Last year, the U.S. military used more than five billion gallons of petroleum-based fuels. Transporting the fuel to battle zones and remote military bases is costly and time consuming, and the fuel is a prime target of terrorists. So the U.S. Department of Defense is looking for cheaper, more secure, and easier options.
Two companies, Diversified Energy and Velocys, are working together on a portable system that converts coal, natural gas, and biomass into diesel and jet fuel. The military could use the system to convert waste created at military bases–food scraps, paper, wood–into a fuel for military jets and vehicles.
The system has two main parts: a gasifier and a fuel reactor. Diversified Energy, an energy company based in Gilbert, AZ, will make the gasifier that converts any carbon-containing material into a mix of carbon monoxide and hydrogen, known as synthesis gas, or syngas. The fuel synthesizer made by Velocys, based in Plain City, OH, will convert the syngas into a hydrocarbon liquid fuel.
Converting waste into fuel at defense bases is the answer to two problems that the military faces, says Eric Sattler, project engineer at the army’s Tank-Automotive Research, Development and Engineering Center, which is funding the new project. The transportation of fuel to bases accounts for 70 percent of military trucks and convoys that are on the road in Iraq and Afghanistan. At the same time, the military has to truck out waste from bases to dispose of it.
Portability is the key aspect of the waste-to-fuel system. Erik Kallio, power and energy technology team leader at the army’s research and engineering center, says that the system will have to be scalable to different sizes, making daily anywhere from about 2,100 to 21,000 gallons of fuel, while weighing between 150 and 1,500 tons, respectively. The system should also be able to make fuel from various feedstocks, including coal and natural gas.
Jeff Hassannia, vice president of business development at Diversified Energy, says that the new gasifier and reactor technologies should meet these requirements. The military should be able to move the system on a semitruck or an aircraft carrier, he says.
In conventional gasifiers, hot steam or air is mixed directly with the biomass. But in Diversified Energy’s gasifier, coal or biomass is introduced into a bath of molten iron and tin at a temperature of 1,300 °C to which steam has been added. Any carbon source immediately gasifies and produces carbon monoxide and hydrogen, says Hassannia. Using molten metal keeps the gasifier compact and produces syngas with significantly fewer impurities, which eliminates the cost of cleaning it.
Velocys’s reactor, which converts the syngas into liquid fuel, is also compact and efficient. It is made of tiny crisscrossing channels, each between 0.01 and 0.2 inches wide. The syngas flows through some of these channels, where it comes in contact with a cobalt-based catalyst and gets converted into long chains of hydrocarbons. Other channels in the reactor carry a coolant–typically water–to absorb the heat from the catalytic reaction.
The tiny channels increase the contact between the syngas and the catalyst, and they transfer heat quickly, speeding up the fuel production process by 10 times over conventional reactors. Velocys’s prototype reactor is about two feet long and one foot wide. Commercial synthetic fuel reactors are about five feet in diameter and 20 to 25 feet long.
So far, both Diversified Energy and Velocys have done lab demonstrations. They now plan to integrate the two components and analyze whether this will meet the army’s requirements. Then they will have to compete with other companies to develop and commercialize the system.