Honolulu’s Department of Environmental Services says a $300 million project to expand the city’s waste-to-energy plant is halfway finished.

The city is adding a third boiler and making other improvements to its H-POWER plant at Campbell Industrial Park, which burns waste to generate electricity. H-POWER currently generates enough electrical energy to power 50,000 homes. By the time the expansion is completed the middle of next year, the plant will be capable of powering 75,000 homes. It will also supply eight percent of the electricity consumed on Oahu. Construction on the expansion began last year. The city said Thursday workers expect to complete all mechanical work, including on the boiler and steam turbine generator, over the coming year.