Using South African sulfide-enriched coal processing waste for amelioration of calcareous soil: A pre-feasibility study

Abstract

Coal mining in South Africa is an important economic activity but it generates large volumes of pyrite-bearing wastes in the form of fine coal slurry and discards. These pose a significant acid rock drainage risk. Researchers at the University of Cape Town have developed a multi-stage separation process which separates the coal slurry into different fractions: saleable coal, a sulfide-rich fraction, and a sulfide-lean fraction. This was done with a view to enhancing the material value and producing streams suitable for down-stream re-purposing to avoid disposal and concomitant environmental risks. This paper explores the potential for using sulfide-enriched fine coal waste to ameliorate calcareous (enriched in calcium carbonate) and alkaline soils in the South African context, through a pre-feasibility study focusing on technical viability, local market applications and mine-to-market transport costs. Consideration is also given to direct environmental and safety risks and potential local commercial partners. The analysis shows that the solution is likely to be technically feasible, with potential markets in the livestock, field crop and horticulture sectors located in the provinces of the Northern Cape, Western Cape, North West, Free State, Limpopo and Mpumalanga. It was found that fewer than 13 commercial farms could likely be treated with the hypothetical sulfide-enriched coal waste produced in South Africa in a year. The transport costing analysis shows that the solution is likely to be uncompetitive with currently available soil ameliorants, but it may be competitive with waste disposal costs and augments resource effeciency. A research agenda for further development of the solution is put forth.