Gills Onions

When Steve Gill and his brother David agreed to process onions for their first customer in 1983, little did they realize that by 2008, they would be facing a 300,000-pound daily disposal problem of the onions’ tops, tails and peels. That is the amount of waste generated daily by the nearly 1 million pounds of onions Gills Onions processes daily. Over 10 years, Gill researched the problem and worked on solutions with the help of the ag engineering department at the University of California at Davis, HDR Inc. in Omaha, Neb., and numerous consultants.

Govern­ment grants and incentives were received when the project was verified to be running on at least 75 percent biogas. At the same time, Gill and his brother were growing the business from 19 employees in 1983 to the 400 they now employ at their 95,000-square-foot plant in Oxnard, Calif.

“We are a vertically integrated company controlling the product at every level of the operation from seed development, planting, growing, harvesting, transporting, processing and packaging up to a million pounds of onions on a daily basis,” Director of Sustainability Nikki Rodoni declares. “This is what sets us apart from our competitors and guarantees us the best quality product out there.”

The company’s previous methods of disposing of the onion waste were becoming unmanageable and cost-prohibitive. “Our previous solution was to transport the waste and disk it into the surrounding fields we farmed, which created numerous problems for the growers, such as pests and potential water contamination,” Rodoni explains. 

“It was also very expensive – about $450,000 year in labor and diesel fuel. It was becoming a deal-breaker for us to grow the business and deal with this waste issue, so we were forced to find a solution.”

Digesting Waste

Gill’s solution – known as the Advanced Energy Recovery System (AERS) – is to extract the onion juice from the solids. Approximately 30,000 gallons of juice (75 percent of the waste) per day is then diverted to an anaerobic digester manufactured by Biothane, where bacteria feeds upon it and converts it to methane and CO2. The biogas then is cleaned of sulfur so it is 100 times cleaner than natural gas and used to power two 300-kilowatt fuel cells that generate the facility’s base load of electricity.

Natural gas is blended with the biogas to power the fuel cells 24/7 depending on the level of biogas production. The fuel cells run on approximately 75 percent biogas and 25 percent natural gas. “It was all pioneered,” Co-owner Steve Gill declares. “I didn’t realize the solution I was ultimately going to come up with when I started. I just had all this waste that was growing as my business did, and I started looking at different technologies and ended up developing our own solution.” 

With the self-generation incentive program, we were able to use biogas and fuel cells to get the highest amount of money back for the process.

 

The $10.8 million system was financed by Gills Onions along with $2.7 million from the self-generation incentive program of Southern Cali­fornia Gas Co.; $3.2 million from the American Recovery and Reinvestment Act; and a $499,000 grant from the California Energy Commission for the study of sulfur removal from the biogas. The ag engineering department at the Univer­sity of California at Davis provided assistance and expertise, and helped develop the technology to produce biogas from onion waste.

“With the self-generation incentive program, we were able to use biogas and fuel cells to get the highest amount of money back for the process,” Gill explains. “That was a leap of faith on our part to take all the technology and put it into a project. It took three years to develop the juice extraction process. After we picked the two technologies – the anaerobic digester and fuel cells – we hired HDR to marry the two together, come in and do the design for the gas – to remove all the sulfur – and gas compression, and the drying and cleaning for the fuel cells.” Gill estimates the system has a five- to six-year payback.

Fuel cells were chosen because they are exempt from air pollution regulations, and they run on both biogas and natural gas, which would not have been the case for internal combustion or natural gas engines. The solids left after the onion juice is produced in the AERS process are sold for cattle feed.

Appealing Concept

Once the concept proved itself, Gill wasted no time. “Our bench scale testing was a 1-liter vessel – the bacteria was producing little bubbles in it – and the next size up for us was a 145,000-gallon anaerobic digester,” he recalls. “I didn’t want to waste any more time going through intermediate steps. Since the scientists said it would work, I took the big step of going to the next level and putting in the anaerobic digester.”

Another benefit of the onion waste disposal process – which has been operating since July 2009 – is that the farmland on which the waste used to be spread has had improved yields without it. “It was a hard project all the way to get everything done – a lot of work and dedicated people on it to help us along the way,” Gill concedes. “Looking back, it’s working fine now. It’s a great project. There were a lot of hurdles to jump in the process to get to this point. We are still making new discoveries every day – being the first of its kind, there is nothing to compare it to.”

Gills Onions now is in the permitting stage with Oxnard to install a commercial-sized battery system called a vanadium redox battery (VRB) developed by Prudent Energy Corp., Bethesda, Md. It will store electricity generated from the fuel cells during the night at the lowest demand time to discharge during the day – when rates are highest – and as backup power.

The VRB stores energy-holding electrolyte in tanks – one for positive reactions and another for negative – that are separated by a thin membrane.

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