Houston-based Waste Management [1] (NYSE: WMI [2]) has a lot of landfills and wants to do something with them.

The company announced plans yesterday to turn 60 of those waste sites into renewable energy facilities over the next five years.

Waste Management is the largest landfill operator in the U.S., with 281 landfills.

"This national initiative is a major step in Waste Management's ongoing efforts to implement sustainable business practices across the company," said Paul Pabor, VP of renewable energy at Waste Management.

"We're building on the success of our existing local facilities, using the experience we've gathered from over 20 years of developing landfill gas to energy projects to carry out the national 5 year program," said Pabor.

Waste Management opened its first landfill gas to energy facility in the U.S. more than 20 years ago.

The company said the new plants will capture methane gas from decomposing landfill waste, generating more than 700 megawatts of electricity, enough to power 700,000 homes.

Landfill gas, produced when microorganisms break down organic material in the landfill, is comprised of approximately 50 to 60 percent methane and 40 to 50 percent carbon dioxide.

The company said that at most landfills in the U.S., these greenhouse gases are simply burned off.

At Waste Management sites with landfill gas to energy facilities, the company said the methane is collected and used to fuel on-site engines or turbines.