ROLLING, Wisconsin — A 95-year-old sawmill business in northeastern Wisconsin can now generate enough power from burning bark and wood chips that it has started selling excess electricity back to the grid. In fact, if Kretz Lumber Co., Inc. wasn’t using its new system to power the operations at the sawmill, it could support an estimated 225 to 240 homes, according to president Troy Brown. Kretz Lumber is an employee-owned business made up of about 85 people. …The boiler system started up in June. It burns byproducts from the sawmill to create heat, through steam lines, for the lumber dry kilns, Brown said. The equipment is fueled by “woody biomass,” Brown said. …The company received a total of $1.5 million from state and federal grants, including from the Wood Innovations Grant, Energy Innovation Grant Program and Wisconsin’s Focus on Energy.