Mine operator Alpha Natural Resources says it is buying a stake in a company that makes environmentally-friendly cement from fly ash left after burning coal.

Alpha announced the deal with Alexandria, Va-based Ceratech Inc on Monday. The company says it will start with a 10.3%stake in Ceratech, with an option to acquire up to 28.3%.

Alpha says Ceratech makes so-called "green cement" that uses 95% waste fly ash from power plants. The process reduces the amount of ash going into landfills and generates no emissions of carbon dioxide, the chief gas linked to climate change.

Abingdon-based Alpha operates mines in Virginia, West Virginia, Pennsylvania, Kentucky, Pennsylvania and Wyoming.