EcoRenovator - Kroger's anaerobic digester, 13 million kWh/year

I found this link over on Builditsolar. Really interesting article and some pretty great power output here! It doesn't mention cost, but ROI seems pretty good.

A powerful use for spoiled food - Los Angeles Times

Quote:

Several chest-high trash bins containing a feast of limp waffles, wilting flowers, bruised mangoes and plastic-wrapped steak sat in an airy space laced with piping. Stores send food unable to be donated or sold to the facility, where it is dumped into a massive grinder — cardboard and plastic packaging included.

After being pulverized, the mass is sent to a pulping machine, which filters out inorganic materials such as glass and metal and mixes in hot wastewater from a nearby dairy creamery to create a sludgy substance.

...

From there, the mulch is piped into a 250,000-gallon staging tank before being steadily fed into a 2-million-gallon silo. The contraption essentially functions as a multi-story stomach.

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.