Gills Onions Advanced Energy Recovery System
HDR worked with Gills Onions to take its Advanced Energy Recovery System from an energy-saving concept to a breakthrough $9.5 million system.
This system will change how food processing waste is treated through a sustainable process—a process that is expected to pay for itself in less than six years—while reducing the onion processing plant operational carbon footprint.
Gills Onions, the largest fresh-cut onion processor in the nation, faced a growing problem with disposal of waste from their onion processing plant. To solve this problem, Gills Onions hired HDR as the lead engineering firm.
This problem was turned into a positive with an innovative facility that greatly reduces the volume of waste and uses the waste to produce power and cattle feed. In the facility, juice is extracted from onion peels and treated in a high-rate anaerobic reactor to produce methane-rich biogas. The biogas is then treated to remove moisture and sulfur and used to power two 300 kilowatt fuel cells which supply 60 percent of the onion processor's annual power needs. As a result, the owner has achieved increased energy independence, elimination of a waste stream, reduced operational cost and a smaller carbon footprint.
In April 2010, this project was awarded the prestigious Grand Conceptor Award from the American Council of Engineering Companies, the first HDR project in history to win the award for best overall engineering achievement.
The treatment facility includes a system to grind and dewater more than 200,000 pounds per day of onion peels to reduce waste by 75 percent. This was achieved using two stages of grinding and pressing to produce 30,000 gallons per day of onion juice and 20 tons per day of onion cake.
The cake is hauled to the California Central Valley as cattle feed. The juice, with more than 60,000 mg/L of COD, is digested in a high-rate upflow anaerobic sludge blanket reactor (UASB) supplied by Biothane from Camden, N.J. The 100 cfm of methane-rich biogas generated in the reactor is treated to remove moisture and sulfur compounds and used to feed two 300 kW fuel cells by Fuel Cell Energy from Danbury, Conn.
Fuel cells were selected over other more conventional combined heat and power generation systems due to their lower atmospheric emissions and reduced carbon footprint. The 0.6 MW of electricity generated continuously supplies more than 80 percent of the Gills Onions processing facility base load. The heat required to maintain the UASB at 95°F is recovered from an existing 850 HP natural gas engine driving an air compressor. Heat from the fuel cell exhaust gases will be recovered in a new process the project team is currently developing.
HDR provided civil, mechanical, and process engineering, and was instrumental in selecting equipment, negotiating contracts with suppliers, and assisting during construction and start-up. HDR performed process integration, allowing juice production, anaerobic digestion, gas treatment with emergency gas flaring, clean power generation, and heat recovery to work together. Overall project management and coordination was by Deaton and Associates, from Saint George, Utah. The construction firm was Hartigan/Foley from Ventura. Calif. Electrical design was by Calkins Electric from Camarillo, Calif; and structural design by Vinci and Associates, from Westlake Village, Calif.
The project has received nationwide attention for innovative technology and renewable energy production. Sempra Energy awarded Gills Onions $2.7 million as part of the renewable energy Self Generation Incentive Program, and the company expects to receive $3 million in investment tax credits from the Federal Government for the use of fuel cells operated with biogas.
The project was delivered on time, and the ribbon-cutting ceremony was held on July 17, 2009. The plant has been fully operational since then.
- 2010 - Grand Conceptor Award, American Council of Engineering Companies
- 2010 - Golden State Award, American Council of Engineering Companies, California Chapter