Car production isn't the greenest of processes, but in recent decades many automakers have at least made attempts to reduce environmental impact -- and General Motors is the latest to take a step towards improving it.

The automaker has announced a $24 million investment in the use of landfill gas at its Indiana and Michigan assembly plants.

10 Highlights From The Detroit Auto Show

GM says the new equipment has the capacity to generate more than 14 megawatts of electricity from landfill gas, preventing 89,000 metric tons of carbon dioxide emissions per year from entering the atmosphere. That emissions savings equates to more than 18,500 passenger vehicles per year.

Landfill gas is a mix of different gases produced from the chemical reactions and effects of microbes on waste products. Between 40 and 60 percent of the gas is methane, while much of the remainder is made up of carbon dioxide, and traces of other gases.

Separating natural gas from the other gases makes it possible to be used in facilities such as GM's assembly plants.

Top 10 Movie Star Cars: Photos

Not only does this reduce the output of waste gases into the atmosphere, but also reduces the need for gas from fossil fuels. It's also cheaper than other fuels. General Motors expects to save a combined $10 million in energy costs each year at its facilities.

The Orion, Mich., plant has actually used landfill gas since 1999 to heat a portion of the paint shop. By the time the new equipment is installed, landfill gas will account for 54 percent of Orion's energy usage. At the Fort Wayne, Ind., facility, the gas will cover 40 percent of the plant's energy usage.

"...allows us to act as our own utility," explains Bill Mortimer, GM co-generation project manager. “Not only does this help us save on energy costs, but it limits the amount of greenhouse gas released into the atmosphere.”

GM has previously explored other green energy technologies to reduce costs and emissions. At the automaker's Detroit-Hamtramck facility, which produces the Chevrolet Volt, a 264,000 square-foot solar array helps power portions of the plant, saving an estimated $15,000 per year.

Other automakers such as Honda and Nissan have also explored alternative energies at their factories -- such as solar arrays and wind turbines.

Get more from Green Car Reports

  • All-In-One Wheel For E-Bicycles: Battery Two-Wheelers To Swamp Electric Cars?

  • Pricing Carbon Emissions? Bring It On, Say Some Large Companies

  • Suzuki Every Electric Car Does 800 Miles, Sets New Japanese Range Record

This article originally appeared on Green Car Reports, a HighGear Media company. All rights reserved.