Large-scale use of fly ash can increase agricultural output by 10%
Dr Vimal Kumar is Secretary General, C-FARM, an entity devoted to scientific and techno-managerial guidance and consultancy for adaptation of fly ash utilisation. He speaks on the latest developments on this front.
What is C-FARM? How have you been helping C-FARM meet its objectives?
C-FARM was established during 2007 at the instance of the Department of Science & Technology (DST), Government of India. I was then the Head, Fly Ash Unit (FAU), DST. There was a large demand from industry for scientific and techno-managerial guidance/ consultancy for adaptation of fly ash utilisation, safe management technologies and related aspects. The then Secretary, DST suggested that this demand of industry can be best met through a Section (25) company spearheaded by eminent fly ash experts. Since then, I have been associated with C-FARM for sharing experience and expertise as well as providing guidance and assistance to engineers, scientists, staff and panel experts of C-FARM to meet the objectives and purpose of C-FARM. I was initially working as Honorary Adviser with permission of the Government of India till superannuation in June 2013. Thereafter my association with C-FARM continued on the same basis till July 2014 when the Board of Directors of C-FARM designated me as Secretary General.
While generating power, we get fly ash as a by-product, but we also get bottom ash and pond ash. How can these other two ash products be used?
Based on point of collection, various parts of fly ash are given different names. The fine ashes collected from flue gases at the Electro Static Precipitator (ESP) or filter bags or any such mechanism is called ESP ash. The coarser ash that falls at the bottom of the boiler and is collected separately is known as bottom ash. At a few power plants, the bottom ash is being conveyed and stored in a separately earmarked area. In most of the power plants, it is mixed with unutilised ESP ash and is stored either in lagoons, known as ash ponds or in the form of a mound, known as mound ash.
All categories of fly ash, i.e., ESP ash, bottom ash, pond ash or mound ash are useful materials. None of them is waste material.
Each of these fly ash categories can be used for other application areas with appropriate design and methodology, if necessary.
Apart from the use of fly ash in making cement, bricks and concrete, what are the other uses of fly ash, particularly in the field of agriculture?
The other uses of fly ash, other than for cement, concrete and construction activities are many, like reclamation of low-lying areas, mine-filling, agriculture, forestry, waste-land development, part-replacement of gypsum in agriculture, value-added products and use as a effluent treatment agent, etc.
Use of fly ash in agriculture
By virtue of its physical properties, fly ash improves soil textural properties and soil aeration; improves water-holding capacity/porosity and reduces bulk density and crust formation.
Due to its chemical constituents, fly ash provides several micronutrients such as Mo, B, Mn, Fe, Zn, Cu, etc.
It is also the source of many macronutrients like Mg, S, K, P, Ca, etc.
It can also be used as an alternative for gypsum for reclamation of sodic soils and lime for reclamation of acidic soils.
Use of fly ash in agriculture has shown to increase the yield of cereals, oil seeds, pulses, cotton and sugarcane.
Detailed study of radio nuclides and heavy metals content in fly ashes and their impact on agriculture use has been undertaken at the Institute of Physics (IOP), Bhubaneswar, a constituent laboratory of the Department of Atomic Energy, Government of India. The study concludes that the levels of radio nuclides and heavy metal content in fly ashes, fly ash admixed soil and crop produce are within the safe/normal range.
The impact of fly ash/pond ash on toxicology and nutritional quality of crop produce has been studied for two years over a range of crops at NIN, Hyderabad, a constituent laboratory of the Indian Council for Medical Research (ICMR), Government of India. NIN has reported that there is neither any harmful impact of heavy metals nor any change in proximate composition and trace mineral content in crop samples grown with fly ash/pond ash.
In conclusion, it can be said that use of fly ash in agriculture as an ameliorant holds the potential to improve the soil health of fields under cultivation as well as that of degraded/ problematic soils. The large scale use of fly ash in agriculture can increase the agriculture output of the country at least by 10 per cent, contributing immensely to food security objectives.
In the present scenario, only around 50-60 per cent of fly ash is usefully consumed. How can this situation improve?
The majority of unutilised fly ash is at the power plants that are in a cluster, generally located at coal mine pit heads. At these locations, the avenues for use of fly ash in building construction, infrastructure development, manufacture of cement, concrete, etc., are very limited. On the other hand, generation of fly ash is much larger due to concentration of power plants.
The solution lies in putting in practice the demonstrated and developed applications of fly ash for filling of mines, reclamation of low-lying areas/ravines, use in agriculture, forestry and waste land development, etc. These applications hold the potential to consume all the fly ash that is being generated at such locations.
Initiatives from thermal power plant agencies, required encouragement/support from statutory bodies and willing partnership of owners of perspective fly ash user properties can bring in the desired results.
The fly ash notifications of the Ministry of Environment, Forest and Climate Change (MoEF & CC) of 1999, 2003, 2009 and 2016 mandate the above said uses of fly ash. Implementation needs to be ensured.
Tell us something more on beneficiation and segregation of fly ash for value addition...
Segregation and value addition to fly ash is end-application oriented. Value addition can be done mechanically or chemically or even metallurgically in addition to the simplest methods of segregation and classification. The selection of process is governed by the hierarchy of the end value-added application.
West Bengal and Maharashtra have been exploring the possibility of exporting fly ash. What is the potential for fly ash exports?
Indian fly ash has a good potential for exports, not only to nearby overseas markets, but also to Europe and the USA. India is already exporting large volumes of fly ash to Bangladesh, Sri Lanka, Kenya, Oman, Qatar, UAE, etc. Recently, queries have been received from Europe and USA due to the shift from coal-based power plants in these regions, and due to Indian fly ash being of a better quality in terms of low un-burnt carbon and fineness. A great potential exists for exports. The infrastructure facilities at Indian ports need augmentation.
How about using the part of bottom ash as aggregates for concrete - what has been the work done so far and where can it be taken further?
Bottom ash is granular material like fine sand. Its use has been developed and established as a part substitution for fine aggregate, i.e., sand. The latest amendment to IS: 383, specification for coarse and fine aggregates, has also permitted part substitution of sand by coarser fly ash i.e., bottom ash.