Technical Market Support » Thermal Coal
Trace elements in coal are receiving greater attention in the assessment of the environmental impact of electricity generation from coal-fired power stations. The levels of many trace elements of environmental concern are now assuming greater importance in terms of emission of air toxics, waste ash disposal strategies and ash utilisation processes. Australia is the world's largest exporter of thermal coal with 25.9% of the market. It is however facing increased competition from both traditional and new suppliers. With the increasing concerns about trace elements in coal utilisation it would be advantageous to demonstrate the environmental acceptability of our coals. This can be achieved by establishing a database on the levels of trace elements in thermal coals exported by Australia and those produced by its competitors for the international market.
The levels of trace elements in thermal coals are becoming of increasing importance in the assessment of environmental impact of electricity generation from coal-fired power stations. The concerns about trace element levels relate to the emission of air toxics and the disposal and utilisation of waste ash.
Recent amendments to the US Clean Air Act have classified a number of key environmental trace elements and imposed emission limits on their discharge limits. In many other countries legislation has been introduced limiting the discharge of environmental trace elements (Clarke and Sloss, 1992). In addition, regulations of ash disposal in a number of European countries have drawn attention to trace elements levels in waste ash and their potential environmental impact.
The stability of waste ash in ash utilisation processes such as the manufacture of building materials is also of concern, not only from the magnitude of the levels of trace elements present, but also from the radioactivity of the ash resulting from the presence of uranium and thorium and the natural radionuclides arising from their radioactive daughter products.
These concerns will focus more attention on the levels of trace elements in power station feedstocks and are likely to have a significant impact on the world thermal coal export market.
In order to maintain Australia's position as the major supplier of internationally traced coals, data on the levels of trace elements of environmental concern are required to demonstrate the quality and acceptability of Australian thermal coals in relation to environmental impact.
Previous data by Knott and Warbrooke (1984) and Dale et al. (1991), have shown that Australian thermal coals contain low levels of environmentally sensitive trace elements compared to overseas coals. However data available in the literature on the levels of trace elements in thermal coals produced by Australia's major competitors is rather sparse and of questionable value.
This is because of the lack of reliable and accurate standard methods of analysis and the uncertainties of the origin and representative nature of the samples for which data are presented.
The only valid comparison of the levels of trace elements in Australian export thermal coals and those supplied to the international market by its competitors would be to characterise representative samples of local and foreign coals in the one laboratory using reliable and validated analytical methods.
This has been achieved through the acquisition of a range of representative internationally-traded coals obtained through a European importer of power station feedstocks and the application of accurate and reliable analytical methods, based on modern techniques, developed in a current ACARP research project (Project No. C3015). For the comparison, a selection of Australian export thermal coals from New South Wales and Queensland were selected as being commonly supplied to the international market by Australia's major producers.
The coals were chemically analysed for most trace elements of environmental concern classified by the United States National Research Council (1980), and included the radioactive elements uranium and thorium as well as natural radionuclides arising from the radioactive decay of uranium and thorium isotopes.
Objectives of The Study
The aim of this study was to characterise a range of Australian export thermal coals and other internationally traded thermal coals for trace elements of environmental concern. To achieve this, representative export coals from the United States of America, South Africa, Indonesia, China, Poland, Colombia and Venezuela were obtained.
Both the Australian and international coals were analysed for key environmental trace elements using accurate and reliable methods developed in tis laboratory. These data would therefore provide a useful database to assist in marketing.
Australian thermal coals were found to generally contain significantly lower levels of arsenic, selenium and mercury. The levels of other trace elements of environmental concern differed both within and between the Australian and international coals. The significance of these differences can only be assessed in terms of the ultimate residence of the trace elements in waste products.
The potential environmental impact of the utilisation of the coals was assessed using a ranking procedure based on the combined effect of the most environmentally significant trace elements. Most Australian coals rated highly in terms of minimal environmental impact.
This study has provided the most reliable database yet available on the levels of trace elements of environmental concern in representative Australian and internally traded thermal coals.