By Naureen Malik.
(Bloomberg) -- As green groups pressure the natural gas industry to clean up its act, an alternative to the fossil fuel is emerging in some unlikely places: pig farms and sewers.
Duke Energy Corp., one of the largest U.S. utilities, began generating power in March for its North Carolina customers using “renewable” natural gas created by capturing methane from the waste produced by 62,000 hogs. National Grid Plc, meanwhile, is set to open a plant that will process gas from wastewater to serve New York customers. Overall in 2018, 26 renewable natural gas plants will open in the U.S., bringing the total to 92.