July 27, 2006

 

US researchers use corn by-products to generate power

 

 

Corn stover (corn stalks and stems) can be used not only to manufacture ethanol, but to generate electricity directly, according to research from Penn State University whose findings were reported in the journal Energy and Fuels.

 

Bruce E. Logan, the Kappe professor of environmental engineering said the energy industry is now interested in using cellulose to make ethanol. Electricity can be made directly once the sugars are extracted from the corn stover, he said.

 

The project, funded by the USDA and the National Science Foundation, uses a microbial fuel cell to convert organic material into electricity.

 

Research has shown that these fuel cells can generate electricity from glucose and from wastewater and that these cells also can directly generate hydrogen gas.

 

The US corn industry currently produces 250 million tonnes of corn stalks and leaves a year, accounting for a third of all solid waste in the US. Currently, 90 percent of that is unutilised.

 

Corn stover is about 70 percent cellulose or hemicellulose.

 

A steam explosion process releases the organic sugars and other compounds in the corn waste and these compounds are fed to microbial fuel cells.

 

The microbial fuel cells contain two electrodes and anaerobic bacteria that consume the sugars and other organic material and release electrons.

 

These electrons travel to the anode, which flow to the cathode, thus producing a current. Water in the fuel cell contribute 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 bacteria colonies were fed the sugary organic liquid obtained from the steam exploding of corn stover.

 

Thus, the remaining liquid, to be disposed, would cause no problems as there is nothing left to oxidise. The process converts all available energy to electricity. The electrical production is about one watt for every square metre of surface area at about 0.5 volts. A typical light bulb uses 60 watts.

 

Producing electricity from steam-exploded corn stover adds to energy diversity, said Logan.