ROCKVILLE, Md. (AP) — Emergent BioSolutions Inc. said Wednesday it will receive a $30 million payment from the federal government as part of an existing contract for the anthrax vaccine BioThrax. The payment is based on the Food and Drug Administration’s approval to extend the vaccine’s shelf life to four years from three years. Emergent’s contract with the U.S. government calls for supplying more than 14 million doses of the vaccine into 2011. It is part of a program to stockpile BioThrax and other vaccines for defense against a potential chemical attack. Emergent expects to recognize the $30 million payment in its second-quarter financial results. The total contract is worth about $405 million.