1 2 3

Controlling Pollution in Coal Power Plants

Q&A with Shayak Sengupta, a Fulbright-Nehru Student Research Fellow who is conducting research on the cost, feasibility and effectiveness of air pollution control technologies in coal-fired power stations in India.

Shayak Sengupta is a Fulbright-Nehru Student Research Fellow and has recently graduated from Rice University in Houston, Texas. Although his family hails from India, Sengupta was born and brought up in the United States. His work has focused mainly on life cycle assessment or carbon footprints, specifically using the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model developed by Argonne National Laboratory to study the footprints of fossil fuels in transportation.

As part of the nine-month fellowship, Sengupta is studying air pollution control technologies at coal-fired power plants in India. He is working on the project at the Indian Institute of Technology Kanpur.


What are some of the main problems with India’s coal-fired power plants that make them heavy air polluters?

Currently, the vast majority of Indian coal power stations lack equipment to control emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx). Both pollutants are the products of fuel combustion, with sulfur dioxide coming from the sulfur naturally present in the coal, and nitrogen oxides coming from the nitrogen present in the air at high combustion temperatures.

After being released into the air, the pollutants react with ammonia, mostly from agriculture, to produce solid particulate matter. Both pollutants also contribute to acid rain, which pollutes waterways. Nitrogen oxide emissions also contribute to ground-level ozone formation. Ozone harms respiratory airways and reduces crop yields.

Furthermore, most coal of Indian origin has high ash content and low energy content relative to, say, coal mined in the United States, requiring more of it to be burned to produce the same amount of electricity.


Is it possible to make these coal-fired power plants environment-friendly and still retain their economic viability? Are there any successful examples that India can follow?

There are technologies currently used in the United States, Europe and China that control emissions and are economically viable in those countries. One purpose of my project is to find out if these would be economically viable in India. I’d like to estimate the cost per kilowatt hour electricity to install and use these technologies in India using publicly available data. To my knowledge, there are currently no country-wide cost estimates for the Indian context. While more India-specific data are needed, a first estimate, even with some uncertainty, would be a crucial step forward to fully understand the impacts of Indian coal power.


You are primarily studying two types of pollutants—sulfur dioxide and nitrogen oxides—and how they get converted to particulate matter. Why have you focused on only these two and not included a major polluter like carbon dioxide in your study?

Particulate matter comes from sulfur dioxide and nitrogen oxide emissions. It also comes from black carbon (soot) and organic carbon—two other classes of pollutants emitted from fuel combustion. Particulate matter poses the most immediate challenge for India due to its respiratory and cardiopulmonary health impacts. Particulate matter is also a carcinogen. In India, the vast majority of sulfur dioxide comes from coal combustion and a large portion of the nitrogen oxides comes from coal power as well. Compared to transportation and other sources of pollution, controlling emissions from coal power plants is relatively easier because they are point sources. That is, while other sources of pollution are diffuse and harder to quantify, coal power stations are stationary and relatively constant as they operate 24 hours a day throughout the year.

Another reason is that while renewable energy is growing, coal power is also growing and will continue to grow in India to meet growing electricity demand. In my own analysis thus far, I compared the number of coal-powered units between 2014 and 2015 using Government of India data, and the number jumped by over 100.

I decided to not focus on carbon dioxide because particulate matter poses more significant, urgent health impacts in India, and carbon capture and sequestration used to control carbon dioxide emissions is still in its infancy in terms of use. To my knowledge, there are only a few wide, industrial-scale uses of [carbon capture and sequestration] around the world, with the costs still being prohibitive.


Please tell us about the models that you are using to quantify the pollutants. Will predictions based on these models be reliable?

I’m using the Weather Research and Forecasting with Chemistry (WRF-Chem) model. A consortium of international researchers develops WRF-Chem, and the National Center for Atmospheric Research and the National Oceanic and Atmospheric Administration in the United States maintain it.

The model, temporally and spatially, simulates the meteorology and chemical reactions that happen in the atmosphere over India with appropriate input data. It then outputs simulated ambient pollutant concentrations over time and over a geographic area, which can be compared to on-the-ground measurements from monitoring stations.

The most important input that goes into this model is an accurate estimate of pollutant emissions. With India’s rapidly growing economy, emissions estimates from a few years ago can be outdated. While it can be a challenge to obtain accurate emissions estimates, several Indian research groups have published scientific papers using WRF-Chem over India. Overall, the simulated concentrations from models will not match exactly with measured concentrations, but they nonetheless do a pretty good job to capture trends and the general picture.

Right now, my research plan looks at technology implementation scenarios on a country-wide scale to see the effect on ambient air quality. This will require a careful inventory of all the coal power generating units in the country, current and proposed. So, you can say the methods I’m using are both general and specific. I intend to use U.S. Environmental Protection Agency cost estimating methodology with the substitution of relevant Indian parameters. I hypothesize that the calculated costs, along with the predicted pollutant concentrations from control technology installation, will warrant further action to limit sulfur dioxide and nitrogen oxide emissions.


Do you plan to present cost-benefit analysis of using pollution control technologies in Indian coal-fired power plants and would that include health impacts?

At this time, my focus is to quantify costs as best I can. Other researchers have studied the health impacts of Indian coal power plants, and my work can extend that to understand the health benefits of installing pollution control equipment. To do this though, I will need pollutant concentrations simulated by the model as well the cost estimates from my work.

A challenge during this kind of policy-relevant work is that the policy may change and India's economy is growing, including the growth of coal power. So, keeping track of a changing country can be difficult with extensive analyses. Nonetheless, I hypothesize that the public health benefits from decreased pollution will most likely outweigh the costs to install pollution control equipment.


What is your opinion about the proposed* emission limits for coal-fired power plants in India? What kind of efforts and incentives do you think would be needed to implement them?

The way the proposed limits are written currently, they do not apply to units constructed between 2007 and 2016, so it will be interesting to see the results of my analysis. For units to be installed in 2017 and after, and any proposed units under construction with an environmental clearance, the limits are much more in line with other countries such as China and the European Union.

I think, enforcement would be the key to implement these limits because you can have pollution control equipment installed, but if they’re turned off or the limits are not enforced through monitoring, it doesn’t do any good.  Another incentive that could help in pollution control is operational efficiencies. If plants operate more efficiently, they consume less fuel at a lower cost and they also emit less. This is a win-win for industry and the public.

In the United States, with the passing of the Clean Air Act Amendments in the 1990’s, many coal power plants had to limit their sulfur dioxide and nitrogen oxide emissions. The U.S. government set up a successful cap-and-trade program to limit these emissions. This type of program sets a national cap on the amount of pollutants that can be released per year, with the yearly amount decreasing over time. Industry and pollution sources then buy and sell permits that allow them to emit a certain amount of pollution. While this may be a long way away for India, I think it could provide the most flexible, market-oriented solution for India.


Why did you choose this subject for your project? What further research do you plan to do in this area?

I got interested in energy, climate change and air pollution as an undergraduate working with Dan Cohan, an atmospheric scientist, at Rice University. Most of my undergraduate work involved carbon footprint calculations of energy use in the United States. When the opportunity for a Fulbright came up, and with air pollution in India getting increased attention, India looked like an ideal setting professionally and personally, to do relevant research.

Depending on how my work continues here, I’d like to extend it to incorporate estimating health impacts I mentioned earlier. IIT Kanpur is also one of the best places in India to do my work because of the extensive expertise of the faculty members and the computational resources available. I intend to pursue a Ph.D. back in the U.S. after my Fulbright-Nehru grant. The professional collaborations I establish here will be relevant for my graduate research. There are many avenues to do policy-relevant impactful research on energy, air pollution and climate change in India.


*Note: The Ministry of Environment, Forest and Climate Change, Government of India, recently finalized the emission limits discussed in the Q&A. The finalized standards are different than the proposed ones, as they apply to all coal power plants in India—existing and under construction. To know more, please see The Gazette of India document.