Paper making may take on cleaner look

By LIDIA WASOWICZ, UPI Senior Science Writer  |  Nov. 8, 2001 at 7:40 AM
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Chemists have taken a step toward giving paper making a cleaner look.

Their prototype system, described in the British journal Nature, brightens the prospects of turning wood into paper without waste products of the chemicals used in creating the staple of anyone with a pen, printer or fax machine. The technique, which faces stiff technical hurdles, may not be ready for a commercial debut for a number of years, scientists said.

A mixture of bark and hemp when it was invented by the Chinese sometime around the year 105, paper today is made mostly from wood pulp.

The need for the chemical whitening of paper used for printing or writing arises from the presence of lignin, the "glue" that holds wood fibers together but which turns yellow in sunlight. It must therefore be removed by alternating treatments with acid and alkaline solutions. The wood pulp, boiled under pressure and treated to dissolve its bond with the lignin, turns into cellulose fiber. The mixture is then washed and bleached.

Because the resulting pulp is more than 90 percent water, the water usually is treated before mixing. The new method would curtail the need for such treatment, scientists said.

As it stands, paper mills churn through some 100 million tons of wood pulp each year. The industry uses primarily the oxidizing agent chlorine dioxide to selectively degrade lignin; the process releases millions of tons of chlorinated pollutants, some of which may have health consequences. In 1995, the industry produced 2 trillion pounds of waste, according to figures from the Environmental Protection Agency. Industry officials are quick to point out they are well within EPA standards for air and water quality and they continue to make progress in reducing any environmental impacts from their operations.

One such advance is the new method for delignification proposed by Craig Hill of Emory University in Atlanta, Ira Weinstock of the U.S. Department of Agriculture's Forest Service in Madison, Wis., and colleagues. The technique is based on a catalyst for use with oxygen in water. The catalyst, a polyoxometalate cluster ion, converts lignin into nothing more threatening than water and carbon dioxide.

"Our process is designed to eliminate the production of organic effluent from the bleach plant by converting the lignin to carbon dioxide and water as part of the overall process itself," Hill, a professor of chemistry at Emory, told United Press International. "This is referred to in environmental circles as point-source reduction. That is, elimination of the problem at its source, rather than producing waste and using technology to remediate it."

"Overall, the pulp and paper industry worldwide has, as an ultimate goal, the complete elimination of all organic effluent -- chlorinated or otherwise -- from bleach plants. This goal is far from realization," Weinstock told UPI. "The POM technology, however, is designed to eliminate this problem -- release of organic effluent -- entirely."

Improvements in the process are needed before the paper industry might make the switch, cautioned Terry Collins, professor of chemistry at Carnegie Mellon University in Pittsburgh, who analyzed the findings in an accompanying commentary. For the system to be economically viable, the catalyst must be more efficient and the process of catalyst recovery more refined so it does not become an environmental problem itself, he said.

"The chemistry is indeed very clever; however, many developments in chemistry down the last century have also been very clever and have turned out to be disastrous for the environment," such as using lead as a fuel additive, Collins said in a telephone interview. "The inventors of this technology have to face up to these issues and see if they can resolve them as they make the chemistry better."

At issue are heavy metals.

"This process still involves large amounts of heavy metals so you have to think of how to design it so it can never hurt nature," Collins told UPI.

"Methods for removing metals and salts carried into the system as components of the pulp must be evaluated," Weinstock agreed. "Keep in mind that wood itself contains many metals, including heavy metals, and that quantities of a variety of metals, including many heavy metals, are added to pulp fibers by papermakers as trace components of natural clay fillers."

The technology, called polyoxometalate bleaching, is an outcome of the American Forest & Paper Association's continuing efforts to reduce emissions, said David Friedman, director of AF&PA energy and technology in Washington.

"Traditional bleaching processes use large amounts of water and energy and generate large volumes of wastewater. The ideal bleach plant would produce virtually no effluent, saving chemical feedstock, energy and water," Friedman told UPI. "This new bleaching process under investigation ... strives to provide a cost-effective option for dramatic reductions in effluents from bleach plants."

Even before the advance, the association members had achieved a 44 percent decline in wastewater discharges per ton of production at pulp and paper mills since 1975 and "dramatic" reductions in emissions of chlorinated organic compounds thanks to refined bleaching practices, Friedman said.

Ted Wegner, assistant director of the USDA lab in Madison, pointed out over the past 20 years the pulp and paper industry has spent $12 billion to comply with environmental regulations.

"We've been trying to come up with new technologies that don't produce any byproducts that you need to spend a lot of money on treating to meet clean air and water quality standards," he said in a telephone interview.

The latest answer offers "completely novel chemistry for the field of pulp and paper making," said Bertil Stromberg, director of technology at Andritz-Ahlstrom KMB in Glens Falls, N.Y., a supplier of pulp and paper processing equipment. "I have been part of the industrial consortium directing this work, and the progress made since the idea was first presented is quite dramatic."

Already, several generations of polyoxometalates have been developed, each coming closer to the industry criteria, said Rajai Atallai, former head of the chemistry and pulping unit at the forestry lab, who initiated the program in 1990.

"We can produce pulps equal to or better than some of the best. But can we do it economically?" he said in a telephone interview.

For now, Stromberg doubts it.

"It produces an equally good pulp at about the same cost, if we ignore the capital needed for the extra equipment to make it work," he said. "So as revolutionary a chemistry as it is, the industry is not ready to accept it yet. If the research work can continue for a few more years, it can very well become a widely accepted process for this industry. One problem it faces is the cost and time it will take to get there. With the paper industry in the current economical shape it is in, spending $10 million to $15 million for possible results five years from now is not a likely scenario."

Optimal POM delignification systems are achievable within two to three years, depending on funding, the lead investigators said.

"If successful, the research program currently underway would provide an alternative process option. Implementation, however, will depend upon many factors (global economic issues, industry capitalization, environmental regulation) that are beyond the control of those working to advance the technology as such," Hill said.

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