Future Batteries Could Run on Brown Liquor

The cathode is often one of the most expensive components of a battery-especially if it's made of cobalt or precious metal. A Swedish scientist may have discovered a way to replace pricey metal cathodes with a goopy byproduct of paper processing known as "brown liquor."

Brown liquor is the result of the Sulfite process for producing wood pulp. Wood chips are bathed in sulfurous acid in pressure vessels to extract the lignin and break down the wood fiber. The brown sludge is a mix of spent chemicals, lignin, and hemicellulose. It is often burned to generate steam in the paper mill, but it apparently makes a decent low-cost cathode as well.

Olle Inganas, Professor of Biomolecular and Organic Electronics at Linköping University in Sweden, and Grzegorz Milczarek, a researcher at Poznań University of Technology in Poland made discovery which was published today in the journal Science.

"Nature solved the problem long ago," Inganas is quoted in a University article. He credits the photosynthetic process as inspiration for the discovery. Brown liquor is primarily broken-down lignin, part of the cell wall. Lignin can be further broken down further into quizones, electrically conductive molecules that transport electrons during photosynthesis. By encasing the sludge in a conductive polymer, the team created an inexpensive cathode—with quizones carrying electrons across the semi-permeable membrane—and capable of holding a charge. At least for a while.

The current prototype continually discharges when it is idle, running down in a matter of hours. The team believes they can stabilize the cathode by fiddling with the specific lignin derivative and create a low-cost, green battery. [LIU via Discovery via TreeHugger - Image: Keith Weller, USDA Agricultural Research Service]