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SoCal Ralphs and Food 4 Less Turn Veggie Waste into Energy

composting_tomatoes.jpg
Photo caption: composting tomatoes. The French Laundry garden, Yountville, CA - 10.11.09. Photo by urbanfoodie33 via Flickr.
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There's no doubt that a lot of food goes to waste here in America. And restaurants aren't the only guilty parties. Grocery stores have plenty of items that are disposed of after their due date, and it's not easy to get rid of them either. They're driven off in giant diesel-fueled trucks (hello, carbon footprint!) to be disposed of. But the folks at Kroger Co. in Southern California have found a way to eliminate that step and actually create energy in the process.

Kroger, the company who runs Ralphs and Food 4 Less grocery stores, uses a machine called an anaerobic digester at their Compton facility, which takes grocery store waste and turns it into electricity that powers their stores.

It's really a pretty amazing machine. Basically all of the waste -- from dead flowers to old meat -- are put into a giant vat with some hot water that's been pumped off of a nearby dairy plant. Then it's moved into 250,000-gallon staging tank before being steadily fed into a 2-million-gallon silo.

Says the Times:

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Inside, devoid of oxygen, bacteria munch away on the liquid refuse, naturally converting it into methane gas. The gas, which floats to the top of the tank, is siphoned out to power three on-site turbine engines. The 13 million kilowatt-hours of electricity they produce per year could power more than 2,000 California homes over the period, according to Kroger.

Excess water from the digester is pumped out, purified and sent into the industrial sewer. Leftover sludge becomes nutrient-rich organic fertilizer, enough to nourish 8,000 acres of soil.

The folks at Kroger won't say exactly how much they spent on the machine, which reduces their waste by 150 tons a day. But they project that over its lifetime, it will have saved them $110 million.