Food scraps from restaurants and hotels were added in 2004. The plant now processes 100 to 200 tons of food scraps a week. The goal is to do 100 to 200 tons a day enough to power the equivalent of 1,300 to 2,600 homes and rapid expansion is now expected. By the end of next year, the district expects to create so much power from non-traditional waste that it'll be able to sell excess power to Pacific Gas & Electric, a local electricity supplier, Williams says.

If 50% of the USA's food waste went through a similar process as the one here, there'd be enough power for 2.5 million homes a year, the EPA says.

The food-scrap project "hasn't been a cakewalk," Williams says.

Waste haulers, who pay the utility district to take the waste, collect the food scraps from restaurants and hotels as part of their normal garbage pickups.

Some of the haulers weed out big items, such as cardboard boxes used for produce. Other haulers have restaurants and grocers do more of the separation so that the waste is cleaner.

Upon arrival via truck at the plant, the food scraps look like mounds of wet dirt. They're dumped into 20,000-gallon underground tanks. There, grinders turn the scraps into a mud-like substance. Bigger items, such as rocks and utensils, fall out.

On a recent morning, it took just minutes for a 20-ton truck to unload. Pressure pulls most of the odors into the tank. Still, the smell of cheese was present.

"That all comes from last night's dinner plates," Williams said as he watched.

From the underground tanks, the waste is run through sieves that reject plastics, bottle caps and other small items.

Then, the waste goes into anaerobic "digesters," 2 million-gallon tanks filled with bacteria.