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Land Uses of Coal Fly Ash - Benefits and Barriers

AUTHOR: Irene Smith
DATE: May 2005

This report focuses on three major sectors of fly ash utilisation: soil stabilisation, mine backfill and agriculture. Requirements are generally less rigorous than for use of fly ash in the cement and concrete industries. The benefits of using fly ash are investigated for each sector. These include improvements over use of cement or lime alone at lower cost, more effective land reclamation using less primary materials, and enhanced fertility of soils.

Stabilisation of soils and aggregates with fly ash is a successful, high volume use, especially in road construction. Unbound fly ash as structural fill, for example in mines and road subbase, gives high volume, beneficial use of conditioned, stockpiled and lagoon fly ash. In agriculture, studies have shown that crop yields increase and water consumption may be reduced by using fly ash as soil amendment.

Fly ash is complemented well by biosolids such as treated sewage sludge and acts synergistically with organic matter in mproving plant growth. Barriers to utilisation of coal fly ash on land occur in marketing, transport, and through the potential for leachates containing trace elements from fly ash. These are being overcome by various means in the utilisation sectors. It is essential to follow best engineering practices to ensure there is no environmental risk. Potential long-term effects in agriculture are under investigation.