Ames-based Renewable Energy Group Inc. announced second-quarter net income of $23 million, a 60 percent year-over-year increase. The company sold 69.2 million gallons of biodiesel in the second quarter, a 28 percent increase from the second quarter of 2012 and its highest production quarter ever. On July 29, REG's acquisition of a 30-million gallon per year biodiesel plant from Soy Energy LLC was approved by Soy Energy unit holders. REG's plans to continue to increase biodiesel production capacity through plant acquisitions and upgrades and enhancing product margin opportunities, CEO Daniel Oh said.