The measure makes electricity produced from older biomass facilities, such as pulp mills, eligible for the state’s renewable energy mandate. 

Passed in 2006, I-937 requires nearly a third of the state’s utilities, those with at least 25,000 customers, to build toward getting 15 percent of their power from wind, solar, geothermal and certain woody biomass by 2020.

Supporters say Gregoire's measure will benefit rural communities and a struggling timber industry.