Français	Contact Us	Help	Search	Canada Site

Home	Site Map	What's New	About Us	Registration


	The Application of Biotechnology to Industrial Sustainability
	Industrial Sustainability Through Biotechnology

Pulp and paper

The pulp and paper industry is very capital-intensive with small profit margins. It must meet increasing demand for pulp and paper and, at the same time, comply with increasingly stringent environmental regulations. Driven by market and environmental demands for less chlorinated products and by-products, it is the fastest-growing market for industrial enzymes. In the United States, this market is projected to grow by 15% a year for the next ten years.

Enzymes improve processing time

Enzymes such as cellulases and hemicellulases partly break down cellulose and can improve drainage of water from the pulp and thus the speed of paper machine operation, which depends in part on the drainage rate. As this tends to be lower for recycled fibers, the production rate declines as the recycled fiber content increases. These enzymes are now used commercially as drainage aids. The enzymes remove the finest fibers, allowing water to drain away faster, cutting the processing time, and reducing the energy required to dry the paper. According to Olli Jokinen of Genencor International, which produces the enzymes, machine speed can be increased by up to 7%." Moreover, the machines run better, and the wastewater system is cleaner. In trial runs, energy input per ton of pulp was reduced by as much as 7.5%."

In paper making, various processes are used to separate the cellulose fibers from the lignin in wood to form a slurry (pulp) that is then processed into paper and board. Existing chemical pulping operations create a great deal of pollution. Biopulping, which involves the treatment of lignocellulosic materials with lignin-degrading fungi, has been shown to result in energy savings and strength improvements. Enzymes are now also being incorporated into the pulping process, where they offer a number of advantages.

The structure and chemical composition of pulp fibers are of paramount importance for paper strength and other properties. Enzymes can be used to reduce fiber coarseness, increase paper density and smoothness, and improve appearance. Most pulp is produced using the kraft process. Kraft pulps have a characteristic brown color, which must be removed by bleaching before manufacturing paper for writing or other products for which appearance is important. Chlorination is traditionally used, but pulp manufacturers are turning to other techniques because of consumer resistance and environmental regulations.

According to studies conducted in Finland, hemicellulases (mainly xylanases) improve bleaching. They are now being used commercially in Scandinavia, Canada, the United States, and Chile. Treating kraft pulps with xylanases significantly reduces chemical consumption with almost no loss in pulp yield or quality. A new enzyme that is better suited to the temperatures and pH found in pulp processing has also been developed in Israel and successfully tested in a large-scale trial.

Using bacteria to remove by-products

Adding polymers to paper stops fibers from becoming waterlogged and gives the paper wet strength. However, the polymer production process creates contaminants which reduce its effectiveness. Carbury Herne Limited and Hercules Inc. have developed a bioprocess for removing these by-products. Two strains of bacteria are used to digest the by-products which are then washed out of the polymer before it is applied to the paper. "Apart from being much more environmentally acceptable, this treatment is much less expensive than developing a new product or a new manufacturing process to do the same job", says Professor Howard Slater, chairman of Carbury Herne Limited. The process has now been adopted at production scale at two plants that make packaging paper for food liquids. As the bioreactors were built into existing production lines, costly redesign of the production process was avoided.


		Created: 2005-06-07 Updated: 2005-10-11	Top of Page	Important Notices