Ames-based Renewable Energy Group has announced plans to expand its biodiesel refinery in Geismar, La., by 250 million gallons annually to 340 million gallons per year. According to a news release, construction should begin in mid- to late 2021, with completion scheduled in late 2023. The expansion represents a capital investment of about $825 million. It received tax and workforce incentives from the state of Louisiana. REG’s Geismar plant was the first renewable biodiesel plant in the country, and was acquired by REG in 2014, the release stated. President and CEO Cynthia Warner said the expansion marks an “exciting milestone” for the company.” “We are developing this project with our proprietary process technology, and are proud to continue to deliver sustainable fuel solutions to our customers and accelerate the transition to cleaner energy,” Warner said in the release.