- The concentration of sulphur dioxide, an atmospheric pollutant with health and climate impacts, shows a decreasing trend in India in the recent decade (2010-2020) compared to previous decades, according to a trend analysis.
- Even if growth of sulphur dioxide concentration has stabilised in the recent decade, the amount of concentration is still high, and India continues to be the largest emitter of the pollutant.
- Environmental regulations including those associated with coal-fired power plants, pollution control technolgies and India’s clean energy transition have played a significant role in bringing down concentration of sulphur dioxide in the recent decades but the government needs to continue enforcing the norms, experts say.
- Continued climate action aligned with India’s commitment to the Paris Agreement to mitigate climate change will aid in keeping sulphur dioxide concentrations in check.
While the concentration of sulphur dioxide (SO2), an atmospheric pollutant with health and climate impacts, shows a decreasing trend in India in the recent decade (2010-2020), compared to previous decades, due to environmental regulations and control technologies in place, its concentration is still high and is of concern, a trend analysis has said.
“Even if the trend is negative, or SO2 concentration has stabilised, the concentration is still high, and we have to do something about it; we’re still the largest emitter,” study lead author and climate scientist Jayanarayanan Kuttippurath told Mongabay-India.
“And what we have found is, from our analysis, that technology and environmental regulations have played a significant role in reduction in that trend. That’s a positive thing actually. So, the government should continue that; we should not be complacent,” added Kuttippurath at IIT Kharagpur’s Centre for Oceans, Rivers, Atmosphere and Land Sciences.
Replacement of the conventional fuel-based production (coal) in the power sector, iron and steel industries, refineries, and other fuel-demanding sectors with renewable energy sources would help to reduce the overall SO2 emissions in India, the scientists suggested. They also recommended building a long-term emissions inventory for India, especially for hotspots for future assessments and policy decisions. Emissions inventories are important tools for identifying the source of pollutants and target regulatory actions.
Sulphur dioxide is an air pollutant and in very humid conditions, it can be converted to sulfate aerosol, which can eventually affect the regional climate by modifying the radiative forcing (a measure of the influence of climate factors such as aerosols, greenhouse gases in warming or heating the planet), cloud reflectivity and rainfall. “Additionally, SO2 also reduces the visibility and contribute to the acid rain that damages the aquatic and terrestrial ecosystem, and other valuable properties and monuments. Therefore, SO2 at high concentrations affects air quality, ecosystem, visibility (e.g. haze formation) rainfall, and regional climate,” added Kuttippurath.
SO2 has an adverse effect on the human respiratory system and even short-term exposure to high levels might result in death, noted the study. As per the WHO air quality guidelines (World Health Organization 2021), the recommended 24 hour average SO2 concentration should not be more than 40 µg/m3 for protecting human health, it said.
The study examines the longterm changes in SO2 concentration in India from 1980 to 2020 and analyses the sources and factors shaping those changes. Scientists used ground-based and reanalysis data along with an emissions inventory to track changes in SO2 concentrations.
They observed a continuous increase in SO2 emissions from 1980 to 2010 coinciding with India’s energy demand for industrial growth and urbanisation.
“The temporal analyses reveal that SO2 concentrations in India increased between 1980 and 2010 due to high coal burning and lack of novel technology to contain the emissions during the period. However, SO2 shows a decreasing trend in recent decade (2010–2020) because of the environmental regulations and implementation of effective control technologies such as the flue gas desulphurisation (FGD) and scrubber,” authors write in the paper.
The study used data from Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) of NASA and Copernicus Atmosphere Monitoring Service (CAMS) set of satellites and airborne instruments.
“We examined the percentage change in trend values in the last decade compared to the previous decades. We find about a 50-60% reduction in trend values in 2010-2020 compared to 2000-2010. However, concentration is still higher in the last decade compared to that in the previous decades. This is the concern,” Kuttippurath said.
The Indo-Gangetic Plains, central and eastern India are the hotspots of SO2 pollution as these regions house a cluster of thermal power plants, petroleum refineries, steel manufacturing units, and cement industries, according to the study. These hotspots include rural areas.
India is considered the largest SO2 emitter in the world, according to a 2019 analysis by Greenpeace.
Another 2017 research noted India overtaking China as the world’s largest emitter of anthropogenic sulphur dioxide. “Since 2007, emissions in China have declined by 75% while those in India have increased by 50%. With these changes, India is now surpassing China as the world’s largest emitter of anthropogenic SO2,” the research said.
According to the latest analysis by Kuttippurath et al, coal-based thermal power plants (51%) and manufacturing and construction industries (29%) are India’s major sources of SO2 released from human actions. Biomass burning, chemical and fertiliser industries, and the petroleum industry also contribute to SO2 pollution. The contribution of biomass burning to the SO2 burden in India is less than one percent. Sulphur dioxide concentration is higher in winter and lower in pre-monsoon, the analysis shows.
Emissions from the two primary sources (coal-based power plants and manufacturing and construction Industries) are higher in the last decade (2000-2010) than in previous decades. But emissions from other sources such as transportation, chemical industries, and biomass burning went down in the last decade, trends reveal.
“The implementation of Bharat Stage norms on vehicular emissions, regulations for the power plant to use scrubber and FGD technology, and policies towards the production of renewable source of energy might be the reasons for the drop in SO2 emissions in India in the last decade (2010-2020),” Kuttippurath added.
“Majority of the coal-based thermal power plants in India use bituminous or sub-bituminous coal, or lignite, which contain 0.7% sulphur by weight. Furthermore, Indian coal (Gondwana coal) contains a lot of ash (35-45%) and has a low caloric value. Therefore, coal-fired power plants should be subjected to pollution standards, e.g., mandating existing coal-fired power plants to install FGD and scrubber systems can reduce SO2 pollution,” the authors stated.
But a large number of coal-fired power plants are yet to introduce FGD system.
Delay in the installation of FGDs
In 2015, India’s Ministry of Environment, Forest and Climate Change (MoEF&CC) notified stricter standards for coal-based thermal power plants to minimise pollution, including standards for sulphur dioxide emission. The Ministry identified nearly 166 GW worth of capacity needed to install pollution control retrofits, especially FGD systems to rein in sulphur dioxide.
However, most of the power plants missed the initial deadline of December 2017 for installing FGD and it was extended till June 2022. As per government data, only 20 power plants have installed FGD. “As per latest status, 16 units are on wet FGD and 4 units on DSI technology installed for de-sulphurisation of flue gas from coal-based thermal power plants,” said Minister of State (MoS) for Environment, Forest and Climate Change Ashwini Kumar Choubey in Lok Sabha.
There are 267 coal-based power plants in India.
India’s Ministry of Power recently wrote a letter to MoEFCC and sought a two-year extension for thermal power plants to install FGDs that control toxic sulphur dioxide emissions from plants.
In a notification issued on September 5, 2022 the environment ministry again extended the timeline to meet sulphur dioxide norms to December 31, 2027.
“It is quite evident that the MoEF&CC and the Central Pollution Control Board instead of strictly enforcing the emission norms, have given up on the demands of the Ministry of Power and have been extending the deadline by amending the laws to save the non-compliant thermal power plants (TPPs) from adversarial action,” legal analyst Debadityo Sinha told Mongabay-India.
Sinha at Vidhi Centre for Legal Policy, an independent legal research think-tank adds that although there has been some progress in installing FGDs in centrally-owned and privately owned TPPs, the state-owned TPPs have hardly made any considerable progress towards it.
However, a clutch of TPPs have installed the new technology and are getting positive results.
In 2018, National Thermal Power Corporation’s Dadri power plant installed Dry Sorbent Injection (DSI) system for SO2 reduction in compliance with 2015 norms. DSI systems inject dry alkaline sorbents are injected into the flue gas —combustion exhaust gas exiting a power plant-to remove common pollutants. As per a statement issued by NTPC Ltd, the PSU under the Ministry of Power, the flue gas emissions and particulate matter are well within the CPCB norms with high-efficiency ESP (Electrostatic Precipitators) in service in all the four 210 MW and two 490 MW units.
The financial burden is also a factor causing delays in the installation of FGDs.
A Delhi-based non-profit, Council on Energy Environment and Water (CEEW) found that only 1.5 GW out of 35 GW complies with the emissions norms and has installed flue gas desulphuriser (FGD) systems. It would cost the system Rs 14,300 crore in retrofits for reining in SOx emissions.
Another study by the Centre for Science, Technology and Policy (C-STEP) highlights that to comply with the emission standards, “power producers will have to invest 0.5–1 crore (Rs. 5-10 million) per megawatt for nearly 80% of the plants by 2030.” This study estimates an opportunity of around Rs. 2,50,000 crore (2500 billion) for the pollution control equipment industry over the next 15 years.
The C-STEP study also reveals that non-compliance with emission norms would result in 300,000-320,000 premature deaths and 51 million hospital admission cases due to respiratory disorders between now and 2030 in India.
Kuttippurath says India’s climate action goals, including its commitments to the Paris Agreement to reduce greenhouse gas emissions to limit global warming to well below 2, preferably to 1.5 degrees Celsius, compared to pre-industrial levels, will help reduce the dependency on coal for energy and curb sulphur dioxide emissions.
As per the updated Nationally Determined Contribution (NDC), non-binding climate-related targets for greenhouse gas emission reductions, India now stands committed to reducing the emissions intensity of its GDP by 45 percent by 2030, from the 2005 level, and achieving about 50 percent cumulative electric power installed capacity from non-fossil fuel-based energy resources by 2030.
Banner image: A thermal power plant in Haryana. Photo by Vikramdeep Sidhu/Wikimedia Commons.