Soil Development in a Coal Waste, Slag and Sludge Artificial Topsoil Mix

Abstract

Waste disposal has become a major concern for industries that create a large amount of by-products due to the cost of landfill and environmental responsibility. Beneficial re-use of these by-products which contain resources for other industries, will solve some of these problems. An artificial soil mix has been created out of ironmaking and sewage wastes, for use in a revegetation program to improve the BHP Steelworks site in Australia. Coal washery refuse, blast furnace slag and sewage sludge have been combined to form a topsoil which is placed on waste mounds and revegetated. Field trials were established to evaluate the soil forming characteristics of this artificial media. The fine fraction (<2mm) of the particle size distribution decreased from 71% to 64% in one year, showing evidence of weathering and particle breakdown. Bulk density remained the same (1.0 g/cm 3) in a two year comparison. The pH of the soil mix declined from 7.6 to 7.1 in one year. Native tree growth in the soil mix was very good, although comparisons could not be made with real soil. The long term viability of the soil mix in relation to nutrient cycling could not be extrapolated with only two years of data. The potential is promising for the use of this soil substitute in urban landscaping, land restoration and revegetation, and opportunities for further research are available.