Recent developments in biopulping technology at Madison, WI

Biopulping is defined as the treatment of wood or other lignocellulosics with a "natural" lignin-degrading fungus prior to pulping. Research consortia made up of the USDA Forest Service, Forest Products Laboratory (FPL) in Madison and the Universities of Wisconsin and Minnesota have evaluated biopulping from a small laboratory scale to a 50-ton semi-commercial scale over the past 12 years. The investigations were supported in part by 23 pulp and paper and related companies and the Energy Center of Wisconsin. The State University of New York, College of Environmental Science and Forestry has also joined as a partner in this research. The research established that biopulping substantially lowers the electrical energy required for mechanical pulping (or increases mill throughput), improves certain strength properties (reducing the need to augment with chemical pulps), and reduces environmental impact. Biopulping also reduces the pitch content of the pulp. At a pilot scale, we have developed methods for decontamination of wood chips, cooling, and fungal inoculation sequentially in screw conveyers, and controlling temperature and moisture throughout the chip pile. Mill-scale refining of fungus-treated chips gave results similar to those obtained using the laboratory-scale bioreactors. With this information, a complete process flowsheet has been established for the commercial operation of the process. Based on the electrical energy savings and the strength improvements, the process economics looks very attractive. Several independent economic evaluations of biopulping have now been completed by both university and industry economists and engineers and are in agreement. Based on energy savings and reduction in kraft pulp in the final product, substantial savings can be realized. The additional benefits of increased throughput, and reduced pitch content and environmental impact improve the economic picture for this technology even further.