How Is Restaurant Grease & Oil Recycled?

In 2022, Americans consumed approximately 11.5 metric tons of soybean oil, 2.9 metric tons of rapeseed oil, and 1.7 metric tons of palm oil. In addition to that, there were also high consumption rates of coconut, olive, sunflower seed, cottonseed, and peanut oils. While some of this consumption happened at home, a lot more happened in restaurants.

It’s estimated that restaurants produce an average of 35 pounds of used grease and oil each day. By the end of a month, that’s around 1,050 pounds of used oil that must be recycled. You can’t just pour it down the drain. Doing so risks oily clogs that block your own and your community’s sewer pipes. It can lead to sewage backups that could lead to your kitchen being shut down. Can you afford that loss of business?

Oregon Plumbing Specialty Code requires you to install grease traps in your restaurant or kitchen when it’s a new construction, remodeling, change of ownership, or redevelopment. If you don’t have a grease trap, you may very likely need one. The goal is to keep fats, oils, and grease (FOG) from the sewer lines, which means connecting dishwashers, sinks, floor drains, cooking equipment, and garbage disposals to a grease interceptor. If you do have one, have you ever stopped to think about what happens to the FOG in your grease trap?

What Happens in a Grease Trap?

There are three types of grease traps: automatic, gravity, and manual. Smaller restaurants are most likely to use manual (passive) grease traps due to the cost and variety of sizes. They are usually made from stainless steel or plastic and require regular draining and cleaning.

Automatic systems are more expensive, but they’re efficient and require less maintenance. The automatic system removes FOG automatically and transfers it to a collection bin. For restaurant owners who want less to do, it’s the best choice, even if it has a higher upfront price point.

Gravity grease traps are less likely to be located in a restaurant because the tanks are installed in-ground. They have a higher capacity, however, which makes them useful in kitchens that get a lot of traffic, such as a hospital or university kitchen.

No matter which grease trap you have, the basic process is that the water from sinks, dishwashers, floor drains, etc. goes to the inlet pipe that leads to the tank. This tank has one or two sections. Food particles sink to the bottom of the tank while the FOG rises to the top. The water trapped between the food sediment and fat layers moves through another pipe to the sewer lines or into the secondary tank where the process repeats itself.

Any remaining fats in the secondary tank rise to the top and food particles sink to the bottom. The wastewater trapped between them goes to the outlet pipe that leads to the sewers. Once the FOG and food waste layers have built up, they must be emptied and cleaned. Covers at the top of the tanks can be removed to suction out the FOG and food solids. 

Cleaning schedules may be weekly for some restaurants or every couple of weeks. It depends on the restaurant’s menu. Restaurants that make fried dishes will fill a grease trap faster than someone who only grills food. Fast food restaurants go through a lot of oil every week.

The difference with an automated grease trap is that heating elements warm the layer of FOG and skimmers move it from the top of the wastewater. It’s pumped to a FOG container that needs to be emptied periodically. It doesn’t require cleaning as often as a manual trap.

This process is usually completed by a grease trap cleaning and inspection specialist. In fact, restaurant owners need to keep records of when their grease trap was cleaned and inspected, so make sure you partner with a company that is licensed and provides you with a FOG report before the technicians leave. You need a copy of that FOG report!

You’re also going to have used cooking oil in fryers that cannot be poured down the drain. A used cooking oil storage container is provided to restaurants who sign up for Northwest Biofuel’s cooking oil collection service. Transfer your cooking oil to that container that you keep outside or in an indoor container, depending on your restaurant’s storage space.

Where Does the FOG Go?

When it’s time to have your grease trap cleaned and your cooking oil container emptied, what happens to the used cooking oil and fats? It’s pumped into a collection truck and hauled away. From there, it’s processed and converted into other products. Your used cooking oil stays out of the sewers and isn’t going to block your inlets or outlet pipes.

The FOG is transported to a processing facility where it undergoes filtration to remove any debris like bread crumbs, batter pieces, meats, and vegetable scraps. The filtered oil is heated to get rid of any water, bacteria, and other pathogens. Once this process is done and the used cooking oil is in a clean, refined form, the next stage of processing starts. 

Transesterification is the process where used cooking oil is converted to biodiesel. The used cooking oil is mixed with a catalyst like sodium hydroxide or potassium glycerol and a short-chain alcohol like methanol to start the chemical conversion.

Once the chemical conversion completes, the resulting products are glycerin and methyl ester. Glycerin can be used to make soaps and other cosmetic products like moisturizers and perfumes. The methyl ester is a biodiesel product that can be blended with diesel to reduce dependency on petroleum-based diesel. 

It cannot be used on its own as the processed oil can create engine deposits that degrade engine life. The processed biodiesel is always mixed with other diesel for that reason. Biodiesel benefits the environment as it ignites faster and generates less pollution by reducing hydrocarbons, sulfur dioxide, and even carbon monoxide emissions.

Take Care of Your Grease Traps

Ask Northwest Biofuel about grease trap cleaning services for restaurants or commercial kitchens in Portland, Oregon, Portland’s metropolitan areas, and Southwest Washington. We do not require you to agree to a long-term contract and provide 24/7 emergency service.

When you have your grease trap cleaned and inspected with us, you may qualify for discounts if you recycle your used cooking oil with us. Plus, there’s a $25 account credit available if you leave a key so that we can clean out your grease trap outside of your business hours. 

If you find your FOG is building up faster than our scheduled arrival, call us and we’ll send an employee to collect your used cooking oils within 24 hours. Our goal is to ensure you’re completely satisfied with our grease trap and used cooking oil service.

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