- Current policies are not sufficient to substantially improve air quality in Kolkata and suburbs by 2030, a modelling study has said.
- Combustion of solid fuels by households and commercial sector (restaurants and roadside eateries) contributes to half of Kolkata Metropolitan Area’s fine particulate matter (PM 2.5) emissions, researchers said, batting for a switch to clean fuels.
- Advanced control measures, coupled with the control of non-technical emission sources, such as road and construction dust, may prove to be the most effective solution.
- Researchers batted for an airshed approach to managing future air quality in the Kolkata Metropolitan Area.
What’s the future of air quality in Kolkata? There’s unlikely to be an improvement if policies maintain status quo. Current policies and measures are not sufficient to substantially cut down fine particulate matter (PM2.5) emissions in West Bengal’s densely populated capital Kolkata and suburbs by 2030, a modelling study has said.
The study by International Institute for Applied Systems Analysis, Vienna (IIASA) and CSIR-National Environmental Engineering Research Institute (NEERI) researchers underscores that a marked change in primary particulate matter (PM 2.5) emissions in the Kolkata Metropolitan Area (KMA) between 2015 and 2030 is unlikely, even after complete execution of the existing measures.
“This means emissions are almost the same between 2015 and 2030. However, there is a marked decrease in sulfur dioxide emissions between 2015 and 2030 primarily due to planned policies such as flue-gas desulfurisation to remove sulfur dioxide from exhaust flue gases of fossil-fuel power plants,” IIASA scientist and lead author of the study Pallav Purohit told Mongabay-India.
The study area, the Kolkata Metropolitan Area, comprises the old city and surrounding districts of North 24 Parganas, South 24 Parganas, Howrah, Hooghly, and Nadia. Sprawling over an area almost half of the spread of Goa (1886.67 square km) and governed by three municipal corporations, KMA is home to 14 million as against the total Bengal population of 92 million.
On its launch in 2019, the National Clean Air Programme listed only Kolkata from West Bengal among 102 cities having air quality worse than the National Ambient Air Quality (NAAQ) standards. However, six more cities from the state were bumped up to the non-attainment city list, taking the state tally to seven non-attainment cities.
In 2017, West Bengal was one of the Indian states with the highest annual exposure to PM 2.5 levels, and it also had the highest number of deaths attributable to air pollution among states in the mid sociodemographic index segment that includes Karnataka, Telangana and Manipur among others, said the 2017 Global Burden of Disease study.
Between November 2018 and February 2019, Kolkata had 106 poor, very poor and severe air quality days while Delhi had 90 such days, making it “worse than Delhi” for that time frame, according to Kolkata-based NGO Kolkata Clean Air, a network of organisations /institutions and thousands of active citizens.
To address future emissions, Purohit and colleagues developed an emissions inventory (database of source of air pollution emissions in a geographic area during a specific time period) of air pollutants and greenhouse gases and used the GAINS-City model to analyse future emission scenarios for Kolkata.
For the emissions inventory, the scientists considered all the applicable national and city-specific policies expected to affect air pollution emissions in KMA, including those that look into solid waste burning and provision for LPG connections.
The inventory data with 2015 as baseline shows that in Kolkata and suburbs, known for its street food culture, combustion of solid fuels (such as coal, wood) in inefficient stoves by households and commercial sector (restaurants, hotels and roadside eateries) contributes to half of the fine particulate matter (PM 2.5) emissions.
“In KMA, roadside eateries are very common across the city, especially near busy crossings. Due to the easy availability and low cost of solid fuels such as coal and wood, they are still being used widely in this sector as primary fuel along with kerosene and LPG,” said Purohit. Other major emission sources for the Kolkata metropolitan area include power plants, transport (heavy-duty trucks), waste and industrial processes.
Purohit and colleagues recommend deployment of advanced technologies targeting primary pollutants (such as PM 2.5 and PM 10) in cohesion with local solutions that can clamp down on non-combustion emissions such as road and construction dust, to tackle future emissions in the Kolkata Metropolitan Area.
They also advocate changing tracks to a low carbon pathway by switching to cleaner and more energy-efficient fuels in key economic sectors including the city’s vibrant food industry with its reported two lakh street food vendors catering to over 10 million people daily.
“Most important message of our study is that we already have national and state-level policies and plans to curb air pollution in power, industry and transport sectors. All we need is strict enforcement,” Pallav Purohit said.
Airshed approach to clean air
“Solid fuel burning, especially in the Kolkata suburbs, should be reduced but citizen action is also crucial for enforcement. Public awareness plays an important role in curbing emissions,” said NEERI’s Dipanjali Majumdar, highlighting the airshed approach to creating the inventory and running the model taken by the authors.
Airshed refers to a geographical region (in this case KMA) that tends to share the same flow of air.
“The top contributors to air pollution in Kolkata city may not be the major contributors to poor air quality in Kolkata and its suburbs taken together (KMA),” said Majumdar highlighting the nuances in airshed approach.
“So an updated emissions inventory can reveal what worked and what didn’t and how strategies can be customised across cities that come under the airshed. We now need a source apportionment analysis for KMA to understand the regional contributions as we did for Delhi National Capital Region (NCR),” said Purohit.
The NCR covers the whole of National Capital Territory of Delhi (Delhi NCT) and certain districts of Haryana, Uttar Pradesh and Rajasthan, covering an area of about 55,083 square km.
For example, taking the 2015 baseline data, Purohit, said that despite the lower primary emissions in Delhi (Delhi National Capital Territory), air quality in Delhi is worse as compared to Kolkata because more than 60 percent pollution in the national capital is linked to sources (such as stubble burning) outside the immediate jurisdiction of the national capital territory of Delhi.
In Delhi city, the major fraction of PM 2.5 emissions comes from the transport sector (including non-exhaust emissions) despite improved public transport and CNG buses and three-wheelers because of the large vehicle fleet whereas in Kolkata, the vehicular fleet, is more managed, Purohit and Majumdar said.
“Even though the ban on 15-year-old vehicles is not totally implemented, it has shown effects on air quality, which reinforces the importance of stringent implementation of air control measures,” said Majumdar.
“Further, in Delhi NCT you will not find any brick kilns but in Kolkata, brick kilns are present even on the banks of the river Hooghly in KMA region,” added Purohit.
Anumita Roychowdhury of Centre for Science and Environment, who was not associated with the study, also echoed the study authors in taking the airshed approach to managing air quality, taking a leaf out of Delhi NCR.
“If you move along the highways connecting Kolkata you will see the use of solid fuel in roadside eateries and also spot burning of waste. Big learning emerging from Delhi and other cities of India is that you need an airshed regional approach. Pollution is not confined to the boundary of the Kolkata city. What you are doing for Kolkata should be done for the entire urban agglomeration of KMA,” Roychowdhury told Mongabay-India.
The study comes amid the West Bengal government drawing up an action plan to clean Kolkata city’s air, recognising the substantial contribution of coal or wood-fired ovens and road dust to air pollution. The action plan includes the provisions of supplying LPG cylinders to food vendors who use coal or wood-fired ovens for cooking, deployment of water-sprinkling vehicles to rein in road dust, penalising garbage burning in the open and cracking down on vehicles that are over 15-years-old and plying illegally.
The West Bengal Pollution Control Board, which has been recently apprised of the findings from the final report on source apportionment study by NEERI, said Kolkata’s air quality is “one of the best in last so many winter months” courtesy dust suppression and control of open burning of waste, including leather waste. It tweeted that a perceptible improvement was observed in the air quality of Kolkata and suburbs from December 1 to 15th in 2018 and 2019.
According to board officials, there are projects in the pipeline that target potential future emissions for the city expected to see growth in its vehicular fleet, population and energy demand.
Purohit said the action points in the plan are a step in the right direction because they address non-technical air pollutants such as road dust and follow a low carbon pathway of switching to clean fuels, but questioned the monitoring and enforcement.
“Overall, we know that annual standards for PM 2.5 will require substantial cuts to meet the NAAQs. We have to understand the nature of action that has already been taken and what more needs to be done,” said Roychowdhury.
For example, Kolkata has shifted industries out of the main city, one coal-based plant is operating in the city while the other one was shut down and it has banned vehicles that are over 15 years old from plying in the KMA area, noted Roychowdhury.
“If this is baseline action which is already going on for Kolkata and even after doing this if levels are still higher than the national standards, we now have to very clearly take up areas of interventions such as the number of vehicles which are increasing. Then you have the problem of open burning, small industries and construction sector. These are the areas that have to be prioritised for taking solid action to tackle future emissions,” added Roychowdhury.
Solutions for 2030
As for 2030, the model projections show Kolkata and suburban air quality is not likely to show marked improvement even after complete implementation of the current crop of policies unless additional strategies and policy measures considering both combustion and non-combustion sources (such as road dust) are put into effect.
In fact, the authors warn in the study that air quality status may degrade further unless the immediate and complete implementation is not carried out of the policies already in place.
The “most effective solution”, as per the study, could be the application of advanced control measures coupled with the control of non-technical emission sources. Non-technical emission sources consist of non-exhaust emissions (road dust, tire and brake wear) in the transport sector, unpaved roads, trash burning, construction dust, etc.
Advanced control technology refers to the application of the best available technologies and advanced air pollution control policies. For example, the use of high-efficiency deduster (HED) for particulate matter control for future years is considered instead of electrostatic precipitator (ESP) in the power sector.
This cocktail of advanced technology, policy and control of non-technical sources through city-specific policies, could slash levels of key air pollutants by half (51 percent for PM 2.5 and nitrogen oxide by 54 percent) with a cost implication of €1.18 billion by 2030.
Low carbon policies may also be able to substantially reduce key air pollutants with the additional benefit of reduced emissions of greenhouse gas (carbon dioxide by 24 percent in 2030) with a running cost of €0.70 billion, the research suggests.
The low carbon pathway focuses on switching to cleaner and more energy-efficient fuels in key economic sectors without any advanced control technology, which in Kolkata’s case would translate into targetting the four coal-based thermal power plants in Kolkata metropolitan area and switching to LPG or electricity (induction cookstoves) for households.
A survey conducted as a part of this study by NEERI, Kolkata, found that approximately 52 percent of the registered hotels and unregistered eateries were using LPG and 48 percent were using fuelwood, coal and kerosene.
“In the low carbon scenario, it is possible to use LPG (or electricity) by all the small food businesses. We assume that 10 percent coal combustion remains for tandoor activity with advanced cookstove for hotels and small food businesses in this scenario,” said Purohit.
Majumdar adds that with vehicular fleet set to expand, more controls and measures, (especially for large vehicles that are responsible for the roadside component of air pollution) will be required to add to the arsenal of future policies.
“Maintaining the status quo will not be good for us and concerted time-bound efforts by citizens and government are crucial,” Majumdar said.
Ajaay Mittal of Kolkata Clean Air agreed that behaviour change is essential.
“Our perception surveys show that citizens in Kolkata are aware of the magnitude of the problem. We are trying to affect behaviour change through community projects such as those that deal with waste disposal. Additionally, another focus is to highlight vulnerable groups that experience long-term exposure to pollution. For example, we did a survey on how air pollution impacts traffic police that helped draw attention to their plight,” Mittal told Mongabay-India.
Majumdar, D., Purohit, P., Bhanarkar, A. D., Rao, P. S., Rafaj, P., Amann, M., … & Srivastava, A. (2019). Managing future air quality in megacities: Emission inventory and scenario analysis for the Kolkata Metropolitan City, India. Atmospheric Environment, 117135.
Banner image: Vehicles on Howrah Bridge. Photo from Unsplash.