Waste Management Inc. has shifted its investment in a waste gasification venture to an equity holding in its partner.

Waste Management exchanged its equity interest in S4Energy Solutions LLC, a joint venture with InEnTec Inc., for an equity position with InEnTec. The two companies are developing a waste gasification plan in Arlington, Ore., using InEnTec’s plasma enhanced melter (PEM) technology. The companies formed S4 in 2009.

Construction of the Arlington plant was recently completed, and the Oregon Department of Environmental Quality has issued all the permits necessary for the facility to begin operations, Waste Management said in a news release. The operation will begin as a 25 ton per day commercial demonstration plant.

“Changing our investment from a joint venture development into an equity position with InEnTec is more consistent with the company’s other portfolio investments,” said Joe Vaillancourt, managing director for Waste Management’s Organic Growth Group. “We are commited to the advancement of the PEM technology.”

“We are delighted that Waste Management has expressed its confidence in InEnTec by becoming one of our largest shareholders,” said Karl Schoene, president and chief executive officer of InEnTec.

In the PEM process, waste materials are fed into a closed chamber where they are superheated to temperatures of between 10,000 and 20,000 degrees Fahrenheit using the electricity-conducting gas plasma. The intense heat of the process rearranges the molecular structure of the waste, transforming organic (carbon-based) materials into an ultra-clean, synthesis gas (syngas). The clean syngas then can be converted to transportation fuels such as ethanol and diesel, industrial products like hydrogen and methanol or used as a substitute for natural gas for heating or electricity generation.