Grease traps are one of the most popular FOG (fats, oils and grease) management solutions, with passive (manual) and automatic traps being the most popular options for commercial kitchen operators looking to prevent grease related issues.
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They both do essentially the same job of separating FOG from wastewater though at a glance, automatic grease traps seem very expensive compared to manual grease traps, there are more factors to consider than just the initial cost of the unit.
This article will compare the two system types, explaining the main differences and the pros and cons of each system so you can make an informed buying decision and select the right system for your requirements.
Firstly, lets cover what each system does so you can understand what to expect from each type of unit.
Traditional passive grease traps simply slow the flow of wastewater to allow it to cool and separate into 3 layers; FOG, solids and clear water. The FOG forms a “grease mat” at the top of the unit and solids either accumulate at the bottom of the unit or collect inside a strainer which is located just after the inlet. The clear water escapes via the outlet.
Automatic systems, also known as AGRU’s (automatic grease removal units), perform many of the same operations as a manual grease trap. Much like a manual system the flow of wastewater is slowed to allow it to cool and separate though automatic systems almost always feature the addition of a removable strainer basket for solids collection. This means the wastewater inside the unit will mainly contain FOG with only small amounts of solid waste escaping the strainer and settling at the bottom of the unit.
The similarities between the automatic and passive models stop once the FOG separates and rises to the top inside the unit. Rather than letting the FOG form a “grease mat”, automatic system re-heat and skim out the FOG automatically on a programmed schedule. The skimmed FOG is then transferred into a collector bin for easy removal and recycling.
So now you know what each system does, lets delve into some comparison between the 2 systems, which may help with your buying decision. The 4 main area’s covered are:
There is a direct correlation between how efficient a grease trap is and the amount of grease inside the system. The more kilograms of grease inside the unit, the less efficient the trap becomes, which impacts overall performance.
For this reason, manual grease traps are less efficient than automatic ones as the grease accumulates inside them until its either pumped out or emptied manually. As automatic traps skim and remove FOG on a scheduled basis, grease doesn’t build-up inside the unit meaning the system will maintain maximum efficiency and perform at a consistent level.
The graphs below give a visual representation of performance vs kilograms of grease based on 25kg traps connected to equipment producing 2.5kg of grease per day:
As you can see the overall performance of the manual trap drops quickly once the amount of grease gets to a certain level, while the automatic trap maintains consistent performance.
Both systems are kind to the environment as they help prevent FOG entering the sewerage system but what happens to the recovered and pumped out waste?
With manual traps, the grease management service company who pump out the trap will dispose of all substances removed from the trap. The grease will often be recycled into biodiesel and any solids will be disposed of in the correct manner, helping to keep our environment clean.
Automatic traps remove grease and deposit it into a container in liquid form. This can then be collected along with other used cooking and waste oil by your relevant service provider. Potentially, if enough is produced, the removed grease from automatic traps can be sold as an additional revenue stream.
So, while both systems are eco-friendly, automatic traps edge ahead due to the potential of adding an extra source of income via selling removed grease.
Purchase price is usually the deciding factor between choosing a manual or automatic grease trap, however there are other costs which need to be considered when buying any type of grease trap. All the costs to consider are:
The purchase cost of an automatic grease trap can be 5 times more than the purchase cost of its manual equivalent. Manual traps also have no moving parts meaning they need no daily maintenance and require no electricity to run, unlike automatic traps which need around 10 minutes of maintenance a day and require an electricity supply to function.
It looks like manual traps come out on top but the final consideration of pump out costs swing the comparison in the favour of automatic grease traps. Manual traps require pumping out every 2-4 weeks at a cost of between £150 and £200, whereas automatic traps only require pumping out every 3-6 months at the same cost. While you can increase the time between pump outs of manual traps to up to 8 weeks by adding a biological grease treatment fluid into the system or “dosing”, this adds to the purchase / install costs and to running costs. So, over the course of 3 years, automatic traps will be much cheaper overall.
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Let’s compare 2 similar automatic and manual Grease Guardian grease traps, the GGX15 (automatic) and GT1 (manual), so you can see which one will cost you less over a 3-year period.
The figures below are based on the following:
Evidently, in the first year the GGX15 automatic unit works out more expensive than the manual GT1, mainly due to the high purchase price. However, by the end of year 2, the much higher pump out costs of the manual unit mean the overall cost is higher its automatic counterpart. After 3 years, the cost difference between the 2 units is nearly £3,000 in favour of the automatic GGX15. If you also add potential income from selling recovered oil from the automatic unit, the cost difference increases even more.
Although automatic grease traps require a higher initial investment, the additional features gained by the extra investment offer increased performance, potential for additional revenue and reduced long term costs, making automatic grease removal units the best choice for grease management.
If you own a restaurant or other business within the foodservice industry, chances are good you’re already using some sort of grease interceptor. If not, sooner or later you’ll likely face clogged pipes, back-ups into your kitchen and costly fines.
In the United States, there are three types of grease interceptors generally found within the foodservice industry: small passive hydromechanical grease interceptors (sometimes referred to as grease traps), larger grease interceptors made out of plastic, fiberglass, steel or concrete, and automatic grease removal devices. Though using any of these options is better than nothing, all grease traps are not created equally and, as technology improves, so do grease interceptors.
Today, many establishments are choosing point-source interceptors, like our Big Dipper® Automatic Grease and Oils Removal System, to meet their pretreatment needs. Here are a few reasons why:
Point-source interceptors are the go-to option for a wide range of foodservice establishments, from full-service restaurants to school cafeterias, to maintain compliance with local sewer system fats, oil and grease (FOG) discharge limits.
Our Big Dipper® system is also a popular option for existing establishments that need to revamp their pretreatment procedures to meet updated regulations. The above-ground system is easy to install and doesn’t require major plumbing changes.
Grease may look innocent in its just-cooked, liquid form. But, the fact is, it can wreak havoc on your plumbing and sewer lines once it cools. Grease and food particle buildup within a building’s plumbing system is a leading contributor to line blockages in the U.S. and abroad.
These blockages can seriously jeopardize normal operations and create health and safety hazards within the facility. Proper installation of a point-source interceptor, like our Big Dipper®, can reduce or eliminate grease problems altogether.
Point-source interceptors can be easily cleaned and emptied by employees, without a pump truck or special equipment, which eliminates the cost of hiring a contractor.
Replacement costs are also a factor. Traditional cast concrete grease interceptors break down as the years go by, and often need to be replaced after 8 or 10 years. In some places, our innovative Big Dippers have been operating for two to three times as long.
Even with a high-capacity interceptor, like our Trapzilla®, already in place, a point-source interceptor is the perfect addition. The point-source placement cuts down on the amount of fats, oil and grease that enter your pipes, which, in turn, cuts down on the amount of grease your trap collects.
Perhaps more important, though, is this also helps prevent build-up and blockages in your plumbing. These blockages can reduce the lifespan of your pipes, and lead to messy, costly blockages and back-ups. A grease interceptor can prevent those emergency calls to a plumber.
For large food service establishments, such as hospital cafeterias, college dining halls or resort hotel kitchens, this can be vital. These kinds of establishments often have significant indoor plumbing that wastewater may travel through before it gets to the grease trap or the local public sewer system.
The Big Dipper® Automatic Grease Removal Device automatically runs, based on pre-set skim times and frequencies. Grease that accumulates in the grease interceptor can be disposed of in a municipally approved waste container.
Grease traps and grease interceptors are not one-size fits all devices. It’s important to understand your individual requirements and restraints, and make the best choice based on those.
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