Chemical Engineering

FOG Separation Technology Expands to New Application Areas

Fats, oil and grease (FOG) waste can create environmental problems for water-treatment and sewage systems, but can be a potential resource if collected and separated efficiently. A technology originally developed by Downey Ridge Environmental Co. (Lansing, W.Va.; to separate FOG from water for disposal of grease-trap waste is now finding uses in other industry sectors, such as biodiesel production, food processing, anaerobic digestion and water reclamation. The thermal separation technology, known as Greasezilla®, helps generate useful products and fuels from FOG waste.

The process begins by gravity separation of water and FOG-containing sludge. The sludge is then pumped into dual insulated tanks that are heated to a constant temperature of 160°F for 24 hours to thermally render the fats in the sludge and bring them out of solution. The heating separates the tank contents into three distinct layers: brown grease, a mixture of mostly saturated triglycerides in the C16 to C18 range; pasteurized organic material; and residual water.

A portion (~5%) of the brown grease recovered from the system is used directly as fuel to power its own boiler, while the rest can be sold as a feedstock for making biodiesel, because of its low moisture level (<1%).

The FOG separation system is being used upstream of municipal water treatment facilities, as well as by biodiesel producers, who can generate their own feedstock by processing FOG waste that waste haulers pay to unload, explains company president Ron Crosier. Large food-processing facilities are now beginning to use the modular system to process their own FOG waste, rather than paying for disposal. In addition, the pasteurized sludge layer is used in anaerobic digesters to generate biogas.

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