Renewable Energy Group Inc.'s $125 million public offering of 2.75 percent senior secured notes will close June 3, the company said today. Ames-based REG has granted underwriters a 13-day option to purchase up to an additional $18.75 million aggregate principal amount of such notes to cover possible overallotments. The company will pay interest semiannually at a rate of 2.75 percent per year. The notes cannot be redeemed before they mature in 2019. They will be convertible at an initial rate of about $13.26 per share. REG intends to use approximately $100 million of the net proceeds from this offering to replace the letter of credit that guarantees bonds issued in connection with its acquisition of the Dynamic Fuels LLC biorefinery in Geismar, La., or to redeem those bonds.