Helena Joyce
Gas flares, also known as flare stacks, flare booms, ground flares, or flare pits, are gas combustion devices used in places such as petroleum refineries, chemical plants, and natural gas processing plants. Flares emit various pollutants, including carbon dioxide (CO2), methane (CH4), black carbon (soot), nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO), and volatile organic compounds (VOCs). The combustion and pollutant removal efficiencies of flares can be less than 90%, and the pollution from flare exhaust is often underestimated. EPA estimates that there are about 500 flares at over 100 US refineries, but there are many more at chemical plants and drilling sites. Remote sensing studies have shown that these sources release significantly more pollution than what is reported to state and federal regulators.
| Characteristics | Values |
|---|---|
| Flares emit | CO2, CH4, black carbon (soot), nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO), volatile organic compounds (VOCs), aromatic hydrocarbons (benzene, toluene, xylenes), benzo(a)pyrene, acetaldehyde, ozone precursors, endocrine disrupting chemicals, nitrous oxide, hydrogen sulfide (H2S) |
| Flares are used in | Petroleum refineries, chemical plants, natural gas processing plants, oil or gas extraction sites, landfills |
| Flares are used for | Burning off flammable gas, safety, emergency purposes, disposal of unwanted associated petroleum gas, depressurizing equipment, burning excess gas |
| Flares are a source of | Air pollution, greenhouse gas emissions, climate pollution, odor pollution |
| Flares are monitored by | EPA |
| Number of flares | 500 at over 100 U.S. refineries |
| Flares release | 400 million tons of CO2e emissions per year |
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What You'll Learn
Carbon dioxide and methane emissions
Gas flaring is a 160-year-old oil industry practice of burning associated gas, a common byproduct of oil extraction. Flares are gas combustion devices used in petroleum refineries, chemical plants, natural gas processing plants, and oil and gas extraction sites. Gas flares are used for burning off flammable gas released by safety valves during unplanned overpressuring of plant equipment. They are also used for the planned combustion of gases over short periods during plant startups and shutdowns.
Gas flaring produces carbon dioxide (CO2) and methane (CH4), among other compounds, depending on the chemical composition of the natural gas and how well it burns in the flare. The amount of carbon dioxide and methane emitted depends on the flare's efficiency. Flares with low efficiency release more methane into the atmosphere. Flares in landfills, for example, have a combustion efficiency of less than 90%.
Methane is a potent greenhouse gas with a global warming potential around 28 times greater than carbon dioxide on a 100-year basis. However, according to the Intergovernmental Panel on Climate Change, methane is over 80 times more powerful than carbon dioxide as a warming gas on a 20-year timeframe. Therefore, while flaring converts methane to carbon dioxide, a less harmful greenhouse gas, it still contributes significantly to global warming.
In the United States, more than 20,000 flares in the oil and natural gas supply chains emit an estimated 20-21 million metric tons of CO2e per year, accounting for 9% of the greenhouse gas emissions from the oil and gas sector. Globally, flaring releases about 400 million tons of CO2e emissions annually, with emissions from flaring contributing 270 Mt of CO2 in 2017.
To reduce carbon dioxide and methane emissions from flaring, governments and industries have pledged to eliminate or reduce flaring. The World Bank's Zero Routine Flaring by 2030 (ZRF) initiative, for example, commits governments and oil companies to end routine flaring as soon as possible and no later than 2030. The Global Methane Pledge, signed by 111 nations at COP26, also aims to reduce methane emissions by at least 30% from 2020 levels by 2030.
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Carcinogens and ozone precursors
Flares emit a range of hazardous pollutants, including carcinogens and ozone precursors. Flares are commonly used in municipal solid waste landfills, and the pollution from flare exhaust is often underestimated.
Ozone precursors, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs), are gases that react in the atmosphere to form ground-level ozone, also known as smog. This occurs when NOx and VOCs come into contact with sunlight, triggering a reaction that creates ozone. Ground-level ozone is a significant health hazard, causing respiratory issues such as asthma and reduced lung function, and it can even lead to premature death.
The combustion of fossil fuels, including gasoline, oil, and coal, in power plants, motor vehicles, and industrial processes, is a primary source of NOx emissions. VOCs, on the other hand, are released from various sources, including consumer products like paint, household chemicals, motor vehicles, refineries, and chemical plants.
Flares themselves contribute to the emission of ozone precursors. Studies have shown that landfill flares emit hazardous pollutants, including NOx and VOCs, which can form ozone. Additionally, the combustion of a mixture of propylene and natural gas in flares can result in the incomplete combustion and release of pollutants such as acetaldehyde.
The impact of flare emissions on ozone precursor concentrations can vary depending on spatial and temporal factors. For example, FV emissions (emissions from flaring and venting) have a more significant impact on NO2 concentrations in areas with FV emissions, while reductions in NO2 levels may be observed in downwind regions.
Furthermore, the Environmental Integrity Project has highlighted the underestimation of emissions from flares by industries. Remote sensing studies have revealed that refineries and other sources release significantly more pollution than what is reported to regulators, indicating that flare emissions may be contributing more to ozone precursor levels than currently understood.
Overall, flares emit carcinogens and ozone precursors that have significant health and environmental implications. The formation of ground-level ozone from these precursors contributes to air pollution and poses risks to human health, particularly for individuals with pre-existing respiratory conditions.
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Greenhouse gases
Flares are a major source of greenhouse gas emissions. Gas flaring, or the burning of natural gas associated with oil extraction, has persisted since the beginning of oil production over 160 years ago. While it is a relatively safe method of disposing of excess gas, it is also wasteful and polluting. Flares emit various greenhouse gases, including carbon dioxide (CO2), methane (CH4), and nitrous oxide.
Each year, flaring releases about 400 million tons of CO2 emissions, which is a significant contributor to global warming and climate change. The methane emissions from flaring are particularly concerning, as methane is a potent greenhouse gas with a global warming potential around 28 times greater than carbon dioxide over a 100-year period. According to the Intergovernmental Panel on Climate Change, methane is over 80 times more powerful than carbon dioxide as a warming gas on a 20-year timeframe. This means that the annual CO2 emissions from flaring are increased by around 80 million tons.
In addition to the direct emissions from flaring, there are also indirect emissions associated with the practice. For example, the gas that is flared could be put to good use and potentially displace more polluting fuels such as coal and diesel, which have higher emissions per energy unit. By wasting this gas, the opportunity to reduce emissions from other sources is lost.
Flaring is a significant contributor to greenhouse gas emissions globally, and it is concentrated in a limited set of countries. Russia flares the most, followed by the United States, which has historically been ranked near the top after Russia, Iraq, and Iran. Flaring reduction could play a crucial role in meeting country-specific greenhouse gas reduction targets under the Paris Agreement. For example, Yemen, Algeria, and Iraq could fully meet their NDC targets through gas flaring reductions, while several other countries could meet a substantial portion of their targets by reducing flaring.
Flares are also commonly used in municipal solid waste landfills, and these flares emit greenhouse gases such as methane and nitrous oxide. While flares can be useful for odor and greenhouse gas control in landfills, they can also be a potential source of hazardous pollutants and greenhouse gases if they are not operating properly. Overall, flaring is a significant source of greenhouse gas emissions that contributes to global warming and climate change. Reducing flaring and utilizing the gas for productive purposes is essential to mitigate these emissions and meet international climate targets.
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Respiratory health risks
Flares emit various pollutants that can have detrimental effects on respiratory health. The specific respiratory health risks associated with flare emissions include:
Increased respiratory diseases: Flaring activities have been linked to a rise in respiratory health issues. Studies have found that emissions from flares can cause an increase in respiratory diseases due to black carbon particle exposure. For example, research in North Dakota showed that a 1% increase in flared natural gas led to a 0.73% rise in respiratory-related hospital visits. Similarly, investigations in industrial facilities and anaerobic digestion plants have confirmed the health risks of flare emissions, with reports of respiratory hospital visits in North Dakota attributed to flaring.
Asthma flare-ups: Flares emit pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx) that can trigger asthma symptoms. The exposure to these pollutants can lead to asthma attacks and exacerbate existing asthma conditions. The impact of flares on asthma is significant, with estimates suggesting that O&G production in the U.S. contributes to 410,000 asthma exacerbations annually.
Irritation of airways: Nitrogen dioxide (NO2), a common pollutant emitted from flares, is known to irritate airways and aggravate respiratory diseases. High levels of NO2 can cause breathing problems and trigger asthma symptoms.
Lung function and disease: Ground-level ozone (O3), formed from reactions with pollutants like VOCs and NOx, poses significant risks to respiratory health. Exposure to ozone can reduce lung function and lead to lung disease. Additionally, long-term exposure to air pollution, including pollutants from flares, has been linked to lung cancer.
Cardiovascular and cerebrovascular issues: Particulate matter (PM) pollution, which includes pollutants with diameters of less than 10 and 2.5 microns (PM10 and PM2.5), can penetrate deep into the lungs and enter the bloodstream. This can result in cardiovascular issues such as ischaemic heart disease and cerebrovascular problems like strokes.
The respiratory health risks associated with flare emissions highlight the importance of reducing air pollution and transitioning to cleaner energy sources to protect public health.
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Black carbon
Gas flaring is the burning of natural gas associated with oil extraction. Flares are also used to rapidly depressurize equipment and manage pressure variations by burning excess gas. Gas flaring is a significant source of atmospheric pollutants, including black carbon (BC).
Research suggests that gas flaring may contribute about 40% of the annual black carbon deposits in the Arctic. However, the contribution of gas flaring to black carbon emissions has often been neglected or underestimated in emission inventories and models. This is partly due to the assumption that flaring produces a smokeless flame. Factors such as fuel gas composition and combustion characteristics strongly influence the amount and nature of black carbon produced, and these factors vary across different flares and regions.
To address the issue of black carbon emissions from gas flaring, improvements in flare gas recovery systems and economic or political incentives for companies to reduce flaring have been proposed. Reducing black carbon emissions through emission control measures would have immediate benefits for air quality and global warming.
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Frequently asked questions
Flares emit carbon dioxide (CO2), methane (CH4), black carbon (soot), nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO), and various volatile organic compounds (VOCs).
The release of these pollutants contributes to global warming and climate change. For example, methane is over 80 times more powerful than carbon dioxide as a warming gas in the short to medium term. VOCs form smog, contribute to respiratory ailments, and include carcinogens like benzene. Black carbon deposits are believed to accelerate the melting of snow and ice in the Arctic.
To reduce pollution from flares, regulatory action and stronger standards from environmental agencies such as the EPA and BLM are necessary. Additionally, improving flare efficiency and addressing routine flaring through maintenance and operational standards can help reduce emissions. Capturing and utilizing associated gases, such as through power generation, is another way to reduce flaring and its environmental impact.
