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Fats, Oils, and Grease



If FOG didn’t exist already, someone with a thirst for random destruction would have invented it. Hardened globs of fat, oil and grease can clog your pipes, cause flooding, produce weapons-grade odor in your lift stations, and gum up your plant equipment.

In order to defeat FOG, it helps to understand the full scope of the problem. Here are a few fast facts about FOG.

Creation by Saponification 

The oils and fats that are discharged from restaurants, manufacturing plants and homes aren’t necessarily a problem on their own. These fatty acids are non-polar molecules that are derived from meat, vegetable oils, dairy products and more. You’ve heard oil and water don’t mix, and it’s true – they usually cannot combine with water, which is considered a polar molecule, because of their chemical makeup and difference in density.


These fatty acids are non-polar molecules that are derived from meat, vegetable oils, dairy products and more.

A chemical decomposition process called hydrolysis changes that dynamic. The fatty acids can become free fatty acids (FFA) and glycerols when they’re heated up during cooking, such as when you use oil to fry food. Hydrolysis can also occur in the sewer pipe. In the pipe, the FFAs will interact with calcium in another chemical process known as saponification. This combination of FFAs and calcium in the pipes results in a solid substance that will stick to the walls of the pipes and slow down your water flow, or even worse, stop the flow completely and cause an SSO.

These hardened deposits might look like stalactites, such as what you might see hanging in a cave. Researchers for North Carolina State University, who are worldwide experts in FOG, found that they are comprised of calcium-based fatty acid salts – like soap.

“FOG itself cannot create these deposits,” says Dr. Joel Ducoste, a professor of civil, construction and environmental engineering at NC State. “The FOG must first be broken down into its constituent parts: glycerol and free fatty acids. These free fatty acids – specifically, saturated fatty acids – can react with calcium in the sewage collection system to form the hardened deposits.”




-Dr. Joel Ducoste, Professor, NC State University

Why You Need to Fear Fatbergs

Once the FOG hardens, it can turn into what’s known as a fatberg. These freakish, iceberg-like masses have drawn intense curiosity from media and the public. Part of one was turned into a museum piece in Michigan.

Huge fatbergs are a real problem, though, causing blockages and floods worldwide. They’re very time-consuming and expensive to remove – it cost $100,000 to extract the 100-foot, 19-ton Michigan fatberg, for example. And the collateral damage can be an environmental and PR nightmare: One Maryland municipal water company reported that more than 10,000 gallons of untreated sewage leaked into a creek because of a fatberg blockage in 2021.




The fatbergs start as FOG, but grow into gigantic, pipe-blocking masses when wipes and other personal care items flushed by residents latch onto them . The pandemic has caused people to use – and flush – more wipes than ever before, which makes it even more important to prevent FOG buildup.




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You Can’t Depend on Grease Traps and Enforcement Programs

Blockages – often triggered by FOG – cause 23,000 to 75,000 sanitary sewer overflows per year , according to the EPA . Many of them are started by discharges from restaurants and other businesses.

You might think tough municipal laws that require businesses to install and regularly clean grease traps would forestall much of that problem. There are a couple problems with that theory:




Businesses might not invest in the right grease interceptor (GI) equipment and, even if they do, they might not clean it regularly, which could cause outflows to the system. North Carolina State researchers noted that “the rules of GI maintenance and management vary significantly in terms of grease and solids storage capacity and operational experiences” and that while most establishments clean their traps every two to three months, once per month is much more effective at limiting long chain fatty acid outflows.



Cities often don’t have nearly enough staff to keep up with regular inspections to make sure businesses are following grease trap regulations.

The financial shockwaves brought on by the coronavirus pandemic have made it even less likely this plan will be successful, as restaurants struggle to get back on their feet and municipalities face larger deficits because of increased costs and revenue shortfalls.


Then, there’s politics. For example, one California city tried to enforce its grease trap policy  but members of the city council overruled staff and gave a few businesses a break on their penalties.

That’s why it’s not enough to just hope FOG won’t collect in your pipes … or only spring into action when fatbergs show up in your system … or think the local government rules and regulations will stop all discharges. 

Taking a wait and see approach is costly. Cities spend about $25 billion each year to remove FOG deposits and deal with the blockage effects of an SSO7. With the average cost per hour to run a typical vacuum truck at about $200-300/hour (not including the cost of the truck itself), that adds up to a LOT of municipalities playing a constant game of whack-a-mole. A smarter strategy is to take stock of the blockage problems in your system and find the best way to prevent them without deploying your trucks and crew all over the city chasing after FOG.



The Science

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Click here to learn more about our solutions for FOG

The Solution

The Terror of the Treatment System
FOG Facts Contact
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