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Posted 02.19.07


'Fractal Pore Spaces' Fuel Low Emission Breakthrough

COLUMBIA, MO - Researchers at the University of Missouri-Columbia (MU) and Midwest Research Institute (MRI) are testing an innovative alternative fuel technology in a pickup truck owned and operated by the Kansas City Office of Environmental Quality. This technology may revolutionize the capacity of natural gas to power vehicles.

Natural gas truck prototype.Current natural gas vehicles are equipped with bulky, high-pressure tanks that take up premium cargo space, such as the trunk of a car. This new technology, however, enables natural gas to be stored in a smaller, low-pressure tank that can be shaped into a rectangular form and mounted under the floor of a car. What makes this possible is an MU discovery that fractal pore spaces (spaces created by repetition of similar patterns at different levels of magnificent) are remarkably efficient at storing natural gas. The scientists found a way to "bake" corncobs into carbon briquettes that contain fractal pore spaces and then use the briquettes to store natural gas in a low-pressure tank. MU and MRI researchers are now testing a prototype of this tank in the Kansas City pickup. They hope this will lead to the design of low-pressure tanks that solve the cargo space problem posed by high-pressure tanks.

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"This technology could make natural gas an attractive alternative fuel for smaller vehicles," said MU Chancellor Brady Deaton. "The research partnership here exemplifies how scientists from very different fields can work together to conduct truly fundamental research in new materials with the explicit goal of having the results of the research solve problems for people."

The test pickup has been on the road since mid-October. Researchers are monitoring the technology's performance by collecting data to evaluate the mileage range per fill-up; pressure and temperature of the tank during charging/discharging; charging/discharging rates under various fueling/driving conditions; and longevity of the carbon briquettes.

"Having a prototype of this technology operating in the day-to-day work environment is significant," said James L. Spigarelli, president and CEO of Midwest Research Institute. "It symbolizes the power of collaboration and the ability of MU and MRI researchers, working together, to make a scientific discovery; to transfer that discovery to a technology, in this case a fuel tank technology; and then move that technology closer to commercialization. Although the team's work is not yet complete, this technology development comes at a fortuitous time as many researchers strive to find multiple alternatives to address the nation's energy challenges."

Kansas City has been a leader in natural-gas-powered vehicles, ranging from utility trucks to shuttles at the Kansas City Airport. The city operates more than 200 natural-gas vehicles under the supervision of Central Fleet Manager Sam Swearngin, who has been instrumental in forging this venture between Kansas City and the MU-MRI team.

"The City of Kansas City is the undisputed champion of alternative fuel vehicles in this region, and we are pleased to have the opportunity to be on the ground floor of this developing new technology," said Kansas City Mayor Kay Barnes.

This project was funded by a $600,000 grant from the National Science Foundation's program Partnerships for Innovation, which has the goal of stimulating the transformation of knowledge created by universities into innovations that create new wealth, build strong local, regional and national economies and improve the national well-being. Additional funds totaling more than $400,000 came from MU, MRI, the U.S. Department of Energy and the U.S. Department of Education.

A secondary goal of the Partnership for Innovation is to meet the broad workforce needs of the national innovation enterprise. The collaborative effort between MU and MRI has afforded a number of university students the opportunity to receive hands-on training for a career in research and development. As a result of the exchange, MRI recently hired an MU graduate and a Lincoln University graduate associated with the project team.

The MU-MRI collaborative is part of a larger cooperative effort called the Alliance for Collaborative Research in Alternative Fuel Technology (ALL-CRAFT), which includes as partners Lincoln University; DBHORNE, LLC; Renewable Alternatives, LLC; the Missouri Biotechnology Association; the Clean Vehicle Education Foundation; the Missouri Department of Natural Resources; and the City of Columbia, Mo. ALL-CRAFT also worked in cooperation with the Kansas City Regional Clean Cities Coalition (KCRCCC).

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MRI is an independent, not-for-profit research organization with 1,800 employees nationwide. Established in 1944, MRI performs research for government and industry in national defense, energy, life sciences, engineering and other areas. With headquarters in Kansas City, MRI also has facilities in Palm Bay, Fla., Frederick, Md., and Rockville, Md. MRI has managed the National Renewable Energy Laboratory (NREL) in Golden, Colo., for the U.S. Department of Energy since 1977. For more information, visit

MU-MRI Low-Pressure Tank Fact Sheet

- The MU-MRI low-pressure natural gas tank uses carbon briquettes made from corncobs to store natural gas. The walls of the nanoporous carbon adsorb methane molecules as a high-density fluid. The strong attractive force in the narrow pores lowers the energy of the molecules so that they can be packed much more closely than in the absence of the carbon. Such a tank is called an adsorbed natural gas (ANG) tank.

- The carbon briquettes can store 180 times their own volume of natural gas, or 118 g of methane per liter of carbon, at 500 pounds per square inch (psi). The best previous carbon could only store 142 times its own volume at 500 psi pressure. The target set by the U.S. Department of Energy is 180 times the storage a material's own volume. The MU-MRI carbon reaches this target for the first time.

- A conventional high-pressure natural gas tank operates at 3600 pounds per square inch (psi), whereas this low-pressure tank operates at 500 psi. This enables flexibility in tank design because high-pressure tanks require bulky, cylindrical walls, whereas the low-pressure tank can use thinner walls in a variety of shapes. The pressure of 500 psi equals the pressure in natural gas pipelines, which eliminates costly compression of natural gas from 500 psi to 3600 psi in CNG tanks.

- The technology being tested in this tank would enable car manufacturers to design long, slim, low-pressure tanks to replace the bulky high-pressure tanks in current natural gas vehicles. This would enable them to place the tank underneath the body of the car, whereas the high-pressure tanks are usually placed in a car's trunk, reducing vehicle cargo space.

- Corncob is an abundant, low-cost, renewable raw material in the Midwest, allowing for production of ANG tanks from domestic sources. The state of Missouri alone could supply the raw material for ANG tanks of 10 million cars per year. Corn could thus serve the alternative fuel economy in two distinct ways - corn kernels for bioethanol production, and corncob for natural-gas tanks.

Source: Calculations by Peter Pfeifer, MU professor of physics, using data from the Corn Refiners Association,

Natural Gas Vehicle Facts

Natural gas is one of the cleanest burning alternative fuels available.
- In light-duty applications, air emissions from natural gas vehicles are lower than emissions from gasoline-powered vehicles. Carbon monoxide and nitrogen oxides, smog-producing gases, are reduced by more than 90 percent and 60 percent, respectively. Carbon dioxide, a greenhouse gas, is reduced by 30 to 40 percent.

- In medium- and heavy-duty applications, natural gas engines have shown a more than 90 percent reduction of carbon monoxide and particulate matter and a more than 50 percent reduction of nitrogen oxides, relative to commercial diesel engines.
Source: U.S. Department of Energy, Energy Efficiency and Renewable Energy, Alternative Fuel Vehicles,

Most natural gas used in the U.S. is domestically produced.
- In 2004, U.S. net imports of natural gas represented only 15 percent of the total amount used, with almost all imports coming from Canada.
Source: U.S. Department of Energy, Energy Efficiency and Renewable Energy, Alternative Fuel Vehicles,

Natural gas is cheaper than gasoline and diesel on an energy-equivalent basis.
- The national average cost of compressed natural gas (CNG) was 94 cents cheaper than gasoline on an energy-equivalent basis, according the Clean Cities Alternative Fuel Price Report in June 2006. Gasoline was $2.84 per gallon, diesel was $2.98 per gallon, and CNG was $1.90 per gasoline gallon equivalent (GGE).
Source: U.S. Department of Energy, Energy Efficiency and Renewable Energy report,

Natural gas can be produced from renewable sources such as landfills.
- As municipal solid waste decomposes, it produces carbon dioxide and methane. That methane, the principal component of natural gas, can be captured by landfill gas energy facilities and combusted for energy.
Source: Energy Information Administration,

- Uncaptured methane is a greenhouse gas that is more than 20 times more potent than carbon dioxide.
Source: U.S. Environmental Protection Agency, Landfill Methane Outreach Program,

- Capturing methane from all U.S. landfills is equivalent to removing the annual greenhouse-gas emission from 50 million cars, or planting forest on an area 2 times the area of Missouri every year, and could power 4 million homes or 4 million cars annually ("pollutant to renewable energy").
Sources: U.S. Environmental Protection Agency, Landfill Methane Outreach Program, and; Additional calculations by Peter Pfeifer, MU professor of physics

Natural-gas fueled vehicles are functionally comparable to conventionally fueled vehicles.
- Horsepower, acceleration and cruise speed in natural-gas-powered vehicles are comparable to equivalent conventionally fueled vehicles.
- Approximately one of every five new U.S. transit buses is powered by natural gas.
Source: U.S. Department of Energy, Energy Efficiency and Renewable Energy, Alternative Fuel Vehicles,

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