Volume 10, Number 1
Feb 1986

New Ways to Remove Lignin

Unrelated research projects in Illinois and Wisconsin, the results of which were published in 1985, have turned up new ways of separating cellulose from lignin. Because details are not yet available, the news articles are reprinted below verbatim. (Lignin, the natural "glue" that holds cellulose fibers together and stiffens plant stems, causes paper made of wood pulp to weaken and discolor rapidly if not removed in the pulp mill; but the removal processes are harsh, and shorten the fibers on which the paper's strength depends.)

The first news article, from on Wisconsin (University of Wisconsin Alumni Newsletter) 7:4, November 1985, was sent in by Elizabeth Morse, conservator with the National Park Service in Brookline, Massachusetts.

Pulp Discovery May Revolutionize Paper Mills

Raymond A. Young, a wood chemist, has discovered a new way to process pulpwood that may cut paper mill energy and production costs by 80 percent or more, cause virtually no air or water pollution, and double pulp yields.

"There hasn't been a change like this in the paper industry for 100 years," said Young a Forestry professor. He discovered that combining water, acetic acid, and ethyl acetate creates a remarkable solvent for dissolving lignin--the glue that holds wood fibers together.

Young's method, called ester pulping, not only recycles the chemicals that separate wood fibers, but also produces some of the chemicals needed to process pulp. These innovations dramatically reduce operating costs and pollution.

Young and Biodyne Chemicals, Inc., a Neenah [Wisconsin] firm for which Young consults, are developing an ester-pulping pilot plant expected to produce 10 to 15 tons of pulp per day. He hopes the plant will be on line within six months to a year, possible in the Neenah area. "If all goes well with the pilot plant, most Wisconsin mills will probably incorporate the process in the future," Young predicted. Mills could retrofit the system on existing plants or build new plants that use the ester-pulping method.

Wisconsin leads the nation in the production of high quality paper. Young's discovery comes at a time when industry is hesitant about investing in new mills in the state because of the high cost of energy and pollution control equipment.

For years, scientists have been looking for a better way to pulp wood. Young acknowledged that his discovery owes as much to good fortune as scientific insight.

"I was working with acetic acid as a pulping solvent," Young said, "and was consulting with Kenneth Baierl, a chemical engineer at Biodyne, who was looking at ethyl acetate. My son, Tim, who was helping me, misunderstood directions and added acetic acid to an experiment with ethyl acetate. When we saw bow well the combination worked, I could see the wood chemistry ramifications, and Baierl envisioned bow neatly the system would work in terms of industrial chemical recovery. So here we have a situation where specialists are conducting a systematic inquiry and are fortunate to have just plain dumb luck intervene." (Reporter: Steve Slack)

The second news article describes agricultural research, and gives no indication of whether the process affects the length of cellulose fibers, of course, because digestibility, not paper strength, was the criterion. It is from the Washington Post of November 17, 1985, p. A12

Waste Less, Fed More

Crop wastes such as straw, corncobs and cornstalks can be converted into livestock feed that provides as much food energy as corn, agricultural researchers have found at the University of Illinois at Urbana-Champaign.

If the conversion process can be made economical, it could mean that more of the grain fed to animals could be used for human food instead, increasing the world's food supply.

Scientists have long known that the cellulose fiber in crop wastes is a carbohydrate that contains as much energy as grain starch or sugar. Although humans cannot digest cellulose, ruminant animals such as cattle can.

However, the tougher parts of many plants, such as the stalks, have much of their cellulose chemically bound to a woody substance called lignin. Even cattle cannot digest the cellulose in this form. the Illinois researchers, led by George C. Fahey, Jr., found that if they treated the crop wastes with an alkaline solution of hydrogen peroxide, the same chemical used as an antiseptic, the lignin bonds were broken and the crop wastes became nearly as digestible as corn.

Animals fed a diet heavy with untreated crop wastes lost weight. Similar animals given treated wastes gained weight.

Because 50 percent to 70 percent of a farmer's financial investment in his crop goes to grow the part of the plant that is wasted, the conversion process is economically attractive. However, the cost of drying the wet-treated crop wastes is still too high. Fahey, who reported his findings in the journal Science, said he hopes to develop a less costly alternative.

The removal of lignin with pure enzymes was reported in the April issue of this Newsletter on p. 33.