On a hill overlooking the Susquehanna River, two big wind turbines crank out electricity for Kroger Co.'s Turkey Hill Dairy in rural Lancaster County, Pa., allowing it to save 25% on its power bill for the past two years.

Across the country, at a big food-distribution center Kroger also owns in Compton, Calif., a tank system installed this year uses bacteria to convert 150 tons a day of damaged produce, bread and other organic waste into a biogas that is burned on site to produce 20% of the electricity the facility uses.

...