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APRIL 2008
SHORT REPORT

SEEING THROUGH THE FOG
By: Michael Romico

Fats, oils and grease may be a nuisance to most operators, but to some municipalities FOG is liquid gold.

It's well known that FOG collected from grease interceptors can be used to fuel waste water treatment plants. A biogas called methane is produced when bacteria metabolize the organic solids found in FOG, and this biogas can be collected, compressed and used to power combustion engines.

California is well on its way to perfecting the process of using FOG this way. Last year the City of Rialto became the latest municipality to adopt a FOG-to-methane plan to fuel its waste water treatment plant.

Thanks to an agreement with Chevron Energy Solutions, a subsidiary of Chevron Corp., the Rialto plan will rely on a 900kW fuel-cell power plant designed to generate electricity using methane. FOG-receiving stations will be set up so haulers can route FOG to the fuel-cell plant instead of moving it to landfills. In addition, the residual waste heat from the fuel cells will be put to work to warm the FOG digesters and thus stimulate further methane production.

Seeing Through The FOG
Whether outdoors or in, your grease interceptors keep fats, oils and grease out of your local sewer lines. Here's how you can help them do their job better, thanks in part to the NRA FOG Tool Kit.

If you haven't given thought to your grease interceptors lately, now's the time to pay more attention. A new wave of regulations on the handling of fats, oils and grease, plus rising interest in best environmental practices, is shining a spotlight on how to handle FOG.

The good news is there's a document available to help understand how best to manage FOG. In late 2006 the National Restaurant Association released the FOG Tool Kit, the first guide of its kind to explain grease control terms and technical guidelines.

The NRA commissioned the guide after realizing that state and local authorities had begun taking different paths on FOG regulation, says Christine Andrews, NRA's director of health and safety regulatory affairs based in Washington, D.C. "With so many local FOG ordinances coming up across the nation," Andrews says, "we needed to provide an educational tool for our state restaurant association partners as well as our membership."

Andrews says the tool kit was assembled with input from an array of experts from across the country. "We have since worked individually at the state level with our state partners to address the specific concerns or challenges they may have in their local jurisdictions."

The Devil's In The Greasy Details
One key component of the NRA's Tool Kit is the cleaning of grease interceptors, of which there are two general types: tanks installed outside that need to be pumped out by a professional service, and indoor units that typically reside in the kitchen under a sink. The indoor units usually are cleaned and maintained by the kitchen staff.

The FOG Tool Kit advises operators to have outdoor units pumped when the accumulation of floating grease and settled solids exceeds 25% of the interceptor's capacity, says John Shaffer, president of Environmental Engineering and Contracting in Santa Ana, Calif., and a contributor to the FOG Tool Kit. The "25% rule," Shaffer says, can be better than setting standard maintenance intervals because the amount of FOG produced by one type of operation will be different from others in the same municipality. (Think of the difference in FOG output between a steakhouse and a sandwich shop.)

Of course, store employees are not involved in the maintenance of outdoor grease interceptors. That task falls to pumping contractors who usually work at night to pump out tanks. The challenge, though, can be to understand how well that maintenance is being done. Shaffer recommends that unit managers inspect their interceptors when they are being pumped out and not rely solely on grease haulers to schedule maintenance

Stopping Grease Before It Escapes
Indoor grease interceptors are becoming more popular in certain locations for two reasons. First, many urban sites don't offer the physical space needed for a traditional outdoor tank. And second, indoor units typically are more cost-effective than installing outdoor tanks.

Among the under-the-counter interceptors, hydromechanical units are the most straightforward, says Shaffer. These consist of a small tank with inlet and outlet pipes that temporarily captures the water and grease before discharging it. Gravity separates liquid FOG to the top while solids settle to the bottom. With no moving parts, this type of interceptor is reliable and simple to use if it is cleaned on a regular basis. These units also perform better if there is a strainer basket installed ahead of the unit to screen out solids.

To clean, you open the lid and skim floating fats and oils. To clear the solids, you can empty the strainer basket or use a water pump similar to those found in hardware stores to remove the water and then scoop out the solids. The greasy waste and solids can be disposed with other refuse, while the water can be returned to the interceptor. Shaffer says cleaning the unit is not complicated and costs little, but few relish the task. "It's a very messy job," he says.

A fairly new option for indoor units is a grease removal device, or GRD, that adds an auto-skimming feature to help collect top-floating fats and oils. Shaffer says many GRDs, which are becoming more popular, feature easy-to-remove baskets for quick solids disposal. GRDs require less cleaning than hydromechanical interceptors. But generally, because GRDs have moving parts, these units do need more frequent maintenance to keep them operating efficiently.

To download a copy of the full FOG Tool Kit, you can visit one of several state restaurant association Web sites that offer it online, including this site for the Georgia Restaurant Association: www.garestaurants.org/FOG%20ToolKit.pdf.

The Human Factor
Ultimately, grease interceptors rely on diligent kitchen managers and well-trained employees to work properly. "The whole key to grease interceptor performance is maintenance, maintenance, maintenance"

Shaffer says. "It doesn't matter how well-designed the unit is. If you don't clean or maintain it properly, it's not going to work." Shaffer says the FOG Tool Kit includes best practices every restaurant should follow, including:

  • Limit the amount of grease disposed in drains.  Yellow grease should be collected and rendered.
  • Scrape plates and utensils of grease and oils before washing.
  • Use drain screens to keep unnecessary grease out of drain lines.
  • When grease spills, use absorbent materials, such as paper towels or kitty litter, to clean first. Resist the urge to use water to flush these spills into the drain.
  • Eliminate or limit the amount of greasy foods poured into garbage disposals.
  • Train employees in all procedures.

That last point, says Shaffer, remains a vital part of the process. "An inherent challenge in restaurants is the turnover of employees and managers," he says. When a new manager takes control, he or she may not be aware of the location of the grease interceptor, much less its cleaning or maintenance cycle.

Thus, says Shaffer, all restaurant managers should examine their outdoor interceptors and use employee maintenance sign-in checklists for indoor units to ensure consistent interceptor maintenance.

Turning FOG Into Fuel
Fats, oils and grease may be a nuisance to most operators, but for some cities FOG is liquid gold.

You've probably heard that FOG collected from grease interceptors is being used in some parts of the country to power wastewater treatment plants. This is possible because a biogas called methane is produced when bacteria metabolize the organic solids found in FOG, and this biogas can be collected, compressed and used to power combustion engines.

California is well on its way to perfecting the process of using FOG this way. Last year the City of Rialto, for example, became the latest municipality to adopt a FOG-to-methane plan to fuel its wastewater treatment plant.

Thanks to an agreement with Chevron Energy Solutions, a subsidiary of Chevron Corp., Rialto's wastewater plant will rely on a 900kW fuel-cell power plant designed to generate electricity using methane. FOG-receiving stations will be set up so haulers can route FOG to the fuel-cell plant instead of moving it to landfills. In addition, the residual waste heat from the fuel cells will be put to work to warm the FOG digesters and thus stimulate further methane production.

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