New Aspen Could Revolutionize Pulp And Paper Industry

The research team, led by Professor Vincent Chiang [pronounced "Chang"], has introduced a gene into Populus tremuloides, commonly known as quaking aspen, that cuts the amount of lignin produced by the tree nearly in half. Lignin, a component of all wood, must be chemically separated from cellulose to make the pulp used in paper production. The chemical, energy, and environmental costs of removing lignin have traditionally been enormous.

The transgenic aspen saplings have other advantages to industry that came as a complete surprise to the researchers: They produce up to 15 percent more cellulose. And they are remarkably fast-growing, even for a fast-growing tree like aspen.

Cellulose is the main component of pulp, and in regular aspen, as well as other tree species, the lignin:cellulose ratio is about 1:2. In the genetically engineered aspen, the ratio is roughly 1:4.

This could translate into huge gains for industry. According to Chiang, manufacturers could see an increase of 15 percent more pulp from the same amount of wood. "And the people in pulp mills jump up and down if they have a 1 percent increase," he said. "If you look at the effect this could have on the industry worldwide, we're talking billions of dollars."

In addition, the trees have the added advantage of having essentially the same lignin structure as regular aspen, so the lignin can be removed through existing pulping processes, but using reduced amounts of chemicals and less energy. And so far, they are extremely fast growing, a characteristic sought by tree producers. In the greenhouse, some transgenic aspen are 30 percent taller than the control group.

Chiang can only guess as to why they are growing so fast. For trees, making lignin takes a lot of energy, and he theorizes that the trees somehow transfer the energy saved from lignin production to other areas, such as enhanced growth and cellulose production.

U.S. and international patent applications have been filed on the transgenic aspen, and Michigan Tech is negotiating licensing agreements with a major wood-products corporation.

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Coauthors of the Nature Biotechnology paper are graduate students Wen-Jing Hu and Juhau Lung, Dr. Scott A. Harding, Dr. Chung-Jui Tsai, and Research Scientist Jacqueline Popko, all of Michigan Tech's School of Forestry and Wood Products; John Ralph, of the University of Wisconsin-Madison; and Douglas D. Stokke, of Iowa State University.