By Karen Uhlenhuth, Midwest Energy News.

This summer, one of the country's largest producers of biogas from animal manure is expected to begin operations in northwest Missouri.

It's a large-scale example of technology that has been slow to take off in the United States, but new federal policy may be changing that.

In 2013, St. Louis-based Roeslein Alternative Energy reached an agreement with pork giant Smithfield Foods to build and operate a system to capture and purify methane from the manure produced by about two million pigs. Smithfield's confinement barns comprise one of the largest hog-feeding facilities in the country, according to Roeslein.