Nippon Paper Industries (NPI) and Jomo Landscape Construction, Ltd. (Located in Yoshioka Town, Kitagunma Gun, Gunma Prefecture. President: Koji Takahashi) have jointly developed a method for manufacturing artificial soil from power plant fly ash. This soil will be used to plant greenery over bare, man-made slopes.

 

NPI is currently carrying out a "Zero Discharge Campaign" in an effort to reduce its industrial waste to less than 0.2% of the company's total production volume. As one part of this campaign, NPI has been working on ways to use the fly ash generated as a by-product of the combustion of coal in the process of power generation. NPI generates about 150,000 tons of power plant fly ash every year. This latest effort follows on the heels of a successful project last year in which NPI worked together with the Tokyo University of Agriculture and the city of Abashiri, Hokkaido to use fly ash for dehydration of sewage sludge.

 

Fly ash is almost completely devoid of organic substances, and would not normally perform the functions of ordinary soil, but when it is mixed with sewage sludge (which is rich in organic substances) and composted, it works as useful soil. However, over 90% of all power plant fly ash is a powdery substance with a particle size of less than 0.1 mm. If composted in such a fine state, proper aeration and fermentation would not occur. For this reason, it was necessary to compact the powder into pellets. Uniformly shaped round and cylindrical pellets that were used at first, however, did not mix well with the sewage sludge. NPI solved the problem by developing pellets of irregular shapes and sizes, with sharp angles and projections. These yielded artificial soil that was appropriate for planting greenery on the bare slopes that result from construction projects, etc. Because fly ash pellets absorb odors, this technology offers the added benefit of reducing the stench of sewage.

 

Soil produced in this manner has already been used in three large experimental projects, and it supports the growth of greenery every bit as well as other types of soil.

 

In addition to the fly ash project, NPI and Jomo Environmental Engineering, Ltd. have also successfully developed a method of producing artificial soil using carbon compounds generated from sewage sludge and the sludge byproducts of NPI's paper making process. This artificial soil is already used in the construction technique known as the PMC method. The use of power plant fly ash is under consideration for areas in the Kyushu region.

 

The irregularly shaped fly ash pellets developed in connection with this project may also have other applications. Research is now being planned to investigate their possible use in soil improvement.