Tops and tails are becoming much more than garbage at Gills Onions, an onion processor in Oxnard, Calif. Today marks the unveiling of the company's onion-powered electrical system, a first-of-its-kind initiative to turn onion waste into energy.
 
"This whole project is about eliminating our onion waste," explained Steven Gill, an owner/partner of Gills Onions. "This has been a long-term project for us for the last 10 years."
The anaerobic digester.
The anaerobic digester.

Every day, Gills Onions -- which sells diced, sliced, slivered and puréed onions to wholesale and retail customers -- generates about 300,000 pounds of onion waste -- the company loses about 35 percent of the onion to "tops, tails and skins," Gill said.

In the past, the company has dealt with the waste by sending it out to fields, spreading it out to decompose and return to the soil naturally. But that method eventually became too much of a problem: The cost and effort involved in finding enough fields to spread the onion discards on, and the insect life that was attracted to the waste, became more hassle than it was worth.

Enter "the AERS." Gills' Advanced Energy Recovery System takes all that waste and turns it into two kinds of energy: electricity and calories (in the form of cattle feed. Depending on how thinly you slice it, the project, which was unveiled today at Gills facility in Oxnard, Calif., is likely the first such project in the world (although if you know of any other onion-waste-to-energy projects, I'd love to hear about them).
How Gills Onions' waste-to-power process works Click for a full-sized chart.
chart

Here's how AERS works: the onion waste goes in, it's shredded and pressed to squeeze all the juice out of the onions, which reduces the solid waste by 75 percent. The juice goes into the anaerobic digester, where microbes turn the juice into methane gas. The gas then goes to fuel cells, which is converted into electricity.

And 300,000 pounds of onions makes a lot of electricity: 600 kilowatts per day, enough to run 35 to 40 percent of the electricity used by Gills' facility.
This is what 70,000 gallons of onion juice looks like.
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The remaining 25 percent of the onion waste after the juice is squeezed is pulp, which is used as cattle feed. Steven Gill said the daily diet of cattle feed sells on the market for about enough to cover the cost of delivery.

But the juice-to-energy system saves much more; Gills expects to save $700,000 worth of electricity a year, and $400,000 a year in waste disposal costs.

In all, the project cost $9.5 million to implement, but Gills received $2.7 million in incentives for the project from Southern California Gas Company, as part of California's Self-Generation Incentive Program. As a result, the project will pay for itself in an estimated six years, although Gill himself said he expects it will pay for itself in less time.

Once this project is underway -- and Gill said it hasn't been much of a challenge to learn how to turn onion juice into energy -- the company has more plans. The next step is to explore ways that the water can be recycled after the onion juice has gone through the anaerobic digester, instead of being discharged into city sewers.

And Gill said some of his neighbors have also expressed interest in this kind of project; a carrot producer and a winery were two examples he offered.
onion juice