India has enough limestone to help coal-based thermal power plants meet the new emission norms, says CSE’s new report

Study on flue gas desulphurization (FGD) systems refutes thermal power industry’s contention that the country does not have enough limestone 

  • Limestone is needed for operating flue gas desulphurization (FGD) systems in thermal power plants. FGD systems help control emissions of sulphur dioxide (SO2) from these plants. Coal-based thermal power plants have to meet new emission norms by 2022. 
  • India is the largest emitter of SO2 in the world. Thermal power plants account for 45 per cent of total industrial emissions of SO2 in the country. FGD systems in thermal power plants can reduce SO2 emissions from them by 80 per cent. 
  • FGD gypsum, the by-product in the FGD process, can help India meet some of the shortfall in its output of gypsum. 
  • Report recommends setting up guidelines on handling, storage, transportation, quality control etc of limestone and gypsum. It also offers suggestions on use of FGD gypsum in sectors such as cement production and high end gypsum products like wall boards and plaster boards. 

New Delhi, March 31, 2020: India has enough reserves of limestone to enable thermal power plants to install flue gas desulphurization (FGD) systems by 2022 in order to meet the new emission norms for the sector, says a new report released online here by Centre for Science and Environment (CSE). This refutes the contention of power plants, which have been trying to delay implementation of the norms by -- among other things -- raising concerns about availability of limestone and use of its byproduct, FGD gypsum.  

To meet India’s new emission norms by 2022, a large number of coal-based thermal power plants have to install FGD systems. Limestone is a key raw material in most FGD systems for controlling sulphur dioxide (SO2) emissions. Flue gas desulphurization – limestone availability and gypsum use, as the CSE report is titled, attempts to examine the issue of availability of limestone for FGD. 

Said Sunita Narain, director general, CSE: “Many thermal power companies have been raising various concerns regarding FGD installation; one of these is about the availability of limestone, and the use or disposal of FGD gypsum, a by-product of the FGD operation. This report attempts to address both these key issues.” 

Say CSE researchers behind the report: “The coal-based power sector would require only seven to 10 million tonnes of limestone annually for operating FGD systems. This is less than 3 per cent of India’s present limestone consumption. For use in FGD, high-quality limestone (CaCO3 > 90 per cent) with minimal impurities is desirable. Industry experts believe that producing additional high-quality limestone would not be a challenge given our large reserves. Moreover, regional distribution of limestone reserves shows that access will not be a problem as a majority of power plants are located within 200 km of a limestone mine.”  

Gypsum is a scarce resource in India. The quality of FGD gypsum is at par or even better than mineral gypsum and it has become a substitute for mineral gypsum across the world. China is able to utilise more than 70 per cent of its FGD gypsum, largely in cement and construction. In India as well, gypsum is an integral component of cement production and the sector has to rely on costly imports or poor-quality synthetic gypsum. CSE estimates that by adopting FGD, India’s power plants would produce around 12-17 million tonnes of gypsum which can easily meet the domestic shortfall and reduce the import burden. The cost of limestone, says CSE, will not be significant as it can be offset by selling FGD gypsum. 

Key recommendations

  • To ensure safety and minimise fugitive emissions, the Ministry of Environment, Forest and Climate Change (MoEF&CC) should release guidelines for ensuring appropriate safeguards in handling, storage, and transport of limestone and gypsum. 
  • The Bureau of Indian Standards (BIS) has specified broad guidelines for gypsum being used in the cement sector. The BIS may also need to specify the quality of limestone being used in FGDs to ensure good quality FGD gypsum. 
  • While the use of FGD gypsum in the cement industry should be encouraged, it is also necessary to provide incentives to the manufacturers of high-end gypsum products like wall boards and plasterboards. 
  • The agriculture sector can also become a valuable consumer of FGD gypsum; however, certain quality checks and field trials are essential to ensure that its use in agriculture is safe. 
  • In the long term, power plants should be directed to use all the FGD gypsum that is produced; however, the short-term disposal guidelines can be issued.  

Said Narain: “India is the largest emitter of SO2 in the world, contributing more than 15 per cent of global anthropogenic emissions. FGD systems in thermal power plants can reduce SO2 emissions from them by 80 per cent, points out this CSE report.” 

For more on this or for interviews etc, please contact Sukanya Nair of The CSE Media Resource Centre,, 88168 18864. 

To access the CSE report: