07/21/2006 AT 07:55 AM EDT
Like her Oscar-winning character Erin Brockovich, Julia Roberts is on an environmental mission.
The 38-year-old actress has agreed to become a spokesperson for Earth Biofuels, a company that develops renewable energies like biodiesel and ethanol. "It's very important that we expand our use of clean energy and make a long-term commitment to it," Roberts said. "Biodiesel and ethanol are better for the environment and for the air we breathe."
Roberts brings superstar wattage to the efforts to broaden awareness of biofuels. She joins fellow Oscar winner Morgan Freeman and country-music legend Willie Nelson, who are both on Earth Biofuels' board of directors.
In one of her first jobs for the company, Roberts will join the push to get the 500,000 diesel-burning school buses in America to switch to clean-burning biodiesel. "The use of biodiesel is a positive step toward minimizing pollutive emissions and greenhouse gases," Roberts said. "By focusing on school buses, we can affect the health and well-being of the people most susceptible to that pollution – our children – today."
Roberts and her husband, cinematographer Danny Moder, gave birth to twins Hazel and Phinnaeus in November 2004. The star won an Academy Award in 2001 for her portrayal of Brockovich, the single mother who uncovered illegal dumping of toxic waste by the Pacific Gas & Electric company.
"I really admire Erin for fighting for what she believed in," Roberts told PEOPLE in 2000. "Few people do. Part of me wished I could be more like her."