Coal waste management practices in the USA: an overview
International Journal of Coal Science & Technology
This paper provides an overview of coal waste management practices with two case studies and an estimate of management cost in 2010 US dollars. Processing of as-mined coal typically results in considerable amount of coarse and fine coal processing wastes because of in-seam and out-of-seam dilution mining. Processing plant clean coal recovery values run typically 50 %-80 %. Trace metals and sulfur may be present in waste materials that may result in leachate water with corrosive characteristics.
... ve characteristics. Water discharges may require special measures such as liner and collection systems, and treatment to neutralize acid drainage and/or water quality for trace elements. The potential for variations in coal waste production and quality depends upon mining or processing, plus the long-term methods of waste placement. The changes in waste generation rates and engineering properties of the coal waste during the life of the facility must be considered. Safe, economical and environmentally acceptable management of coal waste involves consideration of geology, soil and rock mechanics, hydrology, hydraulics, geochemistry, soil science, agronomy and environmental sciences. These support all aspects of the regulatory environment including the design and construction of earth and rock embankments and dams, as well as a wide variety of waste disposal structures. Development of impoundments is critical and require considerations of typical water-impounding dams and additional requirements of coal waste disposal impoundments. The primary purpose of a coal waste disposal facility is to dispose of unusable waste materials from mining. However, at some sites coal waste impoundments serve to provide water storage capacity for processing and flood attenuation. Keywords Coal waste Á Coarse coal processing waste Á Fine coal processing waste Á Coal refuse Á Out-of-seam dilution Á Dilution impacts Á Environmental impacts Á Reclamations 1 Coal waste management issues in USA Introduction Since the increased mechanization of surface and underground coal mining, the proportion of out-of-seam dilution (OSD) mining from immediate roof and floor strata and generation of more fines in the mined product has increased. The focus has been on improving productivity with higher advance rates with increasingly larger equipment without attention to OSD or product size. The recent decline in coal production in the US (Fig. 1) will in the near term reduce innovation as the industry will avoid risk. Due to this decline, the average production per employee hour actually decreased by 0.2 % in 2012 (EIA 2013) reversing a long-term trend toward improved productivity. In addition there has been an increase in public attention on the safety and environmental impacts of surface and underground coal mining that is affecting recent trends in coal waste management.