by selecting and genetically engineering strains to increase this oil production, researchers are able to attain quite high lipid production levels.
As it happens, many microalgae grow best in saline water, and like any plants, they require sunlight and carbon dioxide.
The ability of microalgal cultures to utilize high volumes of carbon dioxide is so great that development of technology was motivated by the idea that greenhouse gas emissions could be reduced by passing flue gas from power plants, ethanol plants, oil and gas drilling operations, or other industrial sources through the cultures.
EBT is seeking to extend its microalgal oil research in partnership with oil refiners, with a particular view towards jet fuel production.
Military jet fuel carries a very high added cost and logistic difficulty of transport around the world. But there is considerable refining capacity strategically located around the world that could be used for hydroprocessing microalgal oil to jet fuel, with both offshore and onshore locations highly suitable for microalgae growth nearby.
Genetic engineering and screening technologies have advanced dramatically over the past decade.
Top research priorities include the following:
• Applying current strain selection, screening, and genetic engineering technology to increase lipid yields.
• Genetically manipulating the mechanism by which microalgae switch back and forth between normal growth and lipid production to maintain high rates for both.
• Optimizing the lipids produced for hydroprocessing into jet fuels or multi-purpose military fuels.
• Working with oil refiners to tailor hydroprocessing to use for converting microalgal oil to premium diesel or jet fuel.
EBT holds close interest with the Government of India DRDO Enhanced BioFuel Development Program.