Overview of EPA’s Quad O Standard

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The Environmental Protection Agency (EPA) estimates that the upstream and midstream segments of the oil and gas industry account for nearly 40 percent of volatile organic compound (VOC) emissions in the United States. As a result, the agency has proposed strict regulations on facilities that use storage vessels.

Air pollution is a serious issue for oil and gas industry professionals, so the monitoring of emissions regulations is a priority and a constant concern.

Due to a lack of regulations regarding storage vessels, the EPA proposed new standards, commonly referred to as 40 CFR 60, Subpart OOOO (Quad O), which took effect on Oct. 15, 2012, and have a one-year compliance phase.

Facilities with a Potential to Emit (PTE) of greater than six tons of VOCs yearly must install one of three approved control devices: a standard flare, an enclosed combustor, or a vapor recovery device. The standard flare must meet both 40 CFR 60.18 and Method 22A (producing no smoke from the device). The New Source Performance Standard (NSPS) in 40 CFR Part 60, Subpart Quad O, requires all combustion control devices to reduce emissions to less than six tons yearly with a 95 percent destruction and removal efficiency (DRE).

The standard also includes testing requirements. Facilities must have devices tested and retested by a third party at regular intervals, which are commonly interpreted as 180 days upon installation and startup, and within five-year intervals thereafter, or, the manufacturer provides third-party testing.

Quad O pertains to the following VOC emission sources: well completions, pneumatic controllers, equipment leaks from natural gas processing plants, sweetening units at natural gas processing plants, reciprocating compressors, centrifugal compressors, and storage vessels constructed, modified, or reconstructed after August 23, 2011.

Since state standards vary widely, Quad O will serve as the minimum, with state regulations also applicable. The rule requires that compliance at both levels be monitored.

Some Commonly Used Flaring Devices:

  • Pit flares are ground-level devices that are automatically ignited when gases are released. Pit flares are rated at an average 90 percent DRE, but exact measurements depend on wind conditions. Concerns regarding pit flares are the unknown ignition times and tremendous amounts of radiant heat. Users of pit flares also have expressed potential safety concerns for site personnel.
  • Pipe flares, referred to as shop built flares, consist of a pipe elevated above the ground with a small igniter. Pipe flares are non-enclosed, meaning the flame is not protected. Testing of pipe flares had indicated differing opinions of DRE percentages. A 2010 study, conducted by the Texas Commission of Environmental Quality, found DREs ranging as low as 40 percent due to various issues. Other studies have found DREs ranging from 70 to 80 percent – again, depending upon conditions. Pipe flares commonly have trouble staying lit, which can result in the venting of unburned hydrocarbons.
  • Enclosed combustors (e.g., Envent Thermal Oxidizer) are engineered to burn gases with high efficiency and low emissions. Because thermal oxidizers are enclosed, ignition is protected. This protects against gas venting due to environmental and performance factors. Enclosed combustors operate at an average of >99 percent – verified by third party EPA source testing.

The EPA eventually is expected to increase the required DRE level from today’s 95 percent to an even more stringent Best Available Control Technolgy (BACT) which is >99%.

(Brian Miller is Envent Corporation’s Director of HES. If you have any questions, please contact him at brian.miller@envent.net or (888) 997-9465)