Socio-ecological and economical impact of fly ash in soil reclamation

Application of fly ash for reclamation of soil is of much significance from the consideration of its disposal and gainful utilization. Based on intrinsic pozzolanic property and distinctive physico-chemical characteristics of fly ash/pond ash, lot of efforts has been made on this aspect globally. The characteristics of the ashes of significance include low bulk density, high water holding capacity and porosity, rich in silt-sized particles, alkaline nature, negligible solubility, reasonable plant nutrients. The studies made and conclusions drawn in mostly suffer from the variations of ash characteristics, soil types, and agro-climatic conditions. Finding out the relationship of the effects of ash between different plant species and soil types is difficult. The literature suggests huge potential for the bulk use of ashes alone and in combination with inorganic and organic amendments to improve cultivable, degraded/waste land, mine soil, landfills, and also to reclaim abandoned ash ponds through biological means. The toxicity concern generally is not of much concern owing to the ashes being generally alkaline, having elements of concerns in oxide form, and their concentration well below the limits prescribed for soil application of wastes. It may be of concern in respect of arsenic in he overseas ashes having higher range of arsenic than the prescribed limit. In Indian context, it is of least concern, particularly in view of overall minimum content of all the elements of concerns among the global ashes. Nevertheless, in case of any toxicity, there is plenty of scope for combating the problem through combination treatments particularly with organic materials and phytoremediation. The studies made in India using ash alone and in combination with other amendments on lab scale, pot experiment, research farm, and field scale, are in general promising. In particular, findings of demonstration trials including long-term field trials carried out at Central Institute of Mining & Fuel Research (Digwadih Campus) (erstwhile Central Fuel Research Institute), Dhanbad using the ashes alone and in combination with inorganic/organic amendment on cultivation of different pulses, cereals, oil yielding, and vegetable crops and growing various plant species in cultivable and problematic soils are encouraging in an eco-friendly manner, and being adopted by the farmers. The best ash application doses being up to 100 t/ha for cultivable land and up to/and or beyond 200 t/ha for waste/degraded land and mine refuse depending on their characteristics. Combination treatments including bio-solids are bette as compared with ash alone application. Such applications of fly ash with corresponding beneficial impact on agriculture and forestry could solve the disposal problem of gigantic ash generation in an eco-friendly manner and improve the socio-economic condition of the farmers. This, above and beyond, continuous study in parallel for longer duration, needs to be accelerated by the Government of India with renewed interest through different extension programmes involving the State Governments, farmers, and ash generating organizations to achieve maximum utilization.