New technology for papermaking : commercializing biopulping
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Biopulping is defined as the treatment of wood chips with lignin-degrading fungi prior to pulping. Fungal pretreatment prior to mechanical pulping reduces electrical energy requirements during refining or increases mill throughput, improves paper strength, reduces the pitch content, reduces cooking time for sulfite pulping, and reduces the environemntal impact of pulping. Our recent work involved scaling up the biopulping process toward the industrial level, investigating both the engineering and economic feasibility of the technology. We envision the process to be done in either a chip-pile or silo-based system for which several factors need to be considered : the degree of decontamination, a hospitable environment for the fungus, and the overall process economics. Currently, treatment of the chips with low-pressure steam is sufficient for decontamination. Furthermore, a simple, forced ventilation system can be used to maintain the proper temperature, humidity, and moisture content throughout the chip bed, thus promoting uniform growth of the fungus. The pilot-scale trial resulted in the successful treatment of 4 tons of wood chips (dry weight basis), with results comparable to those on a laboratory scale. For mechanical pulping, a 2-week treatment results in approximately 30% energy savings, which, considering the additionai equipment and operating costs, results in an overall savings of US$ 10-20 per ton of pulp in a chip-pile system. Larger, 40-ton trials were also successful, with energy savings and paper properties comparable with the laboratory scale. Application : biopulping technology produces stronger mechanical pulps together with energy savings, resulting in substantial economic savings.