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October 14, 2005
FRESNO, Ca. - A dedication and ribbon cutting ceremony was held today for the recently completed Wastewater Pre-Treatment and Renewable Energy Anaerobic Digester Facility. A.J. Yates, Undersecretary of the California Department of Food and Agriculture, attended and speaking to the invited guests, cited the need for innovation and technology as a means to solve the current and future problems faced by California agriculture. Mike Dages, Fresno City Council President, also addressed the attendees and, as did all project participants, thanked Valley Fig Growers for their foresight in developing such an environmentally sound project. Mr. Dages praised their commitment to the city and, specifically, southeast Fresno.
Mike Emigh, President of Valley Fig Growers stated, “This $1.6 million wastewater pre-treatment system, started in August 2004, has already begun to yield lower costs through the anaerobic digestion of sugars and organic waste solids in the processing wastewater stream. This system will free up capacity for the rapidly growing Fresno residential needs, enough for 2,500 new homes. Not only will this project help the bottom line of our grower/members, but the community at large benefits.”
The system consists of an anaerobic digester (covered, lined lagoon), micro-turbine electrical generator, heat exchangers, and related equipment. The largest element of the system, the anaerobic digester, works like a septic system. Microbes use enzymes that turn carbohydrates into simple sugars, amino acids and fatty acids. Other microbes convert the simple sugars to acetic acid. A third group of microbes produce methane and carbon dioxide from the acetic acid.
The gas is captured and used as fuel for a methane burning, 70kw micro-turbine electrical generator. The electricity generated will be used in plant operations. George Wiltsee of Ingersoll-Rand Energy Systems, the micro-turbine supplier, said "Valley Fig Growers has adopted an innovative technology that can help solve the environmental challenges associated with the availability of clean water and energy. "
A portion of the funding was provided by a grant from the State of California Energy Commission Public Interest Energy Research (PIER) Grant Program. The $476,000 grant was one of five awarded in 2002 under PIER Renewable Energy Program Area - Targeted Biomass Solicitation for Biogas Systems or Anaerobic Digestion Technologies in California. Prior to the award, Valley Fig Growers spent nearly two years looking for a solution to the high cost of wastewater disposal. The award of the PIER grant made the solution cost effective.
Provost & Pritchard Engineering Group Inc wrote the grant proposal and designed the system. According to Donald Ikemiya, Division Director of Natural Resources for P&P, "We’ve created a project whose wastewater pretreatment and renewable energy benefits will not only showcase the feasibility of this project, but also motivate other food processors to step up to the challenge of addressing high wastewater disposal costs and high energy costs and doing so in an environmentally friendly manner."
Russell J. Murray and Associates assisted in the design, and then managed construction and startup operations. Russ Murray said, “The successful completion and startup of the Valley Fig anaerobic digester is a great example of waste water being used to produce renewable energy, in addition to reducing disposal costs. Other food processors and dairy farmers need to explore this technology as natural gas and electricity costs continue to climb. The digestion of waste can also help solve many of the environmental issues facing these industries.”
Statistics
- Figs and raisins processed annually – 8,500 tons
- Gallons of effluent generated per day – 40,000 gallons on a 7 day per week basis
- BOD – 4,500 ppm
- TSS – 900 ppm
- Area of digester lagoon – 26,500 square feet or .6 acres
- Capacity of digester lagoon – 1.8 million gallons
- Retention time – 45 days Initial gas production – 2,000 to 2,500 cubic feet per hour
- Expected reduction in BOD and TSS 70 to 90%
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