EN10 Residues from combustion of coal for energy production

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Residues from coal combustion provide an indication of the quality of the coal used for power generation and of the use of pollution abatement technologies. The environmental impact caused by the handling of residues can be low if residues are utilised or disposed of in an environmentally safe way, but unsafe utilisation, storage or disposal has risks of local water pollution.

Residues from coal combustion in the EU-15 were stable in the 1990s and increased since then to amount to about 59 million tonnes annually (Brennan et al., 2003) and approximately 65 million tonnes in the 10 new EU Member States (ca. 30 million tones) and other European Countries (ca. 35 million tonnes). These amounts represent about 3.6 % and 4 % respectively of the total generation of waste and residues from all economic activities in the EU-15 and EU10.

The amount of solid residues generated by fossil fuel combustion depends on the content of non-combustible substances in the fuel, i.e. ashes, and sulphur. The main coal combustion residues are fly and bottom ash, boiler slag and fluidised bed combustion ash. In addition, the environmentally motivated removal of SO2 through flue gas desulphurisation or spray dry absorption generates solid sulphur residues such as gypsum (see Figure 5 in the data annex).

The trend towards a rising amount of sulphur residues reflects the steady increase in the number of flue gas desulphurisation units used to control SO2 emissions. There was a declining trend in ash generation during the 1990s and a re-increase from 1999 onwards. The decline in the 90s can partially be explained by a reduction in the use of coal as fuel in this period, combined with a switch towards the use of coal of higher quality, with lower ash content (Brennan et al, 2003). The increase by the turn of the century indicates a return to the use of coal as fuel.

Future generation of coal combustion residues is difficult to predict, because generation is affected by several factors of opposite sign. On the one hand, the progressive installation of air pollution control equipment in power plants, avoiding gas and particle release to the atmosphere, can result in increasing amounts of residues being generated in the coming years. On the other hand, a EN10-Residues from coal combustion possible reduction in the use of coal for power generation and a switch to low-ash and low-sulphur containing coal can result in an overall decrease of residue generation.

Within the EU-25, five countries (Germany, Greece, Spain, Poland, and the UK) account for about 80% of the total generation of residues. Differences between countries are to a large extent due to different amounts of coal consumption, but also to differences in the efforts made in installing flue gas cleaning technologies.

Most residues from coal combustion are not hazardous and, if well managed, can be used as by-products or as filling material, mainly in the construction industry. In the EU-15, almost all gypsum from flue gas desulphurisation and all boiler slag are used, mainly as construction materials. Ash is used as construction material but also as filling material in open cast mines, quarries and pits. Utilisation of fly and bottom ash increased by around 10 percentage points between 1993 and 2001 to reach 46% and 41% respectively (ECOBA, 2003).