Reclamation of fly ash dykes
Out of the ashes
This may read literally like a leaf from Egyptian mythology-Phoenix rising from the ashes, after being completely consumed by fire. For it is an equally enduring effort to sow seeds of life on heaps of dead, dry, and toxic ash-dykes of fly ashes resulting from coal-fired power generation plants. Using mycorrhizal technology, TERI researchers have found ways to reclaim fly ash dumps. The lush green expanses surrounding the power plants at Badarpur (Delhi), Korba (Chhattisgarh), and Vijayawada (Andhra Pradesh) stand testimony to this technological marvel.
Fire beneath ash
Indian cola has very high ash content. When it burns, it produces fly ash-fine
solid particles of ash, dust, and soot containing lead, arsenic, cadmium, cobalt,
silica, mercury, and other toxic elements. It becomes a deadly source of health
hazards when carried into the atmosphere. However, at the emission point, fly
ash is captured using electrostatic precipitators and dumped as slurry in ash
dykes. As particles of toxic metals seep into the ground, or fly with wind,
they severely contaminate groundwater, lower soil fertility, harm aquatic plants,
and disturb the food chain. With about 70 thermal power plants in India - and
there are plenty more in the offing - fly ash dykes have claimed nearly 30 000
hectares, turning them unfit for use.
A new lease of life
While power stations are clueless about how to minimize the fly ash hazards,
researchers at TERI have come up with a technological innovation, thereby resurrecting
hope. The technology was first demonstrated at the Badarpur Thermal Power Station
and the Korba Super Thermal Power Station. It turned their fly ash dump yards
into stretches of green cover. The technology gained multiplier effect at another
power-generating unit: the Korba State Thermal Power Station and the Vijayawada
Thermal Power Station.
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| A fly ash dyke at Korba Super Thermal Power Station, Chhattisgarh, before the technology demonstration by TERI. Inset: the same site after intervention |
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| A fly ash dyke, post reclamation |
The process works with the help of naturally occurring mycorrhizal fungi that, through their mycelial network, accumulate heavy metals from fly ash and retain them within their cells or carry them on the body surface. These mycelial threads, along with dense root biomass, assist in ash-particle binding. Mycorrhizal fungi form a reciprocating relationship with the living roots of higher plants-they provide nutrition to plants and, in turn, receive carbon from them. The mycorrhizal association, with small quantities of compost added, benefits plants tremendously in terms of their growth rate, tolerance to biological and environmental stresses, and seedling survival.
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| A fly ash dyke in Korba showing both unreclaimed surroundings and technological solution |
A crusading act
Different strains of mycorrhizal fungi were collected from diverse regions of
India and abroad. These were then isolated, selected, multiplied, and tested
under greenhouse/nursery conditions to know their growth pattern on fly ash
dumps. Strains that offer high tolerance, assist in survival, and provide nutritional
support to plants were selected for the purpose. With additional doses of organic
and mycorrhizal fertilizer to optimize the impact, the mycorrhizal strains were
then applied to the plants on fly ash dumps. In some time, life sprouted on
grey, degraded, toxic wastelands in the form of green vegetation. Having implemented
the technology successfully, TERI researchers are now heading for several multi-location
demonstrations.
Thoughtful
intervention
Plants to be grown on fly ash dumps were carefully selected. Since the toxicity
and stressful elements in plant species grown on fly ash were yet to be established,
only those species that were not part of the food chain, but had commercial
value were chosen such as tree species for timber (poplar, sheesham, eucalyptus,
meethi neem, and the like); floriculture and aromatic species (marigold, sunflower,
lemongrass, tuberose, gladiolus, lily, and the like); and species for biofuels
(Jatropha and vetiver). Many entrepreneurs have already shown great interest
in setting up floriculture and silviculture projects on fly ash.
Applications/benefits The reclamation technology based on mycrrhiza organo-biofertilizer,
developed by TERI researchers, offers to play a value-adding, and
multifarious role. The technology The cost of preparing a nursery on an acre of land, for
example, amounts to 31 600 rupees whereas with the traditional method, it could
cost 24 500 rupees. The per acre plantation cost for TERI's technology is 81 100
rupees, as compared to 84 400 rupees for traditional technology. Though how environmental
benefits translate into monetary gains has not yet been analysed, revenue generation
per acre in case of TERI's technology is 12 000 rupees as compared to 7 000 rupees
in case of conventional technology.
The reclamation technology based on the mycorrhiza biofertilizer is promising
enough to metamorphose the 30 000-odd hectares of fly ash dumps in India
into a huge commercial proposition.
Making sense of a choice
involves no good
earth application;
requires no chemical
fertilizer;
reduces fugitive
dust emission in power plants;
checks groundwater
contamination;
offers multiple
ways for economic gains; and
enables bio-diesel
plants to grow on ashes, which, apart from being commercially viable,
supplements energy inputs in power plants.