Renewable Energy Group Inc. broke ground Tuesday on a $13.2 million improvement project at its Newton biodiesel refinery, the Ames-based company announced.

The project will increase the plant's ability to produce biodiesel of even higher purity from a wider array of raw materials. "This investment shows our continuing confidence in biodiesel for the long term," said Daniel Oh, REG's president and CEO.  The company refinanced its original loan through a banking syndicate led by AgStar Financial Services to extend the term and help pay for the project.

The refinancing provides for an additional $5 million to fund the capital project and extends the maturity date by five years. The upgraded process, including distillation, removes impurities and leaves behind the purest form of the fuel.