Rentech Inc. on Tuesday said it plans to exercise its option to acquire additional equity in fellow biofuel technology developer ClearFuels Technology Inc. in order to become the majority shareholder.

The Los Angeles developer of bio-based synthetic fuels for jetliners and other uses plans to merge one of its subsidiaries into ClearFuels, with ClearFuels as the surviving company. Existing ClearFuels investors would retain a minority interest in the merged company. Financial terms were not disclosed.

Rentech acquired a 25 percent stake in ClearFuels, a renewable biofuels company in Aiea, Hawaii, in June 2009, and signed the option agreement last September. It has assumed control of the two companies’ joint integrated bio-refinery project in Hawaii, which is being funded in part by a $23 million grant from the U.S. Energy Department.

Later this year the gasifier will be integrated with Rentech’s Product Demonstration Unit to produce certified renewable synthetic jet and diesel fuels from feedstocks such as bagasse, which is the fibrous matter remaining after sugarcane or sorghum stalks are crushed to extract their juice.

“We now add the ClearFuels biomass gasifier to our suite of energy conversion technologies, which includes the Rentech-SilvaGas biomass gasifier and Rentech’s process to produce drop-in fuels from synthetic gas,” Chief Executive D. Hunt Ramsbottom said in a statement. “Rentech can offer multiple integrated systems to convert a wide variety of cellulosic materials into renewable low-carbon fuels certified for commercial aviation and ground vehicles.”

Rentech also is building plant in Rialto designed to convert urban green waste such as yard clippings into fuels, with a projected start date of late 2012.

Rentech shares closed down 1 cent, or less than a percent, to $1.14 on the New York Alternet.