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Fats, Oils and Grease

Fats, Oils & GreaseFats, oils and grease (FOG) refers to organic substances derived from plant and/or animal sources that are associated with food preparation.

  •    Fats are substances that are solid at room temperature.  This includes meat trimmings, butter and lard.
  •    Oils are substances that are liquid at room temperature.  This includes cooking oils, salad dressing and sauces.
  •    Grease is a mixture of fats and oils.  This includes cooked/melted fat from meat and gravy.

After exposure to high temperatures, FOG has the potential to dissolve and may enter the sewer system in a liquid form.  Upon cooling, this liquid can quickly solidify and create blockages in the pipes, which often causes sewage wastewater to back up and overflow out of manholes.  The majority of SFO’s sewage spills are the result of FOG-related blockages.

The benefits of preventing FOG from entering the sewer system:

  • Public Health - raw sewage often contains a variety of harmful bacteria and diseases.  Preventing a FOG-related sewer overflow can mitigate serious health risks.
  • Environmental - sewage overflows are hazardous to the environment, especially if they enter storm drains that flow to the Bay.  Wildlife such as fish, seabirds, and marine mammals can be adversely affected by exposure to raw sewage.
  • Financial - large overflows can be expensive to contain and cleanup.