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Corn waste potentially useful for more than ethanol

Corn waste potentially useful for more than ethanol

Corn waste potentially useful for more than ethanol
Penn State
July 19, 2006

After the corn harvest, whether for cattle feed or corn on the cob, farmers usually leave the stalks and stems in the field, but now, a team of Penn State researchers think corn stover can be used not only to manufacture ethanol, but to generate electricity directly.




“People are looking at using cellulose to make ethanol,” says Dr. Bruce E. Logan, the Kappe Professor of Environmental Engineering. “You can make ethanol from exploded corn stover, but once you have the sugars, you can make electricity directly.”



Logan’s process uses a microbial fuel cell to convert organic material into electricity. Previous work has shown that these fuel cells can generate electricity from glucose and from municipal wastewater and that these cells can also directly generate hydrogen gas.



Corn stalks and leaves, amassing 250 million tons a year, make up a third of the total solid waste produced in the United States. Currently, 90 percent of corn stover is left unused in the field. Corn stover is about 70 percent cellulose or hemicellulose, complex carbohydrates that are locked in chains. A steam explosion process releases the organic sugars and other compounds in the corn waste and these compounds can be fed to microbial fuel cells.


The microbial fuel cells contain two electrodes and anaerobic bacteria — bacteria that do not need oxygen — that consume the sugars and other organic material and release electrons. These electrons travel to the anode and flow in a wire to the cathode, producing electrical current. The water in the fuel cell donates positive hydrogen atoms that combine with the electrons and oxygen to form water.



The microbial fuel cells were inoculated with domestic wastewater and a nutrient medium containing glucose, the researchers report in the journal Energy and Fuels. Once established, the bacteria colonies were fed the sugary organic liquid obtained from steam exploding of corn stover.



The researchers, who include Logan, Yi Zuo, Penn State graduate student in environmental engineering, and Pin-Ching Maness, senior scientist, National Renewable Energy Laboratory, report that “the conversion of organic matter to electricity, on the basis of biological oxygen demand removal, was relatively high with greater than 93 percent of the biological oxygen demand removed.”



In essence, there is no organic matter left to cause problems when disposing of the remaining liquid because there is nothing left to oxidize. The process converts all the available energy to electricity. The electrical production is about one watt for every square meter of surface area at about 0.5 volts. A typical light bulb uses 60 watts. To increase wattage, the surface area needs to increase. To increase voltage, fuel cells can be linked in series.



“Producing electricity from steam exploded corn stover adds to the energy diversity of our portfolio,” says Logan. “Electricity can be used to pump water uphill for later use, directly run light, heat and equipment or electrolyze water to create hydrogen.”



The Penn State researcher and colleagues have also used microbial fuel cells and wastewater to produce hydrogen gas directly.





Soybean biodiesel has higher net energy benefit than corn ethanol – study
The first comprehensive analysis of the full life cycles of soybean biodiesel and corn grain ethanol shows that biodiesel has much less of an impact on the environment and a much higher net energy benefit than corn ethanol, but that neither can do much to meet U.S. energy demand.



High oil prices fuel bioenergy push High oil prices and growing concerns over climate change are driving investment and innovation in the biofuels sector as countries and industry increasingly look towards renewable bioenergy to replace fossil fuels. Bill Gates, the world’s richest man, has recently invested $84 million in an American ethanol company, while global energy gluttons ranging from the United States to China are setting long-term targets for the switch to such fuels potentially offering a secure domestic source of renewable energy and fewer environmental headaches.

Biofuels can replace about 30 percent of fuel needs With world oil demand growing, supplies dwindling and the potential for weather- and conflict-related supply interruptions, other types of fuels and technologies are needed to help pick up the slack. A group of experts in science, engineering and public policy from the Georgia Institute of Technology, the Imperial College London and the Oak Ridge National Laboratory recommend a comprehensive research and policy plan aimed at increasing the practicality of using biofuels and biomaterials as a supplement to petroleum. The review article, called “The Path Forward for Biofuels and Biomaterials,” appears in the Jan. 27 issue of Science.

Ethanol more energy-efficient than oil, finds study
Using ethanol — alcohol produced from corn or other plants — instead of gasoline is more energy-efficient than oil say researchers at the University of California, Berkeley. In a study published in Friday’s issue of the journal Science, Berkeley scientists show that producing ethanol from corn uses much less petroleum than producing gasoline.

Congress deals blow to bioenergy market
In a set back to the growing biofuels market and American energy consumers, House Majority Leader John Boehner said Monday he will not push legislation to reduce the U.S. tariff on ethanol imports. Thus, the United States will keep its 54-cent-a-gallon tariff on imported ethanol despite a warning from the Department of Energy that domestic ethanol supplies will fall short this summer and will need to reply on foreign fuel.

This is a modified news release from Penn State