CSE disputes CEA’s study urging relaxation of SO2 norms for thermal plants

New Delhi-based non-profit Centre for Science and Environment (CSE) has disputed the findings of a recent study by the Central Electricity Authority (CEA) on sulphur dioxide (SO2) norms, calling it ‘incomplete’ and ‘invalid’.

The study had called for the relaxation of SO2 norms for most coal-based thermal power stations (TPP) in India. The study report was prepared by CEA in response to discussions held with Union Minister for Power RK Singh on January 21, 2020.

Singh was reviewing the progress of installation of flue-gas desulphurisation technology (FGD) in TPPs. FGDs are used to reduce SO2 emissions from coal-based thermal power stations. The stations are needed to meet environmental norms by 2022.

Singh asked the CEA to produce a paper that could be used by his ministry to negotiate with the Union Ministry of Environment, Forest and Climate Change (MoEF&CC) to relax SO2 for power plants.

The CEA collected ambient air quality data from power plants of 35,708 megawatt (MW) capacity. It then categorised plants based on this data.

When it finally submitted the report in October to the power ministry, the body urged that FGDs be installed only in those plants where SO2 concentration in ambient air was over 40 microgram per Normal cubic metre (µg / Nm³⁾.

The CEA report overlooked various aspects including:

• Secondary conversion of SO2 to sulphates in particulate matter (PM 2.5 / 10)
• Impact of the dust plume over long distances of up to 300 kilometres
• Ambient SO2 levels in various cities other than where power stations are located

The document also misinterpreted the National Ambient Air Quality Standard to justify unabated emissions from power stations while neglecting various research studies on harmful effects of sulphur dioxide.

“CEA has extensively analysed the data. However, it has failed to explain where the SO2 from thermal power plants goes. A complete life-cycle analysis is missing,” a retired official from the Central Pollution Control Board told Down To Earth on the condition of anonymity.

“Low levels of SO2 in the ambient air can be deceptive as they may be adding to the very serious problem of sulphate particulates, which are deadlier than PM10 or PM2.5. To control particulate matter pollution, it is imperative to fix gaseous pollutants spewed into atmosphere from industries,” Anumita Roychowdhury, executive director, CSE, said.

There is no systematic as well as regular monitoring of the dangerous trend of SO2 converting into sulphate particles. Various studies have reported high levels of sulphate particulates in particulate matter.

The conversion rate of SO2 to sulphate varies from 0.1-2.81 per cent per hour in the winter and 0.1-6.01 per cent per hour in the summer, depending on the relative humidity and other weather parameters.

Sulphate levels in particulate matter

Source: Centre for Science and Environment, 2020

Not so simple

The SO2 norm for which the CEA is seeking to relax, is a criteria pollutant. Its presence over 20 μg / m³ (24-hour mean) or 500 μg / m³ (10-minute mean) can cause severe health damage.

The colourless gas affects the respiratory system and the functions of the lungs and causes irritation of the eyes. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract.

Typically, the background levels of SO2 in the ambient air of healthy environments are very low (below 2 μg / m³). The key source of SO2 in India today is coal-based thermal power stations.

Several studies have pointed that about 50 per cent of all human-made SO2 emissions in India is coming from coal-based thermal power stations. The Union Ministry of Petroleum and Natural Gas has taken cognizance of the sulphur issue in fuel

It has leapfrogged from the Bharat Stage (BS) IV, that had 50 points per million (ppm) sulphur to BS VI fuel, that has 10 ppm sulphur, this year. “This move has not only reduced sulphur, but will also help in reducing the overall pollution load from the transport sector by about 80-90 per cent.”

In 2015, the MoEF&CC introduced emission limits for TPPs. The power sector has been constantly pushing back to comply the norms. The initial deadline of 2017 has now been extended to 2022, after constant lobbying by the sector.

Installation of the FGD systems, that are used to reduce SO2 emissions requires an investment of about Rs 50 lakh a MW and would result in an escalation of power cost by 20-25 paisa a unit. Most power stations are unwilling to invest, fearing delays in recovery. For some stations, securing investments with existing bad loans remain a challenge.

CSE’s assessment shows that even the extended deadline will be missed by 65 per cent of the capacity. The non-compliance issue is being heard by the Supreme Court as a part of the Delhi air pollution issue.

Instead of pushing power stations to comply, the Union Minister of Power’s directions and the CEA’s denial of the problem by cherry-picking figures, producing biased reports without giving details on what happens to the SO2 emitted in the atmosphere by power plants and the attempts to water down the norms is worrisome, says Nivit Kumar Yadav, director, Industry Unit, CSE

The relaxation has been demanded under the pretext that different emission norms be suggested for different plants, based on their ambient air conditions.

“Several countries whose ambient air quality sulphur dioxides are low, have stringent norms on SO2. For 70 per cent of the total world coal capacity, the SO2 standards are below 200 μg / m³,” Vinay Kumar Trivedi, senior research associate, CSE, said.

An analysis by the CSE of 123,311 MW of coal-based thermal power capacity in the United States found 71,598 MW of capacity located in areas where the ambient SO2 concentrations were not deductible. Still, the country has regulations to limit emissions from coal-based thermal power stations.

Ambient air SO2 concentration in the power station rich states of the USA

Source: Centre for Science and Environment, 2020

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