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While mining and coal burning have received their fair share of attention, the dangers of coal ash and the impacts of its disposal are still under the radar. Between 2010 and June 2020, several ash pond accidents have been reported across India. These accidents have caused deaths, extensive pollution of the water, air, soil, and loss of property. Unfortunately, the public outrage associated with coal ash pollution remains limited to big disasters. The slow poisoning of communities living around ash containment ponds goes unnoticed. Indian coal fired thermal power plants generate an average of 200 million metric tons of ash annually and this has been steadily increasing every year. This figure is expected to cross 300 mn by 2032 . As per the current estimates of the Central Electricity Authority, Indian power plants generated 217.04 million metric tons of ash in the year 2018 [based on data received from 195 thermal power stations].
Apart from being a management challenge for plant operators, such vast quantities of ash itself poses several public health challenges for communities living around the ash disposal sites. Just in terms of land use -- the conventional disposal of ash in the form of slurry currently occupies nearly 40,000 hectares of land and requires about 1040 mn m3 of water annually.
Indian power plants primarily burn varieties of bituminous coal which is destined to generate more ash. On average, Indian coal generates anywhere between 30%-45% ash [after coal washing] which translates to roughly 1.8 MTDA for a 1000MW plant.
Types of Coal Fly Ash:
A typical power plant generates mainly two types of ash, a fly ash and bottom ash. Fly ash is captured by automatic or electrostatic precipitators before the gases exit the stack; the bottom ash deposits at the lowermost section of the boiler. Approximately 20% of total ash generated in a power plant is delivered as bottom ash. In practice, the power plants use water to flush the rejected or excess unutilized fly and bottom ash together into large holding ponds or dykes, this is referred to as ‘pond ash’. When the same ash is dumped without water it is referred to as 'mound ash'.All fly ash contains substantial amount of silica and calcium oxide or lime that render it the pozzolanic properties. Fly ash for concrete is classified into Class C and Class F depending on the calcium, alumina, silica and iron content. While the former has enough calcium to exhibit cementitious properties to be used as cement by itself, the latter is typically used to partially replace Portland cement in the manufacturing process. Indian power plants primarily generate Class fly ash. Effectively, only fly ash [in its pure form, without mixing with bottom ash] is desirable for cement manufacturing.
Coal Ash Toxicity:
Trace amounts of toxic heavy metals and other chemicals are naturally infused into the mined coal. These substances are liberated when coal is burnt and ultimately concentrate either into the bottom ash or the fly ash. Evolving pollution control technologies capture even more of these toxins from the smokestacks and further concentrate them into the fly ash. Typically, coal ash consists of arsenic, lead, mercury, selenium, hexavalent chromium among other carcinogens and neurotoxins.
Historically, generating coal fly ash and managing of it have been seen as a challenge to policy makers, regulators and engineers. Generally two approaches have been adopted to get round to this problem:
[i]. limiting fly ash generation by improving the quality of coal in power plant [washing selecting low ash content coal etc.,]
[ii]. Enhancing fly ash utilization through relevant policies.
The aim of the notification was to achieve a reduction in the ash content down to 34% by 2016 for power plants located at distance of more than 500 Kms from the pithead, or those near urban areas, and those near sensitive or critically polluted areas. However, on 21st May 2020, the Ministry of Environment Forest and Climate Change [MoEFCC] made coal washing optional through a controversial amendment based on economic rationale offered by India‘s NITI Aayog. Unfortunately, this rationale does not account for the resulting increase in the fly ash generation and pollution caused from it.
The aim of the original notification and subsequent amendments and the Fly Ash Mission launched in 1994 has been to achieve 100% utilisation of fly ash within a specified period. Despite these efforts only 77% of the fly ash however has been utilised as of 2018-19. It is important to note here that "utilisation" is a misnomer for some of the "uses“ like filling of low-lying area reclamation and mine void filling are actually means of disposal. Despite government approval, certain uses of fly ash like mine void filling, low lying area reclamation and agricultural use were prohibited under the Environment Clearance [EC] conditions for power plants.
The latest amendment of August 2019 reverses such EC conditions.
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[i]. limiting fly ash generation by improving the quality of coal in power plant [washing selecting low ash content coal etc.,]
[ii]. Enhancing fly ash utilization through relevant policies.
Limiting Fly Ash Generation:
In order to reduce the ash content, the washing of coal has been made mandatory in India since 1997 and notifications to this effect were passed in 1997, 1998 and 1999, mandating coal washing. Subsequently the government issued a gazette notification on 2nd January 2014 making coal washing mandatory for supply to all thermal units more than 500 km from the coal mine.The aim of the notification was to achieve a reduction in the ash content down to 34% by 2016 for power plants located at distance of more than 500 Kms from the pithead, or those near urban areas, and those near sensitive or critically polluted areas. However, on 21st May 2020, the Ministry of Environment Forest and Climate Change [MoEFCC] made coal washing optional through a controversial amendment based on economic rationale offered by India‘s NITI Aayog. Unfortunately, this rationale does not account for the resulting increase in the fly ash generation and pollution caused from it.
Enhancing Fly Ash Utilisation:
In order to reduce the volume of ash, MoEFCC has focused on enhancing the utilisation of fly ash through notifications, first brought on 14th September 1999, and subsequently amended in 2003, 2009, 2016 and 2019. The latest amendment vide an Office Memorandum was announced on 28th August, 2019. The 1999 Fly Ash notification mandates the utilisation of fly ash for cement, concrete blocks, bricks, panels and similar materials or for the construction of roads, embankments, dams or for any other construction activities within a radius of 300 km from thermal power stations [TDDs].The aim of the original notification and subsequent amendments and the Fly Ash Mission launched in 1994 has been to achieve 100% utilisation of fly ash within a specified period. Despite these efforts only 77% of the fly ash however has been utilised as of 2018-19. It is important to note here that "utilisation" is a misnomer for some of the "uses“ like filling of low-lying area reclamation and mine void filling are actually means of disposal. Despite government approval, certain uses of fly ash like mine void filling, low lying area reclamation and agricultural use were prohibited under the Environment Clearance [EC] conditions for power plants.
The latest amendment of August 2019 reverses such EC conditions.
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Click here for full report
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