The glass industry requires a high-temperature manufacturing process that exceeds 1500°C, typically using fossil fuels that emit harmful gases, particularly sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), which are extremely harmful to human health and the environment. As a significant contributor to air pollution, it is essential to monitor emissions from glass production. In India, the regulations of these emissions are under the Ministry of Environment, Forest and Climate Change (MoEFCC) and with the Central Pollution Control Board (CPCB) serving as the primary implementing authority.
In India, air pollution has been a major concern across all states of India, particularly in industrial areas with a high concentration of manufacturing companies. Therefore, to address the growing concerns over industrial pollution, India has established specific emission standards depending on the type of furnace and fuel used.
These standard emission implementations work for the broader framework of the Air (Prevention and Control of Pollution) Act, 1981 and the Environment (Protection) Act, 1986 which has been enforced strictly as the country launched its National Clean Air programme (NCAP) in 2019. Under the National Clean Air programme, the major glass manufacturing hubs such as Gujarat and UP are under strict monitoring for SO₂ and NOx emissions.
Why is Monitoring of SO₂ and NOx Mandatory?
The monitoring of SO₂ and NOx standard for the Glass Industries in India is mandatory as these pollutants can pose a major harm to the human health and the environment. Under the national and international agreements, India has committed to reducing industrial pollution by 45% by 2030.
In 2025, the cities in India continue to get exposed to air pollution which is above the WHO’s recommended levels and the major contributor is the industrial emissions, among these emissions the sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) are the dangerous pollutants that can react in the atmosphere to form sulfuric and nitric acids, which are the primary source of acid rain that can cause serious damage to the infrastructure, the vegetation, human health, reduction in visibility, and affects the climate change and thereby global warming.
Therefore, the monitoring of the sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) is mandatory as it affects the entire ecosystem of the Earth. With monitoring of these pollutants, we can identify the major root cause and areas so that we can implement mitigation and implement strategies to reduce the emissions.
Understanding of SO₂ and Nox
The sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) are the two dangerous pollutants that are released by the glass industry. These emissions are a result from the combustion of fossil fuels such as furnace oil, natural gas, and coal which are used in the glass industry, that can harm our environment, vegetation and health.
- Sulfur Dioxide (SO₂)
The sulfur dioxide (SO₂) can cause respiratory problems in humans and increase health issues in patients with existing heart problems. It is produced by the burning of sulfur containing fossil fuels such as oil and coal.
These fuels are used to maintain the furnace temperatures above 1500°C, which is necessary to melt raw materials for glass production such as sand (silica), soda ash and limestone, when the sulfur in this fuel burns, it reacts with the oxygen in the air to form thin particles of sulfur dioxide (SO₂) of PM2.5 (Particulate Matter) that can travel to your lungs and cause serious health issues, especially among children and older population in the country.
- Nitrogen Oxides (NOₓ)
The nitrogen oxides (NOₓ), which are formed during the high-temperature combustion process in glass manufacturing include nitric oxide (NO) and nitrogen dioxide (NO2). The combustion produces two main types of nitrogen oxides (NOₓ) such as thermal NOₓ and fuel NOₓ.
The fuel NOₓ is produced when the nitrogen in the fuel reacts during the combustion and the thermal NOₓ is produced when the oxygen from the air reacts with the nitrogen at high temperature inside the furnace. Any exposure to the fine particles of nitrogen oxides (NOₓ) can cause a range of respiratory health issues, such as difficulty in breathing, coughing, asthma and bronchitis.
Since, the glass manufacturing requires operating consistently at high temperature, they release fine particles of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) into the air, that forms acid rain, smog and dispersion of fine particulate matter (PM2.5) which significantly degrades the air quality and cause harm to the environment, ecosystem and the human health.
New Regulatory Standards for the Emission of the Glass Industry
The Ministry of Environment, Forest and Climate Change (MoEFCC) in collaboration with the Central Pollution Control Board (CPCB) under the amended rules on Air (Prevention and Control of Pollution) Act, 1981 and the Environment (Protection) Act, 1986 released the air pollutant standards for the glass industry in India. The MoEFCC has implemented specific emission standards for SO₂ and NOx for the glass industry, based on the fossil fuel used for production.
The emission standards for the glass industry in India for SO₂ and NOx are strengthened after the 2018 amendment by the Ministry of Environment, Forest and Climate Change (MoEFCC). Before the 2018 amendment, there were no specific standards or limits.
However, recognizing the glass industry’s growing contribution to air pollution, particularly in the glass city of India, Firozabad, the government of India have improved its guidelines by identifying the root cause and setting targeted standards. If the glass manufacturers do not comply with these given standards, there are clear penalties, including suspension of operations and revocation of the environmental clearances.
The mandatory compliance regulations on emission standards for SO₂ and NOx for the glass industry are listed in the amendment of Schedule I of the Environment (Protection) Rules, 1986 and are listed as follows:
- SO₂ Emission Standards:
500 µg/Nm³ for natural gas-fired units
1,500 µg/Nm³ for units using other fuels
- NOₓ Emission Standards:
- 1,000 µg/Nm³ for units using other fuels
Stack Height Criteria for SO₂ and NOₓ
The existing rules implemented under the Environment Protection Act, 1986 and the policies enacted by the Pollution Control Committees (PCCs) or the State Pollution Control Boards (SPCBs) of the stack height criteria to ensure that the emissions released during the glass production and manufacturing are released at a height that that allows the emissions to spread safely into the air, thereby minimizing ground-level pollution and health risks.
Although the 2018 amendment does not have a new stack height criterion, the regulations for the emission standard of SO₂ and NOx, makes it mandatory to comply with the existing rules implemented under the Environment Protection Act, 1989, notified on the 21st February 1991.
The notification makes it mandatory for industries to ensure that the stack emissions are being released at a height depending on the different fuel types, industry and combustion capacity, the height is mostly 30 meters for various industries including the glass industry.
Monitoring and Compliance Authority for the Glass Industry
Monitoring of the glass industry for the SO₂ and NOx emissions is important so that you can keep a check on the rate of emissions and compliance of the manufacturers. Every glass industry must install a Continuous Emission Monitoring System (CEMS) to track the emissions consistently to make sure that the emissions are within the permitted limit. It is also mandatory for industries to monitor and maintain appropriate stack height for the dispersion of the emissions.
The State Pollution Control Board (SPCB) and the Pollution Control Committee (PCC) are the regulatory authorities in overseeing and monitoring the compliance issues of the glass industry. While the Ministry of Environment, Forest and Climate Change (MoEFCC) is the authority that implements the policies. There are set rules for non-compliance with these standards for the glass industry.
You can be faced with legal penalties and fines, and if there is still no compliance, you could potentially lose your license thereby suspension of operations, and your environmental clearance may be revoked. In serious cases, you could also land up in the environmental courts or tribunals.
Compliance Strategies for the Glass Industry Manufacturers
The glass industry manufacturers in India require compliance with the environmental regulations to manage and reduce the emissions of air pollutants mainly SO₂ and NOx. Every glass manufacturer must adhere to the environmental regulations, safety measures, and have Environmental Impact Assessment clearance with international certifications such as ISO.
Compliance with the emission standards not only ensures legal compliance under the Central Pollution Control Board (CPCB) and the Ministry of Environment, Forest and Climate Change (MoEFCC) but also helps you commit to sustainable practices in your business to improve the environmental footprint. A successful compliance strategy for the glass industry manufacturers is listed below:
- Improvement in Fuel Quality
Improving the fuel quality in glass production can help to reduce the SO₂ and NOx; you can also switch to low-sulfur fuels such as piped natural gas (PNG) or liquified natural gas (LNG) to reduce the SO₂ emissions.
High-sulfur furnace oil or petroleum coke must be avoided unless the glass manufacturing industry is equipped with good gas treatment plants. Regularly testing the fuel for sulfur content to maintain the emission standard set by the MoEFCC is necessary. Therefore, using cleaner fuels, monitoring of the fuel can help achieve long-term sustainable operations.
- Install Pollution Control Equipment’s
You can also install pollution control equipment such as flue gas desulfurization (FDG) systems, which help remove the SO₂ from the exhaust gas of fossil fuels, such as wet scrubbers or dry sorbent injection systems, to capture the sulfur dioxide (SO₂) before it is released into the atmosphere.
To reduce nitrogen oxides NOx, you can use Selective Non-Catalytic Reduction (SNCR) or Selective Catalytic Reduction (SCR) systems to reduce NOx emissions and also equip bag filters or electrostatic precipitators (ESPS) to manage particulate matter (PM2.5) emissions in the atmosphere.
- Regulatory and Environmental Compliance
Environment (Protection) Amendment Rules, 2018 has released compliance regulatory regarding the specific standards of sulfur dioxide (SO₂) and nitrogen oxides NOx, where the standards for SO₂ emissions are 500 mg/Nm³ when using natural gas and 1500 mg/Nm³ for other fuels and the standard for NOx emissions is 1000 mg/Nm³.
Staying updated with the CPCB guidelines and state specific pollution control rules is important for EPR compliance. You must also conduct internal audits and submit Environmental Statement Reports annually as per the Environmental Protection Act, 1986.
- Install and Adopt Continuous Emission Monitoring Systems (CEMS)
Implementing the Continuous Emission Monitoring Systems (CEMS) for your glass manufacturing industry to monitor the SO₂ and NOx emissions as mandated by SPCB will ensure regulatory compliance and reporting of regular emissions for large furnaces.
Ensuring a real time emission data of your glass manufacturing unit is linked to the State Pollution Control Board (SPCB) and Central Pollution Control Board (CPCB) servers. You must also measure and maintain monitoring equipment to ensure data is accurate and avoid penalties. Getting a NOC from Pollution Control Board is crucial.
- Enhance the Manufacturing Process
You can enhance the operation parameters such as temperature, air-fuel ratio, burner designs, etc., to minimise the formation of nitrogen oxides NOx. Implement controlled combustion and low NOx burners to reduce nitrogen oxide formation during high-temperature operations in glass production.
Maintaining furnace insulation and correctly weighing, mixing and feeding the prepared batch of raw materials in the furnace to reduce fuel consumption and emissions.
- Research & Development for Technology Upgradation
To stay under the standard emission limits of SO₂ and NOx, exploring alternative or advanced technology upgrades is essential, such as adopting better melting technologies like electric furnaces for special glass production. Collaborating with R&D institutes to research and develop new technologies can lead to more sustainable, cleaner, and energy efficient furnace designs.
How can Indian Glass Industries Align with Environmental Goals?
India’s environmental goal is to achieve net-zero emissions by 2070. The Indian glass industries can align with national environmental goals by using sustainable practices for their business operations, such as increasing glass recycling practices, using technologies that are energy efficient, and complying with the specific emission standards set by the Central Pollution Control Board.
Business owners in Indian glass industries must proceed with securing environmental clearance, BIS registration, e-waste recycling authorization, and more.
By implementing these sustainable practices in glass manufacturing, you can commit to a long-term environmental goal for the country.
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In a Nutshell
The Ministry of Environment, Forest and Climate Change (MoEFCC), along with the State Pollution Control Board (SPCB) and the Pollution Control Committee (PCCs) are implementing and monitoring the emission standards of industries in India. The 2018 amendment to the specific emission standard of SO₂ and NOx for glass industries is an important move toward reducing industrial air pollution in the country. As India continues to facethe impacts of air pollution, and the AQI always exceeds the normal levels mostly in the urban and industrial areas, using sustainable practices for all businesses is necessary.
One of the industries that is significantly contributing to the air pollution in India, is the glass industry. The glass manufacturing industries have to regularly monitor and maintain the specific emission standards set by the Ministry of Environment, Forest and Climate Change (MoEFCC). High-temperature glass furnaces are extremely energy-intensive and without proper controls, can release a large quantity of harmful gases such as sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) into the atmosphere.
These pollutants can thereby contribute to acid rain, smog, and respiratory health issues such as asthma and bronchitis and can also degrade the ecosystem and the infrastructure, making their management and monitoring an important aspect of the business. Therefore, these mandatory emission standards and mandatory installation of the Continuous Emission Monitoring Systems (CEMS), make a more transparent and technologically driven approach to improve air pollution in the country.
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Frequently Asked Questions
What is the limit of the NOx emission standard set by the Ministry of Environment, Forest and Climate Change (MoEFCC) for the glass industries?
The limit of NOx set by the Ministry of Environment, Forest and Climate Change (MoEFCC) for the glass industries is 1,000 µg/Nm³ for units using other fuels.
What is the limit of the SO₂ emission standard set by the Ministry of Environment, Forest and Climate Change (MoEFCC) for the glass industries?
The limit of SO₂ emission standard set by the Ministry of Environment, Forest and Climate Change (MoEFCC) for the glass industries for natural gas-fired is 500 µg/Nm³ and for other fuels is 1,500 µg/Nm³.
What is the air quality status of India currently?
The air quality in India is still unhealthy, the particulate matter (PM2.5) concentration is currently 10.1 times more than the normal air quality index set by the World Health Organization.
Where is India ranked in terms of Global Air Pollution?
India is known as one of the polluted countries in the world, often in the top 5. In 2024, India is ranked as the top 5th most air polluted country globally according to the IQAir. There have been improvements in the PM2.5 but Delhi remains the most air polluted capital city.
What are sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) emissions?
Sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) are pollutants released by various manufacturing industries, particularly the glass industry. These pollutants can form sulfate and nitrate particles in the atmosphere, which are transported away from the emission source and dispersed through the air. Emission of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) is harmful for the environment, human health and the vegetation.
How can we reduce the emissions of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ)?
You can reduce the emissions of sulfur dioxide (SO₂) by using coal that contains less sulfur. You can also install equipment’s to monitor and manage the emissions. To reduce the emissions of nitrogen oxides (NOₓ), you can use low-NOₓ burners, selective catalytic reduction (SCR) systems, or other advanced combustion technologies that minimize NOₓ formation during the manufacturing processes.
Who implements the emission standards for glass industries?
In India, the Ministry of Environment, Forest and Climate Change (MoEFCC), along with the Central Pollution Control Board (CPCB), implements, monitors, and ensures compliance with emission standards for the glass industry.
What is the Stack Height Criteria for sulfur dioxide (SO₂) and nitrogen oxides (NOₓ)?
The Central Pollution Control Board (CPCB) in India has made the Stack Height Criteria for sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) mandatory. The emission for SO₂ and NOₓ is determined by a formula and a minimum height requirement.
The formula used is H = 14(Q)0.3, where H is the stack height in meters and the emission rate is Q of SO₂ in kg/hr. A minimum stack height of 30 meters (90 feet) is mostly required for the emissions.
