Corncobs Store Gas for Natural Gas Vehicles

Natural gas is an abundant fuel that is domestically produced or comes from friendly places like Canada and Mexico. It's clean burning and can be used in existing internal combustion engines with minimal modifications. The downside is storing gas aboard vehicles.

Today, natural gas is stored either as compressed natural gas (CNG) under high pressures, typically 3,000 to 10,000 psi, or as liquefied natural gas (LNG) at cryogenic temperatures, about -260 degrees F. Both of these storage techniques require expensive tanks that are not very well suited for smaller vehicles because they're heavy and take up considerable space.

There is a third alternative: absorbed natural gas (ANG). As its title implies, ANG storage is accomplished by absorbing the gas in a porous material, a process that enables gas molecules to adhere to a microporous solid material with the gas released when needed. Activated charcoal is a good absorbent because it is porous and thus provides a very large surface area for absorbing large quantities of gas.

By using ANG technology, the same volume of gas can be stored in a given sized container, but at a much lower pressure. This translates to reduced vehicle weight because a lighter weight container can be used. Or alternatively, a greater volume can be stored at the same pressure, which translates to increased range.

ANG offers several advantages over CNG and LNG. As mentioned, natural gas can be stored at lower pressures compared to CNG, notably 500 to 1000 psi versus 3500 to 10,000 psi. Lower pressure means significant infrastructure cost savings for filling stations, lower fuel costs for motorists, and more efficient use of a vehicle's space. Because less filling pressure is required, car owners could install a modest compressor at home and refuel their vehicles from the home's natural gas supply.

The really big benefit, however, is the ability to store gas in low pressure tanks. Rather than bulky cylindrical tanks that can take up an entire car trunk, ANG tanks could be configured in virtually any shape. For instance, slim thin-walled rectangular tanks could be placed beneath a car without the need to take up space inside the vehicle.

ANG also opens up the possibility of using natural gas in more unconventional vehicles like motorcycles and motor scooters. For instance, Angstore Technologies Ltd. in Israel has converted an Indian-built motor scooter to run on ANG, a first. The company plans to begin serial conversions of motorcycles this year. Angstore's parent company, Energtek Inc. in New York, is working with the Philippine Department of Energy and the Philippines National Oil Company Exploration Corp. in a program to convert very popular three-wheel vehicles to natural gas with ANG storage.

ANG's compatibility with small two and three vehicles could bring natural gas to the fastest growing segment of the world's automotive market, with about 200 million two and three wheelers in Asia alone. Besides being a less expensive and more readily available fuel, natural gas could help clean up the air pollution found in many Asian cities.

Some unusual materials are being considered for absorption such as waste corncobs, which are converted to activated carbon for ANG use. Researchers at the University of Missouri-Columbia and Midwest Research Institute in Kansas City have created carbon briquettes made from corncobs that are abundantly available as a waste product in the Midwest. Missouri alone could supply the raw material for more than 10 million natural cars per year. This could bring double benefits: corn kernels for ethanol production and corncob for ANG tanks.

Corncob-based briquettes can store natural gas at an unprecedented density of 180 times their own volume and at one-seventh the pressure of conventional CNG tanks. The walls of the nanoporous carbon adsorb methane molecules as a high-density fluid. In action, the strong attractive force in the narrow pores lowers the energy of the molecules so they can be packed much more closely than in the absence of the carbon.

Briquettes could store natural gas at only 500 psi, the same pressure found in natural gas pipelines. This technology has been incorporated into a test bed installed on a pickup truck used regularly by the Kansas City Office of Environmental Quality. Researchers are now focusing on the next generation briquette that will store even more natural gas and cost less to produce. They also believe this next generation of briquette might even be able to store hydrogen.