Fugitive emissions

Fugitive emissions

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Fugitive emissions are emissions of gases or vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....

s from pressurized equipment due to leak
A leak is a hole or other opening, usually unintended and therefore undesired, in a container or fluid-containing system, such as a tank or a ship's hull, through which the contents of the container can escape or outside matter can enter the container...

s and various other unintended or irregular releases of gases, mostly from industrial activities. As well as the economic cost of lost commodities, fugitive emissions contribute to air pollution
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

 and climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

. A detailed inventory of greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

 emissions from upstream oil and gas
Petroleum industry
The petroleum industry includes the global processes of exploration, extraction, refining, transporting , and marketing petroleum products. The largest volume products of the industry are fuel oil and gasoline...

 activities in Canada for the year 2000 estimated that fugitive equipment leaks had a global warming potential
Global warming potential
Global-warming potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time...

 equivalent to the release of 17 million metric tonnes of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, or 12 per cent of all greenhouse gases emitted by the sector. Venting of natural gas, flaring
Gas flare
A gas flare, alternatively known as a flare stack, is an elevated vertical conveyance found accompanying the presence of oil wells, gas wells, rigs, refineries, chemical plants, natural gas plants, and landfills....

, accidental releases and storage losses accounted for an additional 38 per cent.

Fugitive emissions present other risks and hazards. Emissions of volatile organic compounds such as benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

 from oil refineries
A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value.-Types of refineries:Different types of refineries are as follows:...

 and chemical plant
Chemical plant
A chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transformation and or separation of materials. Chemical plants use special equipment,...

s pose a long term health risk to workers and local communities. In situations where large amounts of flammable liquids and gases are contained under pressure, leaks also increase the risk of fire and explosion.

Leaks from pressurized process equipment generally occur through valves, pipe connections, mechanical seals
Seal (mechanical)
A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage , containing pressure, or excluding contamination...

, or related equipment. Fugitive emissions also occur at evaporative sources such as waste water treatment ponds and storage tanks. Because of the large number of potential leak sources at large facilities and the difficulties in detecting and repairing some leaks, fugitive emissions can be a significant proportion of total emissions. Even though the quantities of leaked gases may be small, leaks of gases that have serious health or environmental impacts can cause a significant problem.

To minimize and control leaks at process facilities operators carry out regular leak detection and repair activities. Routine inspections of process equipment with gas detector
Gas detector
A gas detector is a device which detects the presence of various gases within an area, usually as part of a safety system. This type of equipment is used to detect a gas leak and interface with a control system so a process can be automatically shut down...

s can be used to identify leaks and estimate the leak rate in order to decide on appropriate corrective action. Proper routine maintenance of equipment reduces the likelihood of leaks.

Because of the technical difficulties and costs of detecting and quantifying actual fugitive emissions at a site or facility, and the variability and intermittent nature of emission flow rates, bottom-up estimates based on standard emission factor
Emission factor
An emission intensity is the average emission rate of a given pollutant from a given source relative to the intensity of a specific activity; for example grams of carbon dioxide released per megajoule of energy produced, or the ratio of greenhouse gas emissions produced to GDP...

s are generally used for annual reporting purposes.

New technologies are under development that could revolutionize the detection and monitoring of fugitive emissions. One technology, known as differential absorption light detection and ranging (DIAL), can be used to remotely measure concentration profiles of hydrocarbons in the atmosphere up to several hundred meters from a facility. DIAL has been used for refinery surveys in Europe for over 15 years. A pilot study carried out in 2005 using DIAL found that actual emissions at a refinery were fifteen times higher than those previously reported using the emission factor approach. The fugitive emissions were equivalent to 0.17% of the refinery throughput.

Portable gas leak imaging cameras are also a new technology that can be used to improve leak detection and repair, leading to reduced fugitive emissions. The cameras use infrared imaging technology to produce video images in which invisible gases escaping from leak sources can be clearly identified.

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