The U.S. Environmental Protection Agency approved permits for the FutureGen clean coal project to store carbon dioxide underground.

The permits approved Tuesday are a key piece of the project. FutureGen aims to capture carbon dioxide from coal at a power plant in western Illinois and store it. Carbon dioxide is a greenhouse gas linked to climate change.

The EPA said the permits are the first of this type for carbon sequestration.

FutureGen Alliance CEO Ken Humphreys called the permits a major milestone.

The alliance has said construction recently started on parts of its long-planned $1.6 billion project in Meredosia, Illinois The U.S. Department of Energy is providing $1 billion.

The project still faces a complaint filed by the Sierra Club with the Illinois Pollution Control Board over potential air pollution.