Move Over Prius: Here Comes the Corncob Car
Corncob briquettes could prove the breakthrough that makes methane-powered passenger cars viable.
By Andrea Quong
Hybrids, make way.
In a breakthrough that could bring methane-fueled passenger cars closer to being a fixture in American garages, researchers have created a way to store methane gas in slimmer, flatter fuel tanks, obviating the need for the bulky gas compression cylinders that take up precious trunk space and tend to turn off mainstream consumers.
The technology, which was announced last month, uses carbon briquettes made from corncobs to store methane, the main component in natural gas, at a density of 180 times their volume and at one seventh the pressure of conventional methane gas tanks. The storage system is the first to meet the U.S. Department of Energy’s storage density target of 180-to-1 by volume, set in 2000, said Peter Pfeifer, principal project leader and professor of physics at University of Missouri, Columbia.
“With this technology, we can build a flat and compact tank that can fit under the floor and make natural gas a feasible, more widely attractive alternative for passenger cars,” Mr. Pfeifer said.
A joint effort of scientists and engineers at the University of Missouri in Columbia and the Midwest Research Institute in Kansas City, the patent-pending technology adds methane to a growing list of alternative energy technologies that are being explored in every permutation, from ethanol generated from cow patties, algae, or switchgrass to fuels brewed from leftover restaurant grease.
Among alternative fuels for cars, methane is one of the cleaner burning options, releasing less carbon dioxide than gasoline. “While it does not solve all of the greenhouse gas emission problems people worry about, it reduces carbon dioxide output in heavy duty vehicles by 90 percent, compared with regular gasoline,” said Mr. Pfeifer.
Mr. Pfeifer and his colleagues, however, used corncobs, for the first time, to produce briquettes that are shot through with networks of molecular-sized nanopores. These microscopic pores are what enable the briquettes to store natural gas or methane at an unprecedented density, he said. The storage system also allows methane to be stored at a lower pressure of 500 pounds per square inch – the same as in natural gas pipelines—helping carmakers fashion fuel tanks in any shape. The technology is being road-tested on a pickup truck, one of a fleet of 200 natural gas vehicles operated by Kansas City, according to the National Science Foundation, which helped fund the research.
Corncobs, used to fashion the fuel storage system but not used for fuel themselves, are plentiful in the Midwest. By Mr. Pfeifer’s estimate, the state of Missouri could supply enough corncobs to fuel 15 million cars a year.
Current technology relies on large cylindrical tanks that compress natural gas to a pressure of 3600 pounds per square inch. And that can take up an entire trunk. In the United States, where some cities have invested in larger vehicles like garbage trucks and municipal buses that don’t have a space problem, methane-fueled passenger cars are few. Only Honda offers a methane-fueled passenger car, a version of the Civic, Mr. Pfeifer said. In Europe, where the consumer market is friendlier, Volvo and Fiat both make versions of methane or methane-and-gasoline hybrid passenger cars.
Such cars depend for the most part on natural gas, a non-renewable resource that’s extracted mainly from U.S. or Canadian gas fields. Renewable methane, the main ingredient in natural gas, can be produced from feedlots or landfills, where it’s already being used to generate electricity. But that depends on whether or not the U.S. government decides to throw its weight behind funding such research.
“The whole natural gas infrastructure exists already,” said Mr. Pfeifer, whose research was funded by a $600,000 grant from the National Science Foundation and a $500,000 combined grant from the University of Missouri and the Midwest Research Institute. “I really see no obstacles, technical or any other kind, except for peoples’ attitudes that [if something] isn’t visibly broken, why fix it.”
With federal dollars flowing into hydrogen fuel cell research, industry interest, a la Toyota or General Motors, may be the best hope.
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