Update on Biopulping Commercialism, 2000 Pulping / Process & Product Quality Conference Proceedings

G. M. Scott, M. Akhtar, T. K. Kirk--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 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 33% energy savings and a 5% reduction in kraft pulp in the final product, a savings of about $5 million each year 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. It has now passed through the science and the engineering evaluation phases, and is in the realm of business.

One of the chemical companies has already agreed to produce and supply fungal inoculum on a commercial scale. No adverse effects of lignin-degrading fungi on humans have been reported in the literature. These fungi are natural wood decayers. However, a biopulping operation would entail producing substantial amounts of fungus in a pile on a routine basis. For that reason, the best biopulping fungus, Ceriporiopsis subvermisprora, was tested by professionals for adverse effects on humans. It was concluded that the fungus is safe for use on a commercial scale. One of the paper

companies has hired a professional company to look into the effects of the technology on the environment. The company is currently analyzing VOC’s given off during biopulping and comparing them with those from a standard chip pile storage. This paper will summarize biopulping process development and commercialization.