OMAHA, Neb., Aug 31, 2011 (BUSINESS WIRE) -- Gavilon, LLC, a leading commodity management firm serving the agriculture and energy industries, and the third largest grain operation in the United States, today announced it has entered into a multiservice commercial agreement with Heron Lake BioEnergy, LLC, a dry mill ethanol facility located in Heron Lake, Minnesota. Under the terms of the agreement, Gavilon will be the ethanol plant's exclusive corn supplier, and ethanol and distillers dried grai