CEDAR RAPIDS — After nearly 50 years burning coal, Alliant Energy’s largest Cedar Rapids unit is being converted to produce energy using natural gas.

On Wednesday, crews at Alliant Energy’s Prairie Creek Generation Station, 3300 C St. SW, worked to install the larger valves and pipes necessary to transition the station’s more than 100-megawatt No. 4 coal-burner unit to operate on a natural gas fuel source.

Justin Williams, project engineer, said the conversion began in October and should be completed by the end of the week.

“It takes a lot of upfront planning, but the idea is we bring these units down, convert them and get them up and running as quick as possible,” Williams said.

Coal-powered units use a small amount of natural gas to ignite the coal, so an infrastructure already exists to support burning natural gas, said plant engineer Katharine Manders. Converting a coal unit to 100 percent natural gas requires upgrades to the system — largely for increased gas use.

The cost for such a conversion is relatively minimal, but the effects are noticeable, said Alliant spokesman Justin Foss.

Reducing emissions

The switch is expected to reduce Prairie Creek’s carbon dioxide emissions by about 25 percent, while also cutting the plant’s sulfur dioxide, particulate matter and mercury emissions in half.

Foss said reduced emissions also should help the utility stay ahead of any potential updates to regulations handed down by the Environmental Protection Agency.

Nearby residents also may notice reduced noise pollution from the plant — namely when unit 4 kicks on.

“We’re not going to be making that noise anymore,” Foss said.

The amount of ultra-low-sulfur coal being shipped via train from Wyoming to the Cedar Rapids plant also will decrease.

Prairie Creek’s conversion is part of a larger push by Alliant Energy to phase out some of the utility’s smaller, less efficient coal-burning units through retirement or by shifting to natural gas.

Alliant Energy’s coal plant in Fox Lake, located in southern Minnesota, was retired Tuesday and the utility also has transitioned generation stations from coal to natural gas in Clinton, Dubuque and Marshalltown.

The utility’s Burlington Generation Station is expected to stop burning coal by the end of 2021 and could be switched to natural gas at that point.

By 2025 in Cedar Rapids, all four of the 245-megawatt Prairie Creek station’s coal-powered units will have been converted to burn natural gas, and Alliant’s only remaining coal-fueled units in the state will be in Lansing and Ottumwa.

In 2015, MidAmerican Energy retired two coal-fueled units in Council Bluffs and stopped using coal in the utility’s Bettendorf facility, which now burns natural gas only.

Coal Still King

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While natural gas has over the years surpassed coal as the cheaper alternative for fuel, Alliant’s growing solar and wind generation also reduces the need for those fossil fuels, Foss said.

Energy officials statewide also have touted a diverse energy grid — that is, one with multiple sources of power such as wind, solar, coal and natural gas — help reduce customer rates and increase reliability.

“The less we rely on any one form of energy, we have less of a threat of cost fluctuation,” Foss said.

According to the U.S. Energy Information Administration, coal made up about 76 percent of Iowa’s net electricity generation in 2008. That number decreased to 47 percent last year.

However, coal still is the state’s largest source of electricity generation.

Iowa ranks in the top one-third of states in coal consumption and is among the top 10 states in the nation for coal use per capita.

The state’s second biggest source of energy generation is wind, which made up 36.6 percent of Iowa’s power in 2016, according to the EIA.

l Comments: (319) 339-3175; mitchell.schmidt@thegazette.com