Fly Ash Dykes

ENERGY & ENVIRONMENT

Reclamation of fly ash dykes Out of the ashes This may literally read like a leaf from the Egyptian mythology—Phoenix rising from the ashes, after being completely consumed by fire. For this is an equally enduring effort to sow seeds of life on heaps of dead, dry, and toxic ashes—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 Vijaywada (Andhra Pradesh) stand testimony to this technological marvel.

Fire beneath ash When coal 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. So, when your lungs start turning blue, your eyes red, or your skin purple, it could be that coal is burning persistently in the nearby power plant. However, at the emission point, fly ash is captured using electrostatic precipitators and dumped as slurry in ash dykes. There again, as the toxic metals seep into the ground, or fly with wind, they severely contaminates 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 any use.

A new lease of life While power stations are clueless about how to minimize the fly ash hazards, researchers at T E R I come up with a technological innovation, resurrecting hope. The technology was first demonstrated at the Badarpur Thermal Power Station and the Korba Super Thermal Power Station by turning their fly ash dump yards into stretches of green cover (Figure 1). The technology gained multiplier effect at the Korba State Thermal Power Station (another power-generating unit at Korba) and the Vijayawada Thermal Power Station. 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

Figure 1 A fly ash dyke at Korba Super Thermal Power Station, Chattisgarh, before the technology demonstration by TERI. Inset: The same site after intervention

14

TERI’S technologies for sustainable development

Fugitive dust in un-reclaim ed surroundings

Tech no lo gi ca

l so lu tio ns

Thoughtful intervention

Figure 2 A fly ash dyke in Korba showing both un-reclaimed surroundings and technological solution

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 (Figure 3).

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 find out their growth pattern on fly ash dumps. Strains offering high tolerance, assisting in survival, and providing 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. And, when put to application, 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.

Plants to be grown on fly ash dumps were carefully selected. Bearing in mind that the toxicity and stressful elements in plant species grown on fly ash are yet to be established, only those species were chosen that are not part of the food chain, but have commercial value—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).

Applications/benefits The reclamation technology based on mycorrhiza organobiofertilizer is promising enough to metamorphose the 30 000-odd hectares of fly ash dumps in India into a huge commercial proposition (Box 1).

Bo Boxx 1 Making sense of a choice The reclamation technology based on mycorrhiza organo-biofertilizer, developed by TERI researchers, offers to play a value-adding, multifarious role. The technology P involves no good earth application; P requires no chemical fertilizer; P reduces fugitive dust emission in power plants; P checks groundwater contamination; P offers multiple ways for economic gains; and P enables bio-diesel plants to grow on ashes, which, that, apart from being commercially viable, supplements energy inputs in power plants.

Figure 3 Mycorrhized Jatropha produces early and high yield on ash dykes

To reclaim one hectare of fly ash dump, using TERI technology, costs 90 000 rupees. This includes the cost of field preparation, nursery raising, mycorrhiza inoculation, irrigation, plantation, grass bed preparation (with Jatropha and vetiver for revenue generation), and maintenance up to one year. Many entrepreneurs have already shown great interests in setting up floriculture and silviculture projects on fly ash.

15