Whether it’s plastic containers, clothes, home appliances, the detergents and medicines we use, the transport we choose or the heating in our homes, countless everyday objects and business processes require petroleum-derived substances for their operation or manufacture.
As a result, oil refineries are essential for producing the raw materials we need to make both our home and work lives easier in any social or economic sphere. Refineries are industrial plants that employ a range of chemical processes to transform crude oil into useful products. Once refined, these products then become highly valuable because of their wide range of potential uses in other industrial processes.
At the same time, these refining processes are one of the most significant contributors to air pollution (Galvan, L.E., 2007), both near the facility and further afield, and can dramatically worsen the air that we all breathe.
These various oil refining processes are the oil industry’s principal source of air emissions. They release gases such as carbon monoxide, sulphur dioxideSulphur dioxide (SO2) is a colourless gas with a pungent odour that causes an irritating sensation similar to shortness of breath. Its origin is anthropoge...
Read more, nitrogen oxides and volatile organic compounds into the air, as well as emitting high concentrations of a harmful combination of small chemicals in both a solid and liquid state, known as suspended particles or particulate matterAtmospheric particulate matter are microscopic elements suspended in the air, consisting of solid and liquid substances. They have a wide range of sizes an...
Read more.
In 2022, the world’s oil refinery capacity almost reached 102 million barrels per day. Overall, global refinery capacity has nearly doubled in the past fifty years, experiencing the largest growth during the 1970s.
Despite the fact that the oil industry is one of the most regulated sectors in the world and its emissions are subject to strict legislation, it is still essential to develop innovative refining processes since refineries can generate more than 800 different toxic chemicals. (Adebiyi F.M., 2022).
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At the same time, the use of air quality sensors at oil facilities is necessary for monitoring emissions from the various refinery processes. It is the best way to collect reliable, accurate data and prevent polluting emissions from being released into the air.
Being able to analyse measurements and react to them in real time helps to reduce the potential health risks for oil industry workers and maintain air quality levels for residents, and not just those in nearby areas. Because of the wind, emissions from the petrochemical industry can travel hundreds of kilometres from their point of origin. Furthermore, applying suitable controls to crude oil processing emissions helps protect water and soil, as well as the flora and fauna in the environment.
“The petroleum industry represents one of the chief latent threats for the environment and influences ecosystems and subsequently all living organisms, including human beings.” (Monteiro A. et al., 2017).
Oil and Gas Extraction Processes
Petroleum is a mixture of organic liquids and gases (mainly hydrocarbons) found inside the earth’s crust. The main constituent gas of petroleum is natural gas, which is mostly composed of methaneMethane, known chemically as CH₄, is a gas that is harmful to the atmosphere and to living beings because it has a high heat-trapping capacity. For this ...
Read more/">methane (CH4), whereas the main liquid component is crude oil.
The bitumen state of crude oil is the result of millions of years of anaerobic or oxygen-free microbial decomposition of large amounts of dead organisms, built up underground and subjected to high pressure.
The oil industry is the largest industrial sector in the world, refining crude oil and processing natural gas to produce countless useful substances, such as petrol or asphalt, and many others that are used as raw materials in other industrial processes.
During the refining process, which is highly energy-intensive, crude oil is separated into heavy products like tar, less heavy products like diesel and kerosene, and lighter products (which are the most valuable), such as petrol.
Refining techniques require petroleum to be separated into its different components. Then, these components undergo various conversion processes to give each derivative homogeneous characteristics.
While the very first refineries used physical separation processes before moving on to dry and atmospheric fractional distillation techniques, today’s oil industry employs a range of methods based on the use of heat, catalysation, pressure and chemicals. This way, it can comply with current regulations as it transforms oil into the world’s most in-demand petrochemical products.
Main Sources of Air Pollution from Refineries
Oil extraction is a complex process involving several operations using advanced technology. This process generates greenhouse gas (GHG) emissions such as carbon dioxide (CO2) and methane (CH4). Refineries are the world’s third largest GHG emitter. The principal environmental damage caused by the oil industry is due to its gaseous emissions (Damian, C., 2013), being responsible for 6% of net global industrial emissions.
At a refinery, emissions are produced at various stages as the crude oil is separated into different fractions. As a result, there are numerous points during the refining process that, together, substantially contribute towards the deterioration of air quality by emitting the following by-products:
- Polycyclic Aromatic Hydrocarbons (PAH). This is the term used to denominate a group of more than 100 substances produced by the combustion of oil, coal and petrol, among other things. They usually combine and adhere to dust particles. They can also react with sunlight and other substances suspended in the air. Excessive or long-term exposure to PAH can cause skin and eye problems, increase the risk of cancer and impair the immune system’s ability to fight infections.
- Sulphur Dioxide (SO2). While 98% of waste sulphur produced by refineries can be processed in desulphurisation and sulphur recovery plants, when it is burnt, it is released into the atmosphere in the form of sulphur dioxide. This colourless, unpleasant-smelling gas is a highly toxic irritant that can cause strokes and lung cancer.
- Nitrogen Oxides (NOx). These are yellowish, intense-smelling gases released by the burning of hydrocarbons. As they are soluble in water, they can produce nitric acid (NO2). These harmful gases can cause headaches, dizziness, vomiting and general weakness, as well as irritate the eyes and airways. They can also cause bronchitis and pulmonary oedema, and prolonged exposure can even lead to death.
- Carbon Monoxide (CO). This odourless, flammable gas does not immediately cause any irritation, so it can easily go unnoticed. However, when inhaled, it can cause confusion, dizziness, headaches and even fainting. Prolonged exposure can lead to neurological and cardiovascular problems.
- Hydrogen Sulphide (H2S). With its typical smell of rotten egg, when combined with CO2, this by-product forms acid gas. It is highly toxic and flammable, and exposure to high levels of H2S can very quickly lead to death. In low concentrations, it can cause headaches, fatigue, vomiting, breathing difficulties and eye irritation.
- Particulate Matter (PM). Sulphur combined with the existing humidity in the atmosphere becomes sulphur trioxide and, from there, can turn into sulphides and sulphuric acid. In aerosol form, these substances contribute to increased levels of toxic particulate matter suspended in the atmosphere, particularly fine particles (PM2.5) and ultra-fine particles (PM1). They can cause cardiovascular and respiratory diseases and are also linked to an increased incidence of cancer.
- Volatile Organic Compounds (VOCs). These are hydrocarbons that remain in a gaseous state at room temperature. They are highly volatile and abundant in the air. The oil refining industry as a whole is the world’s largest VOC emitter and controlling emissions requires a range of practices, including leak detection, preventative maintenance and regular cleaning, to ensure that these substances are not released into the atmosphere. These substances cause the smogSmog, beyond that dense fog
Smog is a mixture of air pollutantsAir pollution is one of the greatest environmental challenges of our time. The air we breathe contains various harmful substances of a chemical, physical o...
Read more that accumulate in the atmosphere, especially in urban areas. This phenomenon is character...
Read more or reddish mist that makes the air in the surrounding area unfit to breathe, and it can also cause respiratory and cardiovascular problems. Some VOCs pose extreme health risks, affecting the liver and central nervous system and even causing kidney damage or cancer.
The levels of emissions depend on several factors, including how efficient the refinery is and the type of oil being refined. In general, the most modern and efficient refineries have more optimised, cleaner systems and tend to produce less emissions than older refineries.
In addition, refineries generate emissions during the gas-burning process used to remove waste gases that cannot be recovered or recycled. However, the levels of emissions vary depending on the efficiency of the refinery and the type of gas being burned. (Sojinu, S. O., & Ejeromedoghene, O., 2019).
Main Problems Caused by Air Pollution from Refineries
Despite their importance in the global economy and the strategic resources they produce for countless sectors, oil refineries have a significant impact on the environment.
As well as requiring vast amounts of energy and natural resources, such as water, they also generate high levels of waste, some of which is toxic. Air emissions are some of the most harmful by-products of the refining process, contaminating not just the air but also soil and water.
Increased amounts of nitrous oxide (N2O) in the air combine with atmospheric moisture to produce acid rain. This, in turn, can cause extraordinary damage to ecosystems, destroying forests and acidifying both inland bodies of water and the ocean. The reduction of the pH of the water, thereby making it more acidic, alters the biodiversity that depends on marine and freshwater aquatic ecosystems. Furthermore, aquatic organisms are severely affected when polycyclic aromatic hydrocarbons are deposited in water.
The nitrogen oxides and volatile organic compounds emitted by refineries react with oxygen in the air, thereby changing levels of atmospheric ozone at ground level. Due to photochemical reactions triggered by strong solar radiation, these nitrogen oxides can lead to high concentrations of tropospheric ozoneTropospheric ozone (O3) or ground-level ozone is a gas found in the lowest layer of the Earth's atmosphere, the troposphere, which extends up to 10 kilomet...
Read more. Ground-level ozone is considered a very harmful secondary pollutant as it can affect crops, forests, plant development and associated fauna.
Similarly, greenhouse gas emissions from refineries are a significant contributor to climate change. The burning of fossil fuels in these refineries produces large amounts of carbon dioxide, one of the main greenhouse gases. In addition to CO2 emissions, refineries also emit large amounts of methane, a more potent greenhouse gas than CO2.
Net greenhouse gas emissions from refineries are a major environmental concern as they contribute to global warming and severe climate changes, in turn producing phenomena such as violent storms and hurricanes.
Reducing Emissions in the Refining Sector
Of all the activities involved in the oil industry (extraction, storage, transport and refining), refineries face the greatest challenge in terms of their net emissions. They contribute towards a reduction in air quality and have a significant impact on the environment, which, in turn, affects their ability to comply with environmental regulations designed to tackle climate change.
While crude oil refining techniques are improving all the time, the growing global demand for a wide variety of petroleum products means that compliance with environmental legislation remains a constant challenge for refineries. Legislation regulates petrochemical operations and also places stipulations on the quality of petroleum-derived products in order for them to be accepted on commercial markets.
This means that it is not just equipment and processes that need to be improved but also the way that facilities are run, including their operation, maintenance and downtime.
Therefore, it is essential to use scientific and technical processes to achieve the following:
- Optimise the use of raw materials. By improving oil refining processes, high-value products, such as petrol or diesel, can give better performance, thereby making them more efficient and cleaner to use.
- Promote energy efficiency. By capturing and using the waste heat produced, making greater use of renewable energies and incorporating innovative refining processes, the amount of energy consumed by refineries can be reduced.
- Reduce atmospheric emissionsAtmospheric emissions are pollutants emitted into the air, mainly as a result of human activities such as industry, transport by combustion vehicles and en...
Read more. The most modern refineries incorporate industrial practices and technologies that minimise the emissions produced. Such emissions are directly linked to the alteration of ecosystems and the acceleration of climate change, as well as having a chronic impact on human health. - Reduce the amount of waste generated. Waste and by-products from oil refineries are a dangerous source of pollution. As well as affecting air quality, they can also contaminate soil and water, thereby damaging ecosystems and causing serious environmental problems.
- Monitor and control emissions. Regular, real-time monitoring of emissions produced at each stage during the refining process, using devices such as Kunak sensors, allows the early detection of suspended gases and particulates that can affect air quality. This is the most effective way to optimise refining operations, identify issues quickly, such as possible gaseous leaks or process anomalies, and reduce the impact of refineries on air quality.
- Promote the use of new technologies. The oil refining sector is implementing innovative measures to promote sustainability, such as the use of technologies to safely capture and store tonnes of carbon for future use and the promotion of global decarbonisation. The oil industry is also incentivising the transition towards cleaner sources of energy, such as biofuels and green hydrogen.
The modern oil industry will face a major challenge in the coming decades to balance the economic benefits of oil with the resulting environmental damage. (Al-Rubaye, A.H., et al. 2023).
To successfully transition to a global low-emission economy and help curb climate change, it is important to have cleaner, more efficient oil refineries. (Granda, M.L., 2023) that continuously adhere to good management and business practices, are committed to sustainable development and comply with the environmental measures in force.
Sources and References
Adebiyi, F.M. (2022) – Air quality and management in petroleum refining industry: A review.
Al-Rubaye, A.H., et al. (2023) – The side effect of oil refineries on environment: as a mini review.
Damian, C. (2013) – Environmental pollution in the petroleum refining industry.
Galván Rico, L., et al. (2007). Los macroprocesos de la industria petrolera y sus consecuencias ambientales.
Granda, M.L., (2023). Análisis de las emisiones en la articulación productiva de España: determinación de sectores clave en la contaminación del medio ambiente.
Monteiro, A., et al. (2017) – Towards an improved air quality index
Sojinu, S. O., & Ejeromedoghene, O. (2019). Environmental challenges associated with processing of heavy crude oils.