California Air Resources Board

NATURAL GASOLINE LIQUIDS

The purpose of this advisory is to alert air pollution control districts in California of the potential for excess volatile organic compounds (VOCs) emissions occurring from natural gasoline liquids (NGL) loadout operations.

Natural gasoline liquids are those portions of reservoir gas that are liquefied at the surface in lease separators, field facilities, or gas plants. NGL's are obtained by either compression and cooling or by absorption in oil and include components such as ethane, propane, butanes, pentanes, natural gasoline, and condensate.  Although NGL is too volatile for general use, proper characteristics can be secured by futher distillation or by blending. NGL is also being used as a diluent (viscosity reducer) for oil shipped via pipeline. NGL is introduced directly from the pressurized storage tanks into the oil pipeline.

During recent inspections of gas plants and blending stations, ARB staff documented that spillage of NGL ranging between seventy milliliters to over one gallon has been occurring each time the loadout hose is disconnected from the pressurized trucks. Excess VOC emissions ranging up to eleven tons per year from these facilities have been calculated as a result of this spillage of five facilities inspected.

The ARB is requesting that local air pollution control districts, which have these type of facilities, review their new source review and organic liquid loading rules to ensure that these rules address and specifically prohibit excess drainage of NGL during truck disconnect operations, and conduct compliance inspections of these facilities.

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