Iowa-based Renewable Energy Group Inc. has completed its acquisition of Syntroleum Corp., which owns half of a biofuels refinery in Geismar.

Renewable Energy Group and Syntroleum signed a purchase agreement in December, but Syntroleum’s shareholders had to give their approval. They did so on Tuesday. Under the deal, Syntroleum shareholders will receive nearly 3.5 million shares of REG stock, which closed Tuesday at $9.97.

Renewable Energy Group subsidiary REG Synthetic Fuels LLC will be the owner of Syntroleum’s half of the Dynamic Fuels LLC plant in Geismar. The biorefinery can produce up to 75 million gallons of renewable diesel a year from animal and waste fat. But the facility has not operated since late 2012, when it shut down for maintenance. Syntroleum was reluctant to invest the $10 million needed to restart the facility.

In late May, Renewable Energy Group announced it would buy the other half of the refinery, owned by Tyson Foods Inc., in a deal worth up to $65 million.

Renewable Energy Group President and Chief Executive Officer Daniel J. Oh said the Syntroleum acquisition includes advanced biofuels technologies, including an intellectual property portfolio with 186 patents issued or pending.

Headquartered in Ames, Iowa, REG owns and operates nine active biorefineries in five states and distributes biodiesel through a national network of distribution terminals.