Chapter 12: Utilisation of Coal Combustion Products in Agriculture


Isa Yunusa, University of Technology Sydney, NSW
Veeragathipillai Manoharan, University of Technology Sydney, NSW & University of New England, Armidale, NSW
Margaret Burchett, University of Technology Sydney, NSW
Derek Eamus, University of Technology Sydney, NSW
Greg Skilbeck, University of Technology Sydney, NSW


As indicated in Chapters 1 and 2, coal combustion products (CCPs) include fly ash, bottom ash, boiler slag (furnace bottom ash) and flue gas desulfurisation material (FGD). The latter, however, is not produced by Australian coal-fired power stations. Fly ash represents the largest component of the group, accounting for up to 90% of the CCPs produced. The chemical composition of fly ash generally reflects the mineral matter of the parent coal, while the physical features (size and shape) of the particles often make it suited as an alternative material in applications that use sand, gravel or gypsum. Fly ash is made up of fine (1.0–100 µm), powdery particles, composed of crystalline minerals, amorphous aluminosilicates, and small proportions of unburnt carbon. The texture of fly ash is comparable to that of “silt and fine sand” soils (Adriano et al. 1980; Aitken et al. 1984; Palumbo et al. 2004). It is these general characteristics, both in terms of elemental composition and physical properties, which have generated increasing interest in fly ash as a viable product for soil management in crop and pasture production systems in Australia and in many other parts of the world.

Most agricultural soils have inherent structural and nutritional deficiencies that in many cases have been further exacerbated by modern farming systems. Farming involves frequent use of machinery, cultivation of exotic crops and trees, and application of synthetic fertilisers and pesticides. Modern agricultural practices have profoundly altered the structural and chemical characteristics of the soil, which in Australia is evident in the increasing acidity, salinity and sodicity (Rengasamy 2002; Yunusa & Newton 2003). Intensive and continuous cropping tends to mine the soil of nutrients through harvest and removal of plant materials.


  1. 12.1 Introduction
  2. 12.2 Benefits of Fly Ash in the Management of Australian Agricultural Soils
    1. 12.2.1 Mitigation of soil acidity
    2. 12.2.2 Amelioration of sodicity
    3. 12.2.3 Nutrient supply
    4. 12.2.4 Amelioration of soil structural and hydrological properties
  3. 12.3 Phytotoxic Considerations
  4. 12.4 Overall Benefit of Fly Ash to Plant Production
  5. 12.5 Choosing Fly Ash for Agricultural Soils
    1. 12.5.1 Salinity
    2. 12.5.2 Boron concentration
    3. 12.5.3 pH
  6. 12.6 Applying Fly Ash to Soil
  7. 12.7 Regulatory Imperatives
  8. 12.8 Other Considerations
    1. 12.8.1 Soil biota
    2. 12.8.2 Composting and/or blending of ash
    3. 12.8.3 Cost–benefit considerations
  9. 12.9 Emerging Issues and Opportunities
  10. 12.10 Concluding Remarks
  11. 12.11 References

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