Breakthrough signals future low-cost fuel

MU physics professor Peter Pfeifer has been buying ground corncob by the pound as part of a research project that could put a natural-gas tank in many American cars in the next five years.

Pfeifer and his team heat the ground cobs at high temperatures in an oxygen-free atmosphere to reduce them to carbon, which is then pressed into round one-inch thick briquettes.

“It’s almost like charcoal that you put on your Fourth of July barbecue,” Pfeifer said. “Some people call them the Missouri hockey pucks.”

Then 216 carbon briquettes are placed into aluminum tubes. To the untrained eye, it seems they are taking up space but in fact, the carbon provides greater storage capacity for natural gas than an empty tank.

Natural gas is cheaper and cleaner-burning than gasoline. The equivalent in natural gas of one gallon of unleaded gasoline costs $1.40 — or the price of about a half gallon of gas. Burning natural gas produces fewer greenhouse gas emissions, and it produces virtually no exhaust. Natural gas is also easier to procure: 85 percent of the current U.S. consumption is produced domestically, according to the U.S. Department of Energy, and most of the rest comes from Canada.

“If it’s such a winning proposition, why aren’t you and I using such cars?” Pfeifer said.

The answer is that while automobile engines can burn natural gas without modification, doing so would require a different kind of fuel tank. Storing natural gas requires heavy steel high-pressure cylinders that are expensive and impractical for use in automobiles.

“You have to give up your trunk space or passenger space,” Pfeifer said.

Only six stations sell natural gas in Missouri, and four of them only sell to local governments who use natural gas vehicles, or NGVs, for public transportation and other government functions. Gas stations resist offering natural gas because of the high cost of storing and distributing it and because there are very few NGVs on the market today.

Kansas City has a central fleet of 218 NGVs. Next month, a team from the Midwest Research Institute led by Phil Buckley, who works with Pfeifer, will mount a prototype low-pressure tank on a pickup truck owned by the city. If the experiment works, Pfeifer and his team will have overcome the biggest obstacle to a wider use of NGVs. They could also help convince the automotive industry to begin building cars and trucks that burn natural gas.

“If we get an investor interested in this technology, it could be revolutionary,” said Sam Swearngin, fleet superintendent in Kansas City.

Pfeifer’s coworkers in MU’s department of physics jokingly call him a “fractalist.” A floor-to-ceiling bookshelf in his office is dedicated to the topic of fractals, his life’s work. Fractals are objects in which a pattern is constantly repeated so that no matter the scale, the object always looks the same. Think cauliflower: A head of the vegetable looks like one of the flowers, which is composed of smaller flowers, and so on.

“As you zoom in, the substructure looks like the whole,” Pfeifer said.

Cumulus clouds and human lungs are fractals. So are the pores inside the carbon that is produced by charring the ground corncobs.

These microscopic cavities in the carbon, “nanopores,” hold the natural gas — 95 percent of which is methane.

“Those pores are almost like a sponge, they suck up the methane,” Pfeifer said. “In this carbon, the methane, at a much lower pressure, is held at almost the same density as it would be in big cylinder tanks.”

Because the pressure is low, 500 pounds per square inch instead of 3,600, the tank can be made flat and rectangular, allowing it to be attached to a car like a regular gasoline tank. Until Pfeifer’s work, that was considered impossible for a natural gas tank because a rectangular shape is less resistant to high pressure.

“At high pressure, this would blow up in your face,” Pfeifer said.

The carbon system could also be used to capture the methane that emanates from landfills and transport it to central processing facilities, thus transforming a pollutant — methane is a greenhouse gas four times more potent than carbon dioxide — into a renewable energy.

If it becomes a reality, Pfeifer’s tank could be another energy-related benefit for the region. Corn farmers already stand to gain from the increasing use of ethanol, and one added advantage of Pfeifer’s tank is that it relies on a waste product that is cheap and abundant.

Pfeifer said he hopes his invention will spark the interest of carmakers, with whom he is seeking partnerships. His grant from the National Science Foundation is running out, but Pfeifer said he hopes it will be renewed. He said he is also hoping the U.S. Department of Energy will help fund his research, which is why he is working on applying it to hydrogen, another potential alternative fuel source that has been drawing more attention than natural gas.

Pfeifer said he approves of hydrogen and biofuels initiatives, but does not think they can meet the country’s immediate energy needs.

“It’s misleading to believe that this will solve our large-scale problems,” he said. “Hydrogen will not be with us until the year 2020. If (natural gas) became a national goal, we could do this in two or three years.”