25 Michigan coal plants are set to retire by 2020

Michigan's long love affair with coal is on the wane.

Coal-fired power plants have for years supplied over 50% of the state's electricity generation. Now that figure is poised for a big drop.

Due to old age and tighter environmental regulations, 25 coal units at Michigan power plants are scheduled to shut down by 2020.

Industry experts expect the state to make up that lost capacity by importing power from its regional grid and through greater natural gas power generation and more renewable energy from wind turbines and solar panels. Gov. Rick Snyder also has pushed for increased energy efficiency.

The shift away from coal power should significantly cut Michigan's emissions of carbon dioxide, the most prevalent greenhouse gas associated with global warming. Last year coal generated just over 50% of electricity in Michigan, compared to 39% of total U.S. energy generation.

Electricity made from natural gas produces 50% to 60% less carbon than than that of coal, although scientific studies suggest those benefits are less if the natural gas extraction process results in significant methane leakage. Methane is a more potent greenhouse gas than carbon dioxide, but its lifetime in the atmosphere is much shorter.

The planned coal unit retirements predate the Obama administration's August unveiling of the first-ever nationwide regulations for carbon dioxide emissions from power plants.

Under the controversial Clean Power Plan, Michigan must reduce its carbon emissions rate 39% by 2030 from its 2012 level. Michigan is already on track for a 17% reduction by 2020, according to EPA data.

Mothballing those 25 coal-burning units will help Michigan reach the goal. Nine of those units are owned by Consumers Energy or DTE Energy; the rest belong to either publicly-owned power entities or private companies.

State officials are to submit a detailed plan in September 2016 on how exactly Michigan will comply with the new regulations.

The state's largest utility company, Consumers Energy, says it will have retired seven of its oldest coal plants and coal units by next April, representing about 30% of its total generating capacity. The average age of the plants is 60 years, said Consumers Energy spokesman Dan Bishop.

The utility will make up about half of that lost capacity through its purchase of what was a privately-owned natural gas-fired power plant in Jackson, the former DPC Juniper plant. The remaining gap will be filled through short-term contracts to buy out-of-state electricity on the regional grid.

Consumers Energy plans to invest about $2 billion in upgrades to its five newer coal plants to ensure future compliance with the new carbon federal regulations. "Our plan is to keep operating those facilities," Bishop said.

DTE recently closed its coal plant in Harbor Beach and previously retired a Marysville plant. By next April, it plans to shutter two units at its Trenton Channel coal plant. That will leave DTE with about 15 coal units in operation, said Skiles Boyd, the utility's vice president of environmental management and resources.

But most of those will likely disappear in the next 15 years, as "there is no piece of control equipment we can put on to meet carbon rules under the Clean Power Plan...there really isn't anything economical to collect carbon," Boyd said.

"So by 2030, our rough scenario is probably only Monroe will be remaining," Boyd said, referring to DTE's coal-fired Monroe Power Plant.

DTE is replacing some of that lost coal capacity with natural gas plants it purchased in Carson City and East China Township.

The 25 Michigan coal-fired power units that are retiring: