In a bid to curb pollution levels in the country, the Ministry of Environment, Forest and Climate Change has notified revised emission standards for coal-based power plants, which are proposed to be implemented in a phased manner. The revised standards are aimed at reducing emissions of particulate matter (PM) to 0.98 kg per MWh, sulphur dioxide (SO2) to 7.3 kg per MWh and oxides of nitrogen (NOx) to 4.8 kg per MWh. The move is intended to bring about an improvement in the ambient air quality in and around thermal power plants (TPPs). In addition, the notification specifies the water consumption limits for TPPs.
The standards are based on the recommendations of the Central Pollution Control Board and consultations with stakeholders. The ministry had sought the views/comments of the general public in May 2015 and after detailed discussions, the standards were notified in the Gazette of India on December 7, 2015 through an amendment in the Environment Protection Rules, 1986.
New emission norms
For the purpose of formulating revised emission standards, TPPs have been classified into three categories — units installed before December 31, 2003; installed after 2003 till December 31, 2016; and installed after December 31, 2016. Different emission standards have been set for all three categories; however, TPPs that are set up from January 1, 2017 onwards will have to comply with the stringent emission norms.
For TPP units older than 2003, the norms will be relatively relaxed. The PM and NOx standards have been fixed at 100 milligram per normal cubic metre (mg per Nm3) and 600 mg per Nm3 respectively, irrespective of plant capacity. However, SO2 emission standards are different depending on the installed capacity. In the case of units with a capacity of 500 MW and above, the threshold limit has been fixed at 200 mg per Nm3 and for units with capacity less than 500 MW, the limit is 600 mg per Nm3.
In the second category, that is units installed after 2003 till December 31, 2016, the PM and NOx standards have been fixed at 50 mg per Nm3 and 300 mg per Nm3 respectively. The SO2 emission standards are similar to those applicable to TPP units established before December 31, 2003.
TPP units that will be established post January 1, 2017 will have to conform to PM standards of 30 mg per Nm3, and SO2 and NOx standards of 100 mg per Nm3 irrespective of the plant capacity.
With regard to mercury emissions, the threshold limit has been fixed at 0.03 mg per Nm3 for all three categories of TPPs. However, for plants installed before December 31, 2003, the revised norms will apply to only those units that have a capacity of 500 MW and above.
The emission standards have been significantly tightened. So far, PM standards for TPPs with power generation capacity of more than 210 MW were 150 mg per Nm3 and for plants with less than 210 MW capacity, they were set at 350 mg per Nm3. However, these PM standards are quite lax as compared to global norms. Moreover, standards pertaining to SO2, NOx and mercury emissions are completely absent. The existing TPPs are required to mandatorily comply with the new emission norms within a period of two years from the date of notification.
Water consumption limit
As per the new norms, all existing TPPs with a once-through cooling system need to install cooling towers (CTs) and achieve a specific water consumption of 3.5 m3 per MWh (maximum). The existing CT-based plants will have to reduce their specific water consumption up to a maximum 3.5 m3 per MWh. Similar to emission standards, the existing plants will have to comply with the water consumption limits within a period of two years from the date of notification.
However, the new units (commissioned from January 1, 2017 onwards) will have to restrict their specific water consumption to 2.5 m3 per MWh. In addition, these plants will be required to achieve zero liquid discharge.
The way ahead
In the wake of India’s commitment to reduce the emissions intensity of its GDP by 33-35 per cent from the 2005 levels by 2030, the notification of revised emission norms is a positive step. The new standards are expected to reduce PM emissions from new plants by 25 per cent; SO2 emissions by 90 per cent and NOx emissions by 70 per cent. Moreover, the technology deployed to control SO2 and NOx is expected to help reduce mercury emissions by 70-90 per cent. The new limits are also expected to lead to water conservation of 1.5 m3 per MWh. However, the key lies in strict enforcement, which calls for the strengthening of regulatory systems, implementation of advanced pollution monitoring technologies, development of clean coal technologies and stringent penalties for violations.