The tiny biodiesel industry has gotten a big boost from Big Oil.

Houston-based refiner Motiva Enterprises announced yesterday that it's begun blending the soy-based alternative with traditional motor fuel at its Dallas terminal.

Biodiesel's supporters -- including country singer Willie Nelson -- say the impact is more than symbolic. Nelson and actor Morgan Freeman are both members of Dallas-based Earth Biofuels' board of directors. Earth Biofuels is providing the biofuel for blending with Motiva's diesel fuel.

Earth Biofuels Chairman Dennis McGlaughlin says this is the first time a biodiesel business has begun working with a large energy company. He and other industry officials say the collaboration will bring more credibility to biodiesel.

Biodiesel still accounts for a tiny fraction of the fuels the nation consumes.

Motiva's a partnership between Shell Oil and Saudi Refining.