DEKALB, Miss. — Mississippi Power Co. says that the power plant it’s building in Kemper County has generated electricity using gas produced from coal for the first time.

Atlanta-based Southern Co., the utility’s parent company, announced that the electricity was generated during a test Wednesday. The company says it used both the part of the plant that turns soft lignite coal into a synthetic gas, as well as the chemical plant that removes carbon dioxide and other chemicals.

Mississippi Power spokesman Jeff Shepard says one of two power generating turbines was fueled with up to half synthetic gas, while continuing to burn up at least half natural gas. The plant has been generating electricity using natural gas since 2014. Shepard says the plant will continue to generate electricity normally as tests continue, using natural and synthetic gas.

The $6.8 billion plant, far over budget and behind schedule, is now supposed to be completed by Nov. 30. Mississippi Power must still start the second gasifier, synchronize the two units, and ramp up the feed of synthetic gas.

The Kemper plant is supposed to burn coal while emitting as little carbon dioxide as a typical natural gas plant.

“The technology at the heart of the first-of-its-kind facility provides a way forward for energy companies in the U.S. and around the world to cleanly generate electricity using an affordable and abundant resource,” Southern Co. Chairman and CEO Thomas Fanning said in a statement.

For now, though Shepard said the carbon dioxide was vented into the atmosphere.

“There are specifications that must be met before the carbon dioxide can be placed in the carbon dioxide pipeline and sent to oil fields for use in enhanced oil recovery,” Shepard wrote in an email.

He said ammonia and sulfuric acid, the other two byproducts from the chemical plant, were collected and stored for sale.

The plant and associated coal mine were originally supposed to cost $2.9 billion at most, and earliest estimates were lower. Customers could be asked to pay as much as $4.2 billion. In December, the Mississippi Public Service commission allowed Mississippi Power to raise rates on its 186,000 customers by $126 million a year to pay for $1.1 billion worth of equipment already generating electricity.

This story has been corrected to show that the plant has been generating power from natural gas since 2014, not 2015.