While India has made tremendous advancements in establishing green power plants and increasing the utilisation of renewable energy sources, coal and lignite account for 73 per cent of the total electricity generated. Due to the low calorific value of Indian coal, the ash content accounts for 30-60 per cent. Utilising this ash is necessary in order to address the environmental issues associated with ash generation.
While fly ash utilisation levels have improved, they vary across power stations and remain relatively low for some thermal power plants (TPPs). As per the Central Electricity Authority (CEA) data, approximately 92 out of 200 power utilities have utilised over 100 per cent of fly ash by reusing the fly ash from the previous year. Overall, in 2021-22, approximately 259.86 million tonnes (mt) out of the 270.82 mt of fly ash generated by all TPPs (95.95 per cent) was utilised.
Recent policy developments
In 2021, the central government mandated that coal or lignite thermal power plants (TPPs) must ensure 100 per cent utilisation of ash generated during that year. It specified that under no circumstances should utilisation fall below 80 per cent in any year, and TPPs are required to achieve an average ash utilisation of 100 per cent in a three-year cycle. It gave TPPs a 10-year window to gradually utilise the accumulated unutilised ash (legacy ash).
Subsequently, a new notification was issued to clarify the compliance dates for the complete utilisation of fly ash for TPPs. It stated that the utilisation targets, as per the applicable compliance cycle, will be effective from April 1, 2022. The time for utilisation was extended to three years from one year, starting April 1, 2022. Further, areas where fly ash is stored can be reclaimed by setting up solar and wind power plants, along with plantations.
In June 2023, the CEA released guidelines on the design, construction, operations and maintenance and annual certification of coal ash ponds. The report encompassed aspects such as siting, location, planning, technical specifications, design, engineering standards, disposal system regulation and maintenance procedures. It also included annual certification to ensure the secure storage of ash and to meet the plant’s requirements and the standards set by the Ministry of Environment, Forest and Climate Change (MoEF&CC) for ash utilisation. Further, the report discusses the variables that have an impact on the environment, such as ash dike failure or breach, fugitive dust emissions, and contamination of groundwater and surface water bodies. To address these concerns, remedial measures have been suggested.
Further, to incentivise fly ash users and promote the utilisation of ash in construction and brick kilns, the central government provided 20 per cent of fly ash free of cost to small industries/users, while the remaining 80 per cent was sold through a tendering process. However, in June 2023, Maharashtra State Power Generation Company Limited decided to sell 100 per of cent fly ash, including both dry fly ash and pond ash, through the tendering process.
Trends in ash utilisation
According to the report released by the CEA on fly ash generation and utilisation for 2021-22, 92 out of 200 power utilities have achieved 100 per cent of ash utilisation during that period. More than half of the fly ash generated has been used in all states.
During 2021-22, 10 states — Andhra Pradesh, Bihar, Chhattisgarh, Madhya Pradesh, Maharashtra, Odisha, Tamil Nadu, Telangana, Uttar Pradesh, and West Bengal — produced over 10 mt of fly ash each. Chhattisgarh produced the highest amount at 44.9589 mt.
According to NTPC Limited, ash utilisation in 2021-22 increased to 80.94 per cent due to several reasons. This has primarily been driven by ash utilisation in activities such as cement manufacturing, road construction, mine filling and ash dyke raising.
Enormous volumes of ash produced by coal-fired TPPs can significantly enhance large-scale ash utilisation when transferred to remote areas where there is a greater demand for ash. Rail transport is a viable option for efficiently moving ash from power plants to distant demand centres. For instance, in the ongoing and future coal-fired projects by NTPC, the implementation of the ash rail loading system simplifies the rail transportation of fly ash.
Efforts are also being made to promote ash utilisation in ongoing road projects. The National Highways Authority of India (NHAI) is a major consumer, incorporating ash for landfill purposes in ramps and approach roads of the flyovers. As per estimates, the NHAI requires 95 million cubic tonnes of fly ash for its operations.
Meanwhile, ongoing efforts in the development of new products and methods for the usage of bulk ash have led to the creation and implementation of unique technologies and products such as geopolymeric concrete roads, geopolymeric pavers and tetrapod. In the past year, technologies such as piezoelectric-based sensors have been used to measure the ash level.
Another key development has been the export of fly ash. Recently, NTPC’s Simhadri plant exported 50,000 mt of fly ash to South Africa, marking the single largest consignment of fly ash exported from the country. Additionally, over 10,000 mt of fly ash was exported to Bangladesh. Further, negotiations are currently underway to explore the possibility of exporting fly ash to the Middle East and the United Arab Emirates.
NTPC is embracing the latest technology for thermal power generation and reducing water consumption in ash handling. For instance, for the ongoing coal-based thermal power project at Patratu, it has deployed a dry bottom ash handling system instead of the traditional wet bottom ash handling system. A dry bottom ash handling system eliminates the need for water usage during bottom ash handling, as the ash is extracted in a dry form with minimal water required for dust suppression and conditioning. This method not only reduces the water requirement for disposing of bottom ash in its wet form but also reduces power consumption, enabling greater utilisation of bottom ash. Another facility deployed in all NTPC stations is the ash water recirculation system, which treats wastewater and reuses the treated effluents. Dry bottom ash handling systems are implemented to reduce water consumption while disposing of coal ash, resulting in lower power consumption and improved utilisation.
The way forward
As a measure to streamline the fly ash monitoring process, in 2022, the National Green Tribunal (NGT) directed the central government to establish a fly ash management and utilisation mission to oversee the scientific management and utilisation of the ash from burned coal. The NGT further instructed the central government to take appropriate measures against power facilities that are not in compliance. The mission will also publish roadmaps and progress reports on fly ash utilisation available for all TPPs and their clusters on the MoEF&CC website, on a quarterly basis, to keep all the stakeholders informed.
To conclude, while ash management systems and utilisation have improved over the years, development has been slow. The government needs to incentivise firms to expedite their processes and should redirect its focus towards generating demand for ash utilisation. Additionally, stringent measures should be implemented to ensure compliance with regulations by the non-compliant power plants. Furthermore, the adoption of high concentration slurry disposal systems and dry bottom ash handling systems can improve efficiency and lead to a reduction in waste generation, offering financial advantages to operators. IoT-based ash management systems coupled with government initiatives can significantly improve ash utilisation.