Onion producer uses waste for energy

By Lisa Gibson
Posted July 29, 2009, at 4:08 p.m. CST

Oxnard, Calif.,-based Gills Onions, a fresh onion producer, will soon be able to achieve 100 percent of its electricity requirement, 600 kilowatts daily, through anaerobic digestion of its onion waste.

The company's Advanced Energy Recovery System will convert 75 percent of the 300,000 pounds of waste produced daily into biogas to be fed into two 300-kilowatt fuel cells, according to the company. In the process, the onion waste will be transported from inside the plant directly through a mechanical juice extraction process, where 75 percent will be expressed as onion juice and the remaining 25 percent compressed for cattle feed. The juice will be equalized in a 70,000-gallon holding tank and fed at a constant rate into the 145,000-gallon bioreactor where anaerobic digestion produces biogas, according to Gills Onions. The biogas will then flow into a conditioning process which will purify, dehumidify and compress it so it's acceptable for use in the fuel cells. The fuel cells are up and running and the entire system should be operational in about two weeks, according to Nikki Rodoni, sustainability coordinator for Gills Onions, adding that the project is expected to be a success. "Our results and testing have been coming back better than expected," she said.

The $9.5 million project will save the company $700,000 in electricity costs and $400,000 in diesel fuel for tractors and spreaders and for labor, transportation and land application of the onion waste. When the company was first established 25 years ago, all the waste was hauled to the fields, spread and disked in to the soil. Later, it was chopped at the plant before being hauled to the fields and more recently, the company chopped and processed 75 percent of the waste into juice that was taken to the fields and 25 percent into cattle feed, according to the company.

Gills Onions received a $499,000 grant from the California Energy Commission for AERS and a $1.8 million investment tax credit, according to the company. Additionally, the company will be eligible to receive $2.7 million from Southern California Gas Co. as part of a state program to encourage self-contained electricity generation by businesses.