Is there a green way to stop paper turning yellow?

It's because newsprint is made from a mechanical wood pulp, produced from ground wood that goes through very little chemical processing. The trouble is, this pulp contains lignin, a natural part of the wood that yellows when it's exposed to light and air.

Stopping the paper from turning yellow is a complex chemical problem. But it's one that's certainly worth solving. The pulp and paper industry has been trying to find a solution for decades, but progress has been slow.

Chemists David Griller and Tito Scaiano tackled the problem from the chemical end.

"We took models of this lignin to find out how sunlight breaks it up, producing the yellow color," Griller says.

Scaiano explains, "While it may take a week or a month for the paper to turn yellow, the individual reactions that are responsible for this may take place in less than a millionth of a second. It's critical to do the basic research to understand why this happens."

"If we know why the yellowing happens, we can identify materials to stop it," Griller adds.

It's no surprise that the pulp and paper industry went to the National Research Council for help. During the two chemists' time there, Scaiano (now at the University of Ottawa) and Griller (now with Peat Marwick) built up the world's most advanced equipment for the study of short-lived intermediates, which include those that make paper yellow.

At present, newsprint made from mechanical pulp costs about $500 a tonne and makes use of 90 percent of the wood from a tree. Higher quality papers - those that have had the lignin removed - cost about $1,000 a tonne. To make fine paper, a chemical treatment is required that wastes up to 50 percent of the wood, and the processing harms the environment.

"If we could do something for $200 a tonne to stop the yellowing, the price of mechanical pulp paper would go up from $500 to $700," says Scaiano. That's still 30 percent less than the cost of fine paper, "and there'd certainly be a market for lower grade paper that doesn't yellow."

If there were more uses for mechanical pulp, there would be fewer trees cut and less pollution. New markets would also open up for a major Canadian export.