Besides the smell, paper production creates a byproduct called "brown liquor." Although this thick substance is often reused by mills as a fuel source, Swedish electronics experts recently used it to create a new inexpensive battery cathode they say is a better alternative to precious or rare metals.

Most cathodes are made from metals, including rare ones, that drive up the cost for the whole battery. If we want more solar and wind power, we need a cheaper and more environmentally sound way to store it. Olle Inganas, a biomolecular and organics professor from Linkoping University, along with Polish researcher Grzegorz Milczarek of Poznan University of Technology, think they have a solution.

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"Nature solved the problem long ago, Inganas said in a university article about the cathode.

The researchers say they were inspired by the way chemically active molecules called "quinones" transport electrons during photosynthesis. They settled on starting with brown liquor because it contains lignins rich in organic compounds that can be converted to quinones.

To create their cathode, Inganas and Milczarek took lignin derivatives from the brown liquor and combined them with a conductive polymer called "polypyrrole." Together, the materials make for a cathode that's both conductive and can hold a charge. Their paper was published today in the journal Science.

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The new cathode does have disadvantages, though. The most significant is that the battery slowly releases its charge when idle, losing it all within hours. The researchers did find that lignin derivatives performed differently depending on how they were produced. Now the plan is to work on optimizing the batteries by trying out different derivatives.

If — and it's a big "if" — they succeed, brown liquor could very well turn into battery gold.

Photo: Brown liquor waste from paper pulping. Credit: Keith Weller, USDA Agricultural Research Service.