Bob Walker, the founder Bixby Energy Systems, a nearly bankrupt alternative energy firm that once promised to revolutionize the coal industry, is facing "a significant number" of new criminal charges in a forthcoming indictment.

Walker, 69, of Ramsey, was indicted in December in connection with an alleged investment fraud scheme involving Bixby stock. Federal prosecutors in Minneapolis filed a motion Friday seeking a 90-day delay in that case because they said they expect a "superseding" indictment will require additional time for legal motions.

Peter Wold, Walker's attorney, agrees with the motion, according to Assistant U.S. Attorney Christopher Wilton, the prosecutor in the case.

Walker is best-known as the inventor of Sleep Number beds. After leaving Sleep Comfort in the mid-1990s, he went on to Bixby, which sold high-efficiency stoves that burn corn pellets. The firm is named for Bixby, Minn., a town where Walker, a North Dakota native, traveled while developing the stove in northern Minnesota.

Under Walker's leadership, Bixby switched in 2008 to marketing an invention that converts coal into clean-burning natural gas. He and several associates raised funds in an effort to produce commercial units for sale in China, but the company has struggled to get them to work. Bixby has reported substantial losses.

Walker faces up to five years in prison on the current indictment. He said he is innocent of any wrongdoing.

Dan Browning • 612-673-4493