By Robin J. Johnson, Ph.D.
The US Department of Defense's focus on renewable fuels represents a huge opportunity for companies in the biofuels sector. (In 2008, it was reported that the US military bought 130 million barrels of petroleum oil per year.) In Norfolk, Virginia, the US Navy has begun testing an experimental Riverine Command Boat, which will run on a fuel blend containing 50% algae-based renewable diesel fuel and 50% conventional Navy distillate fuel, NATO F-76. The renewable diesel is provided by algae producer, Solazyme, in partnership with Honeywell subsidiary, UOP.
Contrary to some reports, the algae biofuel used in the testing is not biodiesel, but a drop-in fuel made by hydroprocessing of plant oils. The hydroprocessing technology developed by UOP is similar to processes used in conventional oil refineries. By adjusting catalysts and reaction conditions, the process can produce mid-distillate fuels as well as jet fuels. In 2009, Air New Zealand, Continental Airlines, Japan Airlines and KLM Royal Dutch Airlines all successfully tested UOP's aviation biofuel, Bio-SPK (bio-synthetic paraffinic kerosene). In April of this year, the Navy tested renewable jet fuel in an F/A-18 Super Hornet aircraft.
Hydroprocessed biofuel has several advantages over conventional biodiesel fuel. Biodiesel is made up of esters of fatty acids and a small alcohol, most often methanol. It is a suitable replacement for diesel fuel, but does have a tendency to gel at cold temperatures and can also undergo oxidation. The extent of the problems caused by these drawbacks is determined to a large extent by the type of oil used in the processing. Oils with long, saturated fatty acids are more susceptible to gelling, but fairly resistant to oxidation. The opposite is true of oils containing shorter, unsaturated fatty acids. The molecules that make up hydroprocessed biofuels are similar to those found in petroleum-based fuels, making the biofuels more fully compatible with existing infrastructure. A main drawback with hydroprocessed fuels is that it may not be easy or cost-effective to generate the hydrogen required from renewable sources.
Secretary of the Navy Ray Mabus has ordered the US Navy sea service to use alternative energy sources (e.g., biofuels and nuclear power) for half of its total energy consumption by 2020. The fact that hydroprocessed biofuels have already been successfully tested in military and civilian applications bodes well for this technology. Having the DOD as a customer can’t hurt the economics.
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