After 56 years of burning coal at its Lake Julian power plant, Duke Energy has officially shut down the coal operation.

"At 4 p.m. on Jan. 29, 2020, Duke Energy achieved a significant milestone and officially shut down the 344-megawatt Asheville coal plant in Arden, North Carolina," Duke Energy spokeswoman Heather Danenhower said. "The coal plant reliably served customers since 1964. Some demolition work has already started and is expected to be completed in 2023."

The Lake Julian plant consumed huge amounts of coal. In 2018, a Duke spokesperson said its units 1 and 2 consumed approximately 4,032 tons of coal per day when operating at full capacity.

4,000 rail cars a year of coal

In May 2019, Danenhower noted, "The Asheville coal-fired units will burn approximately 400,000 tons of coal this year. That’s about 4,000 rail cars."

More: Answer Man: Does Duke Energy smokestack pollute or is it just steam?

The plan to switch over to natural gas has been in the works for years, and Duke completed the 560-megawatt combined-cycle natural gas plant in late 2019. The $893 million natural gas plant was built on Duke's nearly 700-acre campus near Lake Julian.

"Duke Energy customers in both North Carolina and South Carolina are now receiving 460 megawatts of cleaner-burning, highly efficient energy from the new Asheville Combined Cycle Station," Danenhower said. "We will add 100 more megawatts to the new natural gas power plant — for a total of 560 megawatts — when we bring the remaining steam turbine generator online in the first quarter of 2020."

Julie Mayfield, co-director of the Asheville environmental advocacy nonprofit MountainTrue, said the closure of the coal facility is cause for celebration, but natural gas, while a much cleaner fuel, also comes with some burdens.

"The closure of this plant is the long-awaited result of tremendous community advocacy in Asheville and Buncombe County," Mayfield said. "This was the outcome we sought as part of the Asheville Beyond Coal Campaign that launched back in 2012."

The closure of the coal plant and opening of the gas-fired facility also "represents an immediate improvement in terms of local environmental impact.

"We will no longer have coal ash being produced there, and carbon emissions will be cut virtually in half," Mayfield said. "Other air pollutants will be reduced significantly, and the water in Lake Julian can return to normal mountain temperatures, rather than being the warmest lake in the entire state."

Duke has removed much of the coal ash from the Lake Julian site, trucking it to Asheville Regional Airport for a fill project and to a storage facility in Georgia. But the utility also has petitioned the N.C. Department of Environmental Quality for a permit to build an industrial landfill on the plant site in Skyland to store some coal ash.

Natural gas has environmental issues, too

Natural gas requires no post-use storage, and it burns considerably cleaner than coal. But it's not without environmental impacts.

"The transition to natural gas does not address the larger concern around global carbon pollution and greenhouse gas emissions from fracking, and we recognize those are significant issues that do need to be addressed," said Mayfield, who also is a member of Asheville City Council and a candidate for the state legislature in the 49th Senate District. "We certainly support the efforts locally, regionally, nationally and internationally to reduce greenhouse gas emissions."

Duke is also moving forward with plans to build a solar energy facility on site.

More: Answer Man: Lake Julian smokestack coming down? County manager dual role?

"We have earmarked $120 million for renewables in the area, including building a solar plant and battery-storage facility at the Asheville station," Danenhower said, adding that investments in natural gas and renewables will allow the utility to "retire coal plants faster and help the company achieve its goal of cutting carbon dioxide emissions by half by 2030."

The utility had previously heavily invested in the coal plant, putting in place a "scrubber smokestack" and other upgrades that cost about $300 million, in response to new emissions rules the North Carolina General Assembly passed in 2002 that required emissions reductions at 14 coal-fired plants. Some of the scrubber stack equipment still has resale value, as it's not that old, Duke said previously.