Isobutanol to the Rescue

Since its founding in 1790 as the U.S. Revenue Cutter Service, the U.S. Coast Guard has had a history of implementing new technology within its fleet. During the U.S. Civil War, for example, the USRC Naugatuck boasted twin-screw engines, ironclad armor and semisubmersible technology that allowed it to increase or decrease the ship’s draft in shallow waters. Continuing its pursuit of maritime innovation and reinforcing its motto of Semper Paratus (Always Ready), the USCG is conducting a year-long engine test using renewable, isobutanol-blended gasoline through a Cooperative Research and Development Agreement with Gevo Inc., Honda Motor Co. Ltd. and Mercury Marine.

With a fleet of more than 2,000 cutter ships, boats and aircraft that conducted 19,790 search and rescues in 2012, cost-effective advanced biofuels that meet the USCG’s standards will help the organization break its reliance on foreign fuel sources and provide a stable fuel source in the event a conflict disrupts fuel supply lines.

Producing the Fuel

In 2011, the USCG began an alternative fuel study, motivated by the government’s desire to minimize its carbon footprint, says Michael Coleman, project manager for the U.S. Coast Guard Research and Development Center. From that initial study, the USCG researched different alternative fuels for their affordability, availability, safety and potential carbon footprint reduction. The USCG selected four fuels: natural gas, ethanol blends, biobutanol and biomass liquid fuels. “Out of those four fuels, we did a desktop evaluation including many technical factors including maturity, performance, physical safety and logistics,” Coleman says. “Out of those, we decided to proceed with biobutanol as our test fuel.” 

For the engine tests, the USCG is sourcing the isobutanol-blended fuel from Gevo’s plant in Luverne, Minn. The USCG selected a blend of 16.1 percent isobutanol and gasoline because of its potential benefits in an aquatic environment. “The Coast Guard, along with many other folks in the marine industry, is very interested in next-generation biofuels instead of ethanol-blended gasoline,” says Brett Lund, chief licensing officer for Gevo. He adds ethanol-blended gasoline is currently not compatible with most boat engines and its solubility with water make isobutanol a more attractive option.

Gevo’s Luverne facility is a retrofitted ethanol plant that produces isobutanol using Gevo’s Integrated Fermentation Technology. Gevo is producing 8,700 gallons of blended isobutanol fuel at the facility for the Coast Guard tests.

Producing the fuel presented some challenges that Gevo had to overcome, says Lund.  Yeast naturally wants to produce ethanol, and small amounts of isobutanol.  “We’ve spent quite a bit of time, five years or so, using metabolic engineering to develop a yeast that makes, almost exclusively, isobutanol,” he says. He notes isobutanol is toxic to the yeast and causes it to perish, therefore Gevo also had to develop a tolerant yeast strain. As the isobutanol is produced in the broth, Gevo extracts the isobutanol vapor under vacuum and condenses it into a liquid. “That really allows us to get the isobutanol out of the process without having to use conventional distillation to remove the water,” Lund explains.

Setting Sail

After the initial alternative fuel study, the second phase of the isobutanol tests under the CRADA occurred over a three-month period in early 2013 using Honda outboard engines and craft, since Honda is one the major engine manufacturers for the USCG, Coleman says.  In addition to material and benchmark testing, Honda also put the isobutanol blend through an endurance test prior to giving the USCG the approval of trying the fuel in its own boats, he explains. During Honda’s test, the engines operate at full throttle for eight hours a day over several months and then are taken apart and inspected.

The next round of fuel tests are in progress at the U.S. Coast Guard Training Center in Yorktown, Va. “The training center is basically an area where Coast Guard members can learn how to operate the different boat platforms, be it anywhere from standard boat handling procedures to the mechanics of those craft,” says Lt. Kevin Sorrell. The center is a convenient location for testing due to its availability compared to other operational units, he adds.

At the Yorktown training center, the fuel is being tested on a 38-foot special-purpose craft using Mercury outboard engines as well as a 25-foot response boat (RBS) that uses Honda outboard engines.  “Both crafts are operationally used in the Coast Guard,” says Sorrell. “RBSes are basically stationed all throughout the United States. The special purpose craft is more of a law enforcement craft, specifically used down in the southern U.S., like the Gulf of Mexico and Florida area.”

“What we hope to accomplish with this project is to get the information that’ll give the Coast Guard decision makers the ability to make an informed decision on whether to proceed with butanol as an alternative fuel,” says Coleman.

If the fuel tests turn out for the better, a positive testimonial from the USCG could be quite valuable for the advanced biofuel and boating industry. “This is really the option they are most excited about for their fleet and their industry. The fact that it’s all home-grown and the isobutanol is 100 percent produced in the U.S. is also beneficial,” says Lund. “They, as well as other branches of the military, like solutions like that because you avoid some of the risk of being cut-off from fuel supply.”

“The nice part from our perspective is, if it’s good enough for the U.S. Coast Guard, it’s pretty much good enough for any marine application out there,” Lund adds. “Nobody runs their boats like these guys do.”

Author: Chris Hanson
Staff Writer, Biomass Magazine
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