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Paper mill waste piles up quickly in only a few days at Sappi Fine Paper in Cloquet, Minn.
U researchers find new uses for paper mill waste
By June Kallestad
From eNews, May 13, 2004
We all know the adage "waste not, want not." But is there a way to make the tons of pulp waste generated by paper mills into a want? Researchers at the University of Minnesota, Duluth's Natural Resources Research Institute (NRRI) think they've found it. "We needed to find something that would use truckload after truckload of this stuff day after day, [because] current disposal methods are costly or cannot keep up with the amount of waste that's being generated," says Pat Donahue, NRRI forest products researcher. Minnesota paper mills generate more than 250 tons or more than 12 truckloads of waste a day. In Wisconsin, the problem is much bigger-with some 3,000 tons or about 150 truckloads. The most common method of disposal is spreading the waste on agricultural fields as a soil additive because it's made up of inorganic fibers and mostly clay minerals. The least expensive option is to burn it. However, burning requires a lot of energy because the waste retains 50 percent of its water content after it's pressed. And land filling is the most expensive option because landfill space is getting harder to come by. Donahue and his colleagues discovered that with the right binding additive, the waste pulp could be transformed into flooring tiles, siding, and other durable building products. "We tried many different combinations of binding materials on different products until we found a cement-based process developed at the University of Philippines Los Banos that is working very well," he explains. But instead of cement, NRRI scientist Matt Aro used Ceramicrete, a phosphate and magnesium oxide powder that is nonporous and can have compressive strengths higher than concrete. When mixed with the inorganic fiber waste from the mills, it can be cast into any shape. It's also stronger, lighter, non-flammable and takes less energy to make than concrete. "The thing to remember is, a lot of energy went into this [waste] material already," says Donahue. "It's already been extracted, mined, processed, transported... . We really shouldn't just throw it away." The researchers are currently working with paper mills in Minnesota and Wisconsin to further study their waste properties and to refine the processing techniques for their new method. The ultimate goal, says Donahue, is to create products that consumers can buy in stores. The U.S. Department of Agriculture Forest Service is funding this research. The Wisconsin Business Innovation Center, the Forest Service, and the Wisconsin Department of Natural Resources are partners in the project.