Bottom Line: The City of Millbrae completed a $6 million facility at its Water Pollution Control Plant that will turn grease from local restaurants into biogas and pay for itself in 17 years.
The City of Millbrae (with the help of Chevron Energy Solutions) recently completed a new $6 million facility at its Water Pollution Control Plant that will turn inedible used kitchen grease from local restaurants into biogas -- generating renewable energy to treat the city's wastewater. Their old plant was aging and too small to support the installation and use of modern cogeneration equipment that can capture and reuse biogas. Instead of wasting a valuable energy source, the City took on the challenge of building a custom system that can be replicated anywhere.
Originally slated to take 24 months, the grease project was completed in September 2006 after 48 months. The biggest challenge, says Superintendent Joe Magner, was with the design and understanding the nature of waste water treatment.
The results of converting the facility have been the reduction of CO2 emissions by 1,178,000 pounds and production of 1.7 million kilowatt hours annually. As an added bonus, Magner discovered that the amount of biogas being produced by the system has more than doubled from 40,000 to 100,000 cubic feet of biogas per day.
The grease receiving portion had an upfront cost of $700,000 and has an ROI of 4 years. The entire $6 million project will pay for itself in 17 years. Magner stresses, however, that the ROI would be different for every facility based on digestion system, loading capacity, distance of grease receiving from digestion system, layout of treatment plant, sewage solids coming in, metals in bio solids, and many other factors.
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